I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s
has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >semiconductors.
multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the
oscillator with a tuned circuit but can only get a couple of volts
pk/pk. This isn't enough to drive the ECC91, which I had hoped could
be used as a 'push-push' doubler, it also won't drive an EF91 over
enough of the curved portion of its characteristic to give sufficient >frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in
the anode of the xtal oscillator to drive one of the triodes of the
ECC91 which can then act as the multiplier. There is a whopping great
15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and,
with the cathode earthed, this develops enough grid-leak bias that the
valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have
given a large signal at 75 Mc/s in an anode circuit tuned to that
frequency - but it doesn't appear to. I can't use the triodes as
straight earthed-cathode amplifiers at those frequencies because of the >Miller capacitance effect, but they should be perfectly satisfactory as >multipliers where the grid and anode circuits are tuned to different >frequencies.
Does anyone know how to determine the optimum conditions for generating
the 5th and 2nd harmionics in valves?
On Fri, 31 Jan 2025 13:51:25 +0000, [email protected]d[...]
(Liz Tuddenham) wrote:
The whole thing must be done with the minimum number of valves and no >semiconductors.
Why?
The Colpitts-derived xtal oscillator is an EF91 and the
multiplier stage(s) can be either another EF91 or an ECC91.
Why not use a 150 MHz xtal?
Does anyone know how to determine the optimum conditions for generating
the 5th and 2nd harmionics in valves?
One dual triode could make two injection-locked oscillators.
On Fri, 31 Jan 2025 13:51:25 +0000, [email protected]d
(Liz Tuddenham) wrote:
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >>signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s
has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >>semiconductors.
Why?
The Colpitts-derived xtal oscillator is an EF91 and the
multiplier stage(s) can be either another EF91 or an ECC91.
Why not use a 150 MHz xtal?
I have tried picking the x5 signal (75 Mc/s) off the anode of the >>oscillator with a tuned circuit but can only get a couple of volts
pk/pk. This isn't enough to drive the ECC91, which I had hoped could
be used as a 'push-push' doubler, it also won't drive an EF91 over
enough of the curved portion of its characteristic to give sufficient >>frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in >>the anode of the xtal oscillator to drive one of the triodes of the
ECC91 which can then act as the multiplier. There is a whopping great
15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and, >>with the cathode earthed, this develops enough grid-leak bias that the >>valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have >>given a large signal at 75 Mc/s in an anode circuit tuned to that
frequency - but it doesn't appear to. I can't use the triodes as
straight earthed-cathode amplifiers at those frequencies because of the >>Miller capacitance effect, but they should be perfectly satisfactory as >>multipliers where the grid and anode circuits are tuned to different >>frequencies.
Does anyone know how to determine the optimum conditions for generating
the 5th and 2nd harmionics in valves?
One dual triode could make two injection-locked oscillators.
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s
has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >semiconductors. The Colpitts-derived xtal oscillator is an EF91 and the >multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the
oscillator with a tuned circuit but can only get a couple of volts
pk/pk. This isn't enough to drive the ECC91, which I had hoped could
be used as a 'push-push' doubler, it also won't drive an EF91 over
enough of the curved portion of its characteristic to give sufficient >frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in
the anode of the xtal oscillator to drive one of the triodes of the
ECC91 which can then act as the multiplier. There is a whopping great
15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and,
with the cathode earthed, this develops enough grid-leak bias that the
valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have
given a large signal at 75 Mc/s in an anode circuit tuned to that
frequency - but it doesn't appear to. I can't use the triodes as
straight earthed-cathode amplifiers at those frequencies because of the >Miller capacitance effect, but they should be perfectly satisfactory as >multipliers where the grid and anode circuits are tuned to different >frequencies.
Does anyone know how to determine the optimum conditions for generating
the 5th and 2nd harmionics in valves?
On Fri, 31 Jan 2025 13:51:25 +0000, [email protected]d
(Liz Tuddenham) wrote:
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >>signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s
has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >>semiconductors. The Colpitts-derived xtal oscillator is an EF91 and the >>multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the >>oscillator with a tuned circuit but can only get a couple of volts
pk/pk. This isn't enough to drive the ECC91, which I had hoped could
be used as a 'push-push' doubler, it also won't drive an EF91 over
enough of the curved portion of its characteristic to give sufficient >>frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in >>the anode of the xtal oscillator to drive one of the triodes of the
ECC91 which can then act as the multiplier. There is a whopping great
15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and, >>with the cathode earthed, this develops enough grid-leak bias that the >>valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have >>given a large signal at 75 Mc/s in an anode circuit tuned to that
frequency - but it doesn't appear to. I can't use the triodes as
straight earthed-cathode amplifiers at those frequencies because of the >>Miller capacitance effect, but they should be perfectly satisfactory as >>multipliers where the grid and anode circuits are tuned to different >>frequencies.
Does anyone know how to determine the optimum conditions for generating
the 5th and 2nd harmionics in valves?
Nowadays, just ask AI!
Generating 2nd and 5th harmonics from a thermionic (vacuum) tube
involves specific operational conditions and circuit configurations.
Here's how you can achieve this:
Conditions for 2nd Harmonic Generation:
Non-linear Operation:
Grid Bias: The tube should be biased to operate in a
non-linear part of its characteristic curve. This typically means
biasing the grid slightly negative so that the tube's operation swings
into the non-linear regions of the plate current-grid voltage
characteristic.
Signal Amplitude: The input signal should be of sufficient
amplitude to drive the tube beyond its linear operating region,
causing even harmonics (like the 2nd) to be generated due to the
non-linear response of the tube.
Circuit Configuration:
Single-ended Amplifier: A simple single-ended triode or
pentode amplifier can naturally produce even harmonics if driven into >non-linearity.
Cathode Bias: Using cathode bias can help in achieving the
desired non-linear operation by introducing a dynamic bias that
changes with signal level.
Conditions for 5th Harmonic Generation:
Non-linearity and Symmetry:
Higher Order Distortion: The 5th harmonic is an odd harmonic,
which means the tube's operation needs to be asymmetrical around zero
to produce it effectively. However, tubes naturally produce less odd >harmonics than even ones unless manipulated.
Signal Drive: A very strong input signal might push the tube
into regions where higher-order harmonics become significant, but this >approach might also introduce unwanted distortion.
Circuit Techniques:
Feedback: Using feedback in the right way can amplify certain
harmonics. Negative feedback can reduce even harmonics while
potentially emphasizing odd ones if designed for such.
Multiple Stages: Cascading multiple tube stages can increase
the harmonic content by compounding the distortion at each stage. Each
stage could be designed to push further into non-linearity.
Harmonic Enhancement Circuits: Specific circuits like those
with transformer coupling where the primary and secondary windings' >interaction can be tuned for harmonic enhancement. Also, using
resonant circuits or filters tuned to the 5th harmonic can help.
Tube Selection:
Tube Characteristics: Some tubes are naturally more harmonic
rich than others. Tubes like the 12AX7 might be used for their gain
and non-linearity characteristics, but for more harmonic richness,
sometimes pentodes or specific triodes known for distortion
characteristics are employed.
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Power Supply Design:
Power Supply Stiffness: A less stiff (or intentionally loose)
power supply can allow tube operation to vary more with the signal, >potentially increasing harmonic distortion.
In practice, generating a specific harmonic like the 5th is
challenging because tubes are inherently more suited to producing even >harmonics when driven hard.
To get a pronounced 5th harmonic, you'd
often need to tailor the circuit design, including feedback, load >characteristics, and perhaps even use of additional harmonic
generators or filters post-amplification.
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>
wrote:
On Fri, 31 Jan 2025 13:51:25 +0000, [email protected]d
(Liz Tuddenham) wrote:
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >>>signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s >>>has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >>>semiconductors. The Colpitts-derived xtal oscillator is an EF91 and the >>>multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the >>>oscillator with a tuned circuit but can only get a couple of volts
pk/pk. This isn't enough to drive the ECC91, which I had hoped could
be used as a 'push-push' doubler, it also won't drive an EF91 over
enough of the curved portion of its characteristic to give sufficient >>>frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in >>>the anode of the xtal oscillator to drive one of the triodes of the
ECC91 which can then act as the multiplier. There is a whopping great
15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and, >>>with the cathode earthed, this develops enough grid-leak bias that the >>>valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have >>>given a large signal at 75 Mc/s in an anode circuit tuned to that >>>frequency - but it doesn't appear to. I can't use the triodes as >>>straight earthed-cathode amplifiers at those frequencies because of the >>>Miller capacitance effect, but they should be perfectly satisfactory as >>>multipliers where the grid and anode circuits are tuned to different >>>frequencies.
Does anyone know how to determine the optimum conditions for generating >>>the 5th and 2nd harmionics in valves?
Nowadays, just ask AI!
Generating 2nd and 5th harmonics from a thermionic (vacuum) tube
involves specific operational conditions and circuit configurations.
Here's how you can achieve this:
Conditions for 2nd Harmonic Generation:
Non-linear Operation:
Grid Bias: The tube should be biased to operate in a
non-linear part of its characteristic curve. This typically means
biasing the grid slightly negative so that the tube's operation swings
into the non-linear regions of the plate current-grid voltage >>characteristic.
Signal Amplitude: The input signal should be of sufficient >>amplitude to drive the tube beyond its linear operating region,
causing even harmonics (like the 2nd) to be generated due to the
non-linear response of the tube.
Circuit Configuration:
Single-ended Amplifier: A simple single-ended triode or
pentode amplifier can naturally produce even harmonics if driven into >>non-linearity.
Cathode Bias: Using cathode bias can help in achieving the
desired non-linear operation by introducing a dynamic bias that
changes with signal level.
Crazy.
Conditions for 5th Harmonic Generation:
Non-linearity and Symmetry:
Higher Order Distortion: The 5th harmonic is an odd harmonic,
which means the tube's operation needs to be asymmetrical around zero
to produce it effectively. However, tubes naturally produce less odd >>harmonics than even ones unless manipulated.
Signal Drive: A very strong input signal might push the tube
into regions where higher-order harmonics become significant, but this >>approach might also introduce unwanted distortion.
Dumb AI. We WANT distortion. Specifically about a 10% plate conduction
duty cycle.
Circuit Techniques:
Feedback: Using feedback in the right way can amplify certain >>harmonics. Negative feedback can reduce even harmonics while
potentially emphasizing odd ones if designed for such.
Multiple Stages: Cascading multiple tube stages can increase
the harmonic content by compounding the distortion at each stage. Each >>stage could be designed to push further into non-linearity.
Harmonic Enhancement Circuits: Specific circuits like those
with transformer coupling where the primary and secondary windings' >>interaction can be tuned for harmonic enhancement. Also, using
resonant circuits or filters tuned to the 5th harmonic can help.
Tube Selection:
Tube Characteristics: Some tubes are naturally more harmonic
rich than others. Tubes like the 12AX7 might be used for their gain
and non-linearity characteristics, but for more harmonic richness, >>sometimes pentodes or specific triodes known for distortion
characteristics are employed.
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
Power Supply Design:
Power Supply Stiffness: A less stiff (or intentionally loose)
power supply can allow tube operation to vary more with the signal, >>potentially increasing harmonic distortion.
In practice, generating a specific harmonic like the 5th is
challenging because tubes are inherently more suited to producing even >>harmonics when driven hard.
Why is that?
To get a pronounced 5th harmonic, you'd
often need to tailor the circuit design, including feedback, load >>characteristics, and perhaps even use of additional harmonic
generators or filters post-amplification.
AI platitudes, harvesting conventional wisdom.
On Fri, 31 Jan 2025 16:12:35 -0800, john larkin <[email protected]>
wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>wrote:
On Fri, 31 Jan 2025 13:51:25 +0000, [email protected]d
(Liz Tuddenham) wrote:
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >>>>signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s >>>>has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >>>>semiconductors. The Colpitts-derived xtal oscillator is an EF91 and the >>>>multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the >>>>oscillator with a tuned circuit but can only get a couple of volts >>>>pk/pk. This isn't enough to drive the ECC91, which I had hoped could >>>>be used as a 'push-push' doubler, it also won't drive an EF91 over >>>>enough of the curved portion of its characteristic to give sufficient >>>>frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in >>>>the anode of the xtal oscillator to drive one of the triodes of the >>>>ECC91 which can then act as the multiplier. There is a whopping great >>>>15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and, >>>>with the cathode earthed, this develops enough grid-leak bias that the >>>>valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have >>>>given a large signal at 75 Mc/s in an anode circuit tuned to that >>>>frequency - but it doesn't appear to. I can't use the triodes as >>>>straight earthed-cathode amplifiers at those frequencies because of the >>>>Miller capacitance effect, but they should be perfectly satisfactory as >>>>multipliers where the grid and anode circuits are tuned to different >>>>frequencies.
Does anyone know how to determine the optimum conditions for generating >>>>the 5th and 2nd harmionics in valves?
Nowadays, just ask AI!
Generating 2nd and 5th harmonics from a thermionic (vacuum) tube
involves specific operational conditions and circuit configurations. >>>Here's how you can achieve this:
Conditions for 2nd Harmonic Generation:
Non-linear Operation:
Grid Bias: The tube should be biased to operate in a
non-linear part of its characteristic curve. This typically means
biasing the grid slightly negative so that the tube's operation swings >>>into the non-linear regions of the plate current-grid voltage >>>characteristic.
Signal Amplitude: The input signal should be of sufficient >>>amplitude to drive the tube beyond its linear operating region,
causing even harmonics (like the 2nd) to be generated due to the >>>non-linear response of the tube.
Circuit Configuration:
Single-ended Amplifier: A simple single-ended triode or
pentode amplifier can naturally produce even harmonics if driven into >>>non-linearity.
Cathode Bias: Using cathode bias can help in achieving the >>>desired non-linear operation by introducing a dynamic bias that
changes with signal level.
Crazy.
Conditions for 5th Harmonic Generation:
Non-linearity and Symmetry:
Higher Order Distortion: The 5th harmonic is an odd harmonic, >>>which means the tube's operation needs to be asymmetrical around zero
to produce it effectively. However, tubes naturally produce less odd >>>harmonics than even ones unless manipulated.
Signal Drive: A very strong input signal might push the tube
into regions where higher-order harmonics become significant, but this >>>approach might also introduce unwanted distortion.
Dumb AI. We WANT distortion. Specifically about a 10% plate conduction
duty cycle.
Circuit Techniques:
Feedback: Using feedback in the right way can amplify certain >>>harmonics. Negative feedback can reduce even harmonics while
potentially emphasizing odd ones if designed for such.
Multiple Stages: Cascading multiple tube stages can increase
the harmonic content by compounding the distortion at each stage. Each >>>stage could be designed to push further into non-linearity.
Harmonic Enhancement Circuits: Specific circuits like those
with transformer coupling where the primary and secondary windings' >>>interaction can be tuned for harmonic enhancement. Also, using
resonant circuits or filters tuned to the 5th harmonic can help.
Tube Selection:
Tube Characteristics: Some tubes are naturally more harmonic
rich than others. Tubes like the 12AX7 might be used for their gain
and non-linearity characteristics, but for more harmonic richness, >>>sometimes pentodes or specific triodes known for distortion >>>characteristics are employed.
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
Power Supply Design:
Power Supply Stiffness: A less stiff (or intentionally loose) >>>power supply can allow tube operation to vary more with the signal, >>>potentially increasing harmonic distortion.
In practice, generating a specific harmonic like the 5th is
challenging because tubes are inherently more suited to producing even >>>harmonics when driven hard.
Why is that?
To get a pronounced 5th harmonic, you'd
often need to tailor the circuit design, including feedback, load >>>characteristics, and perhaps even use of additional harmonic
generators or filters post-amplification.
AI platitudes, harvesting conventional wisdom.
Well, there's AI and there's AI. The above was Grok. I did try to get
the 'new kid on the block' (DeepSeek) to regale us with its wisdom on
the subject, but it didn't seem to have any. Chat GPT might be worth >asking....
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the average grid voltage of that stage caused by the drive.
On 01/02/2025 10:50, Liz Tuddenham wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is around 2.5 mA, so the conduction period is about 10%.
If you can make it generate a 25v 15MHz square wave then you should have approximately 8v of 3rd harmonic and 5v of fifth harmonic (as well as
some even harmonics because of how real valves behave). Slight low pass filtering to discourage any higher harmonic content will help here.
What does the output waveform actually look like at 15MHz?
Does the valve have enough gain at 75MHz to cope with a tuned load?
ECC91 sounds like it ought to unless something else gets in the way.
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s
has to be distributed to two other units by a 120-ohm screened cable.
The whole thing must be done with the minimum number of valves and no >semiconductors. The Colpitts-derived xtal oscillator is an EF91 and the >multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the
oscillator with a tuned circuit but can only get a couple of volts
pk/pk. This isn't enough to drive the ECC91, which I had hoped could
be used as a 'push-push' doubler, it also won't drive an EF91 over
enough of the curved portion of its characteristic to give sufficient >frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in
the anode of the xtal oscillator to drive one of the triodes of the
ECC91 which can then act as the multiplier. There is a whopping great
15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and,
with the cathode earthed, this develops enough grid-leak bias that the
valve is conducting anode pulses of over 20 mA about 10% of the time.
I would have thought that under those conditions the triode would have
given a large signal at 75 Mc/s in an anode circuit tuned to that
frequency - but it doesn't appear to. I can't use the triodes as
straight earthed-cathode amplifiers at those frequencies because of the >Miller capacitance effect, but they should be perfectly satisfactory as >multipliers where the grid and anode circuits are tuned to different >frequencies.
Does anyone know how to determine the optimum conditions for generating
the 5th and 2nd harmionics in valves?
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >average grid voltage of that stage caused by the drive.
On Sat, 01 Feb 2025 00:21:10 +0000, Cursitor Doom <[email protected]>
wrote:
On Fri, 31 Jan 2025 16:12:35 -0800, john larkin <[email protected]> >>wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>>wrote:
On Fri, 31 Jan 2025 13:51:25 +0000, [email protected]d >>>>(Liz Tuddenham) wrote:
I am trying to use a 15 Mc/s crystal oscillator to generate a 150 Mc/s >>>>>signal, the obvious multiplication ratios are x5 and x2. The 150 Mc/s >>>>>has to be distributed to two other units by a 120-ohm screened cable. >>>>>
The whole thing must be done with the minimum number of valves and no >>>>>semiconductors. The Colpitts-derived xtal oscillator is an EF91 and the >>>>>multiplier stage(s) can be either another EF91 or an ECC91.
I have tried picking the x5 signal (75 Mc/s) off the anode of the >>>>>oscillator with a tuned circuit but can only get a couple of volts >>>>>pk/pk. This isn't enough to drive the ECC91, which I had hoped could >>>>>be used as a 'push-push' doubler, it also won't drive an EF91 over >>>>>enough of the curved portion of its characteristic to give sufficient >>>>>frequency-doubled signal.
Alternatively, I have tried using a parallel-tuned circuit at 15 Mc/s in >>>>>the anode of the xtal oscillator to drive one of the triodes of the >>>>>ECC91 which can then act as the multiplier. There is a whopping great >>>>>15 Mc/s signal going into the grid of the triode (about 25v pk/pk) and, >>>>>with the cathode earthed, this develops enough grid-leak bias that the >>>>>valve is conducting anode pulses of over 20 mA about 10% of the time. >>>>>
I would have thought that under those conditions the triode would have >>>>>given a large signal at 75 Mc/s in an anode circuit tuned to that >>>>>frequency - but it doesn't appear to. I can't use the triodes as >>>>>straight earthed-cathode amplifiers at those frequencies because of the >>>>>Miller capacitance effect, but they should be perfectly satisfactory as >>>>>multipliers where the grid and anode circuits are tuned to different >>>>>frequencies.
Does anyone know how to determine the optimum conditions for generating >>>>>the 5th and 2nd harmionics in valves?
Nowadays, just ask AI!
Generating 2nd and 5th harmonics from a thermionic (vacuum) tube >>>>involves specific operational conditions and circuit configurations. >>>>Here's how you can achieve this:
Conditions for 2nd Harmonic Generation:
Non-linear Operation:
Grid Bias: The tube should be biased to operate in a
non-linear part of its characteristic curve. This typically means >>>>biasing the grid slightly negative so that the tube's operation swings >>>>into the non-linear regions of the plate current-grid voltage >>>>characteristic.
Signal Amplitude: The input signal should be of sufficient >>>>amplitude to drive the tube beyond its linear operating region,
causing even harmonics (like the 2nd) to be generated due to the >>>>non-linear response of the tube.
Circuit Configuration:
Single-ended Amplifier: A simple single-ended triode or
pentode amplifier can naturally produce even harmonics if driven into >>>>non-linearity.
Cathode Bias: Using cathode bias can help in achieving the >>>>desired non-linear operation by introducing a dynamic bias that
changes with signal level.
Crazy.
Conditions for 5th Harmonic Generation:
Non-linearity and Symmetry:
Higher Order Distortion: The 5th harmonic is an odd harmonic, >>>>which means the tube's operation needs to be asymmetrical around zero >>>>to produce it effectively. However, tubes naturally produce less odd >>>>harmonics than even ones unless manipulated.
Signal Drive: A very strong input signal might push the tube >>>>into regions where higher-order harmonics become significant, but this >>>>approach might also introduce unwanted distortion.
Dumb AI. We WANT distortion. Specifically about a 10% plate conduction >>>duty cycle.
Circuit Techniques:
Feedback: Using feedback in the right way can amplify certain >>>>harmonics. Negative feedback can reduce even harmonics while >>>>potentially emphasizing odd ones if designed for such.
Multiple Stages: Cascading multiple tube stages can increase >>>>the harmonic content by compounding the distortion at each stage. Each >>>>stage could be designed to push further into non-linearity.
Harmonic Enhancement Circuits: Specific circuits like those >>>>with transformer coupling where the primary and secondary windings' >>>>interaction can be tuned for harmonic enhancement. Also, using
resonant circuits or filters tuned to the 5th harmonic can help.
Tube Selection:
Tube Characteristics: Some tubes are naturally more harmonic >>>>rich than others. Tubes like the 12AX7 might be used for their gain
and non-linearity characteristics, but for more harmonic richness, >>>>sometimes pentodes or specific triodes known for distortion >>>>characteristics are employed.
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>>cutoff can increase harmonic distortion since the tube's response >>>>becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
Power Supply Design:
Power Supply Stiffness: A less stiff (or intentionally loose) >>>>power supply can allow tube operation to vary more with the signal, >>>>potentially increasing harmonic distortion.
In practice, generating a specific harmonic like the 5th is
challenging because tubes are inherently more suited to producing even >>>>harmonics when driven hard.
Why is that?
To get a pronounced 5th harmonic, you'd
often need to tailor the circuit design, including feedback, load >>>>characteristics, and perhaps even use of additional harmonic
generators or filters post-amplification.
AI platitudes, harvesting conventional wisdom.
Well, there's AI and there's AI. The above was Grok. I did try to get
the 'new kid on the block' (DeepSeek) to regale us with its wisdom on
the subject, but it didn't seem to have any. Chat GPT might be worth >>asking....
Won't it "learn" from amateur posts to chat sites? Collect opinions?
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is >around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >average grid voltage of that stage caused by the drive.
From old school notes, 5th harmonic peaks at 50degrees conduction,
3rd at 80degrees.
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >average grid voltage of that stage caused by the drive.
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is >around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid
leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the
average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>>> cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the
average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
On 01/02/2025 15:40, Liz Tuddenham wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>>>> wrote:[...]
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>>>> cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA >>>> at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>>> average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the
price. No idea how good it's valve models are but I bet they do exist.
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>>>> wrote:[...]
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>>>> cutoff can increase harmonic distortion since the tube's response >>>>>> becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working. >>>> With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA >>>> at the positive peak of the grid swing. The average anode current is >>>> around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>>> average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the
price. No idea how good it's valve models are but I bet they do exist.
It has a triode, a tetrode, and a pentode. I haven't tried them, but
there are a zillion YouTube videos about LT Spice.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >> >>>>> wrote:[...]
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >> >>>>>> cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid
leak, the peak current for one triode of an ECC91 is around 20 - 30 mA >> >>>> at the positive peak of the grid swing. The average anode current is >> >>>> around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >> >>>> average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the
price. No idea how good it's valve models are but I bet they do exist.
It has a triode, a tetrode, and a pentode. I haven't tried them, but
there are a zillion YouTube videos about LT Spice.
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of
things come into play, including the material of the valveholder.
For me to find a version of Spice that works on my computer under OS8.6,
then learn to use it well enough to get any useable results would take
years - with almost no chance of the outcome working any better than if
I had guessed at the component values to start with.
On Sat, 1 Feb 2025 21:53:43 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point: Grid Voltage: Adjusting the grid voltage to
operate closer to cutoff can increase harmonic distortion since
the tube's response becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be
working. With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid
and a 22k grid leak, the peak current for one triode of an ECC91
is around 20 - 30 mA at the positive peak of the grid swing. The
average anode current is around 2.5 mA, so the conduction period
is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in
the average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the
price. No idea how good it's valve models are but I bet they do exist.
It has a triode, a tetrode, and a pentode. I haven't tried them, but
there are a zillion YouTube videos about LT Spice.
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of
things come into play, including the material of the valveholder.
Tubes have model files, and you can adjust various parameters.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 21:53:43 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:It has a triode, a tetrode, and a pentode. I haven't tried them, but
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d >> >> >>> (Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point: Grid Voltage: Adjusting the grid voltage to >> >> >>>>>> operate closer to cutoff can increase harmonic distortion since
the tube's response becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude >> >> >>>>> drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be
working. With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid >> >> >>>> and a 22k grid leak, the peak current for one triode of an ECC91
is around 20 - 30 mA at the positive peak of the grid swing. The
average anode current is around 2.5 mA, so the conduction period
is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so >> >> >>>> little drive to the following stage that I can't see any change in >> >> >>>> the average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the
price. No idea how good it's valve models are but I bet they do exist. >> >>
there are a zillion YouTube videos about LT Spice.
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of
things come into play, including the material of the valveholder.
Tubes have model files, and you can adjust various parameters.
I don't know the parameters that I need for this job, the valve manuals
only publish static figures and some basic curves. Finding out things
like the gm of an EF91 when the signal is applied to G2 or G3 is almost >impossible as an academic exercise, it is quicker to solder up a test
rig and get the answer by experiment.
On Sun, 2 Feb 2025 08:00:09 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 21:53:43 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:It has a triode, a tetrode, and a pentode. I haven't tried them, but >>>>> there are a zillion YouTube videos about LT Spice.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d >>>>>>>> (Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point: Grid Voltage: Adjusting the grid voltage to >>>>>>>>>>> operate closer to cutoff can increase harmonic distortion since >>>>>>>>>>> the tube's response becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude >>>>>>>>>> drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be
working. With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid >>>>>>>>> and a 22k grid leak, the peak current for one triode of an ECC91 >>>>>>>>> is around 20 - 30 mA at the positive peak of the grid swing. The >>>>>>>>> average anode current is around 2.5 mA, so the conduction period >>>>>>>>> is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so >>>>>>>>> little drive to the following stage that I can't see any change in >>>>>>>>> the average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the >>>>>> price. No idea how good it's valve models are but I bet they do exist. >>>>>
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of
things come into play, including the material of the valveholder.
Tubes have model files, and you can adjust various parameters.
I don't know the parameters that I need for this job, the valve manuals
only publish static figures and some basic curves. Finding out things
like the gm of an EF91 when the signal is applied to G2 or G3 is almost
impossible as an academic exercise, it is quicker to solder up a test
rig and get the answer by experiment.
Then create your own Spice model from it. That's what the late great
Jim Thompson used to do very frequently. He was our go-to guy here for anything to do with constructing models. Sadly missed <sigh...>
Cursitor Doom <[email protected]> wrote:
On Sun, 2 Feb 2025 08:00:09 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 21:53:43 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:It has a triode, a tetrode, and a pentode. I haven't tried them, but >>>>>> there are a zillion YouTube videos about LT Spice.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d >>>>>>>>> (Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:Spice it!
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point: Grid Voltage: Adjusting the grid voltage to >>>>>>>>>>>> operate closer to cutoff can increase harmonic distortion since >>>>>>>>>>>> the tube's response becomes more non-linear near cutoff. >>>>>>>>>>>Operate it deep in cutoff, off most of the time. A high amplitude >>>>>>>>>>> drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be >>>>>>>>>> working. With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid >>>>>>>>>> and a 22k grid leak, the peak current for one triode of an ECC91 >>>>>>>>>> is around 20 - 30 mA at the positive peak of the grid swing. The >>>>>>>>>> average anode current is around 2.5 mA, so the conduction period >>>>>>>>>> is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so >>>>>>>>>> little drive to the following stage that I can't see any change in >>>>>>>>>> the average grid voltage of that stage caused by the drive. >>>>>>>>>
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the >>>>>>> price. No idea how good it's valve models are but I bet they do exist. >>>>>>
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of
things come into play, including the material of the valveholder.
Tubes have model files, and you can adjust various parameters.
I don't know the parameters that I need for this job, the valve manuals
only publish static figures and some basic curves. Finding out things
like the gm of an EF91 when the signal is applied to G2 or G3 is almost
impossible as an academic exercise, it is quicker to solder up a test
rig and get the answer by experiment.
Then create your own Spice model from it. That's what the late great
Jim Thompson used to do very frequently. He was our go-to guy here for
anything to do with constructing models. Sadly missed <sigh...>
Last February would have been his 21st birthday.
Cheers
Phil Hobbs
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed
an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904
Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 Mc/s, which should be relatively easy.
Revised block diagram at: http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not
be any more difficult but I may require an extra tuned circuit in the
later part of the transmitting chain to reduce the level of image
frequency.
I just hope the new crystal will work in the same circuit as the old one
and I won't have all the hassle of redesigning it.
On 1.2.2025 17.30, Liz Tuddenham wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed
an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904 Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 Mc/s, which should be relatively easy.
Revised block diagram at: http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not
be any more difficult but I may require an extra tuned circuit in the
later part of the transmitting chain to reduce the level of image frequency.
I just hope the new crystal will work in the same circuit as the old one and I won't have all the hassle of redesigning it.
Liz: You should not attempt to transmit anything around 150 MHz. It is
on a frequency band reserved for satellite communication, and any
unlicensed transmission is strongly frowned at.
Tauno Voipio <[email protected]d> wrote:
On 1.2.2025 17.30, Liz Tuddenham wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get >>>> you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed
an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904
Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 >>> Mc/s, which should be relatively easy.
Revised block diagram at:
http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more >>> difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not
be any more difficult but I may require an extra tuned circuit in the
later part of the transmitting chain to reduce the level of image
frequency.
I just hope the new crystal will work in the same circuit as the old one >>> and I won't have all the hassle of redesigning it.
Liz: You should not attempt to transmit anything around 150 MHz. It is
on a frequency band reserved for satellite communication, and any
unlicensed transmission is strongly frowned at.
I am being very careful to avoid transmitting any spurious signals at
150 Mc/s; the U.K. Amateur Radio band is 144 - 146 Mc/s and I am only allowed to transmit within that band.
The block diagram (referred to above) shows that the 150 Mc/s output of
the multiplier chain is mixed with the output of a variable frequency oscillator to give a signal in the 144 - 146 Mc/s band. A balanced
mixer should attenuate the 150 Mc/s signal and further filtering removes
any remaining residual 150 Mc/s and the image freqency (164 - 166 Mc/s).
In an earlier design I proposed a low-side input to the mixer at 135
Mc/s but abandoned this when I realise that the image would be 124 - 126 Mc/s:. This is in the band allocated to aircraft and I live undeneath
the flight path to Bristol Airport.
On 2.2.2025 23.10, Liz Tuddenham wrote:
Tauno Voipio <[email protected]d> wrote:
On 1.2.2025 17.30, Liz Tuddenham wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get >>>> you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed >>> an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904 >>> Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 >>> Mc/s, which should be relatively easy.
Revised block diagram at:
http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more >>> difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not >>> be any more difficult but I may require an extra tuned circuit in the
later part of the transmitting chain to reduce the level of image
frequency.
I just hope the new crystal will work in the same circuit as the old one >>> and I won't have all the hassle of redesigning it.
Liz: You should not attempt to transmit anything around 150 MHz. It is
on a frequency band reserved for satellite communication, and any
unlicensed transmission is strongly frowned at.
I am being very careful to avoid transmitting any spurious signals at
150 Mc/s; the U.K. Amateur Radio band is 144 - 146 Mc/s and I am only allowed to transmit within that band.
The block diagram (referred to above) shows that the 150 Mc/s output of
the multiplier chain is mixed with the output of a variable frequency oscillator to give a signal in the 144 - 146 Mc/s band. A balanced
mixer should attenuate the 150 Mc/s signal and further filtering removes any remaining residual 150 Mc/s and the image freqency (164 - 166 Mc/s).
In an earlier design I proposed a low-side input to the mixer at 135
Mc/s but abandoned this when I realise that the image would be 124 - 126 Mc/s:. This is in the band allocated to aircraft and I live undeneath
the flight path to Bristol Airport.
You're starting with a too low IF. The standard method for 2 meter transverters is to start with a 28 MHz band signal, to get the images
far enough to use less complicated filters after mixing. You have to
be careful about oscillator signal leaking through the mixing process
anyway.
The 160 MHz bands are for maritime mobile services.
<nag>
Megacycles / second have been buried even in the US for over half a
century. The current radios use MHz or GHz.
</nag>
Tauno Voipio <[email protected]d> wrote:
On 2.2.2025 23.10, Liz Tuddenham wrote:
Tauno Voipio <[email protected]d> wrote:
On 1.2.2025 17.30, Liz Tuddenham wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get >>>>>> you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed >>>>> an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904 >>>>> Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 >>>>> Mc/s, which should be relatively easy.
Revised block diagram at:
http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more >>>>> difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not >>>>> be any more difficult but I may require an extra tuned circuit in the >>>>> later part of the transmitting chain to reduce the level of image
frequency.
I just hope the new crystal will work in the same circuit as the old one >>>>> and I won't have all the hassle of redesigning it.
Liz: You should not attempt to transmit anything around 150 MHz. It is >>>> on a frequency band reserved for satellite communication, and any
unlicensed transmission is strongly frowned at.
I am being very careful to avoid transmitting any spurious signals at
150 Mc/s; the U.K. Amateur Radio band is 144 - 146 Mc/s and I am only
allowed to transmit within that band.
The block diagram (referred to above) shows that the 150 Mc/s output of
the multiplier chain is mixed with the output of a variable frequency
oscillator to give a signal in the 144 - 146 Mc/s band. A balanced
mixer should attenuate the 150 Mc/s signal and further filtering removes >>> any remaining residual 150 Mc/s and the image freqency (164 - 166 Mc/s). >>>
In an earlier design I proposed a low-side input to the mixer at 135
Mc/s but abandoned this when I realise that the image would be 124 - 126 >>> Mc/s:. This is in the band allocated to aircraft and I live undeneath
the flight path to Bristol Airport.
You're starting with a too low IF. The standard method for 2 meter
transverters is to start with a 28 MHz band signal, to get the images
far enough to use less complicated filters after mixing. You have to
be careful about oscillator signal leaking through the mixing process
anyway.
My first 2 metre receiving setup had a crystal-controlled down-converter
and a CR100 communications receiver running at 28 Mc/s. The CR100 was
so unstable that it would shift several Kc/s if a gnat landed on the
front panel. I improved the mechanical design, which was very poor, and
made it useable but it was never particularly stable.
Using a VFO on the transmit side requires an even better degree of
stability, which is why I chose to keep the crystal-controlled frequency
high and use a more stable lower frequency VFO to generate the
transmitting frequency. The VFO coil is wound on a ceramic former and
bonded with epoxy resin to reduce expansion of the copper wire. I have
made provision for temperature compensation and checked that the
frequency drift with changes in the H.T. voltage are negligible.
On the receive side, the first down-conversion ratio is 145 to 5 Mc/s
i.e. 29:1, the second ratio is 5 Mc/s to 100 Kc/s i.e.50:1. If these
were stupidly different I would be very worried, but they aren't too far
off the ideal of both being 38:1 and the greater ratio is at the lower frequency, where filtering is easier.
The 160 MHz bands are for maritime mobile services.
Luckily I live far enough from the sea that my transmissions will never
get to the coast. If I go portable, the highest land is still some way inland and my maximum output is less than 10 Watts, so I don't think
there is likely to be much of a problem.
<nag>
Megacycles / second have been buried even in the US for over half a
century. The current radios use MHz or GHz.
</nag>
Yes, I know ...but I am well over half a century old and I prefer Mc/s.
Cursitor Doom <[email protected]> wrote:
On Sun, 2 Feb 2025 08:00:09 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 21:53:43 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:It has a triode, a tetrode, and a pentode. I haven't tried them, but >>>>>> there are a zillion YouTube videos about LT Spice.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d >>>>>>>>> (Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:Spice it!
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point: Grid Voltage: Adjusting the grid voltage to >>>>>>>>>>>> operate closer to cutoff can increase harmonic distortion since >>>>>>>>>>>> the tube's response becomes more non-linear near cutoff. >>>>>>>>>>>Operate it deep in cutoff, off most of the time. A high amplitude >>>>>>>>>>> drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be >>>>>>>>>> working. With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid >>>>>>>>>> and a 22k grid leak, the peak current for one triode of an ECC91 >>>>>>>>>> is around 20 - 30 mA at the positive peak of the grid swing. The >>>>>>>>>> average anode current is around 2.5 mA, so the conduction period >>>>>>>>>> is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so >>>>>>>>>> little drive to the following stage that I can't see any change in >>>>>>>>>> the average grid voltage of that stage caused by the drive. >>>>>>>>>
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the >>>>>>> price. No idea how good it's valve models are but I bet they do exist. >>>>>>
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of
things come into play, including the material of the valveholder.
Tubes have model files, and you can adjust various parameters.
I don't know the parameters that I need for this job, the valve manuals
only publish static figures and some basic curves. Finding out things
like the gm of an EF91 when the signal is applied to G2 or G3 is almost
impossible as an academic exercise, it is quicker to solder up a test
rig and get the answer by experiment.
Then create your own Spice model from it. That's what the late great
Jim Thompson used to do very frequently. He was our go-to guy here for
anything to do with constructing models. Sadly missed <sigh...>
Last February would have been his 21st birthday.
Cheers
Phil Hobbs
On 2/2/2025 11:49 AM, Phil Hobbs wrote:
Cursitor Doom <[email protected]> wrote:
On Sun, 2 Feb 2025 08:00:09 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 21:53:43 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:
On 01/02/2025 15:40, Liz Tuddenham wrote:It has a triode, a tetrode, and a pentode. I haven't tried them, but >>>>>>> there are a zillion YouTube videos about LT Spice.
john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d >>>>>>>>>> (Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:Spice it!
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point: Grid Voltage: Adjusting the grid voltage to >>>>>>>>>>>>> operate closer to cutoff can increase harmonic distortion since >>>>>>>>>>>>> the tube's response becomes more non-linear near cutoff. >>>>>>>>>>>>Operate it deep in cutoff, off most of the time. A high amplitude >>>>>>>>>>>> drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be >>>>>>>>>>> working. With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid >>>>>>>>>>> and a 22k grid leak, the peak current for one triode of an ECC91 >>>>>>>>>>> is around 20 - 30 mA at the positive peak of the grid swing. The >>>>>>>>>>> average anode current is around 2.5 mA, so the conduction period >>>>>>>>>>> is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so >>>>>>>>>>> little drive to the following stage that I can't see any change in >>>>>>>>>>> the average grid voltage of that stage caused by the drive. >>>>>>>>>>
LT Spice has tube models.
...but I haven't got Spice.
LT Spice is free and works very well indeed. And you can't beat the >>>>>>>> price. No idea how good it's valve models are but I bet they do exist. >>>>>>>
I'm afraid that doesn't sound very promising. A triode could be
anything from a water-cooled UHF transmitting valve to a PX4 to a
1.5-volt battery-powered miniature audio type. At VHF all sorts of >>>>>> things come into play, including the material of the valveholder.
Tubes have model files, and you can adjust various parameters.
I don't know the parameters that I need for this job, the valve manuals >>>> only publish static figures and some basic curves. Finding out things >>>> like the gm of an EF91 when the signal is applied to G2 or G3 is almost >>>> impossible as an academic exercise, it is quicker to solder up a test
rig and get the answer by experiment.
Then create your own Spice model from it. That's what the late great
Jim Thompson used to do very frequently. He was our go-to guy here for
anything to do with constructing models. Sadly missed <sigh...>
Last February would have been his 21st birthday.
Cheers
Phil Hobbs
Yikes! (to quote JL) I'm 83+. Guess I Should start eating healthily.
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is >>around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed
an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904
Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 >Mc/s, which should be relatively easy.
Revised block diagram at: >http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more >difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not
be any more difficult but I may require an extra tuned circuit in the
later part of the transmitting chain to reduce the level of image
frequency.
I just hope the new crystal will work in the same circuit as the old one
and I won't have all the hassle of redesigning it.
On Sat, 1 Feb 2025 15:30:40 +0000, [email protected]d
(Liz Tuddenham) wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
I regret to say I think you are right :-(
Quintuplers just don't seem to work in those circuits so I have placed
an order for a 16.656 Mc/s crystal, which will triple-triple to 149.904 >>Mc/s. That will mean bringing the VFO down to a range of 3.904 to 5.904 >>Mc/s, which should be relatively easy.
Revised block diagram at: >>http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6a.gif
It will make image rejection in the second receiving mixer a little more >>difficult The transmitting mixer is intended to be balanced, so
rejecting 149.904 Mc/s instead of 150.000 Mc/s from the output will not
be any more difficult but I may require an extra tuned circuit in the
later part of the transmitting chain to reduce the level of image >>frequency.
I just hope the new crystal will work in the same circuit as the old one >>and I won't have all the hassle of redesigning it.
That should have been 6CX8 (6CM8)from the article.
There are functioning models for 6BL8 (ECF80), which
has a pentode/triode combination.
I expect just as big a problem in modeling would be in
coupling/filter magnetic components.
Oscillators never do . . . .
RL
Oscillators never do . . . .
On Sat, 01 Feb 2025 07:23:57 -0800, john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>> >cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>>leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is >>>around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>>average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
If Spice was of any use in RF ham gear, the amateur radio guys
would have been all over it three decades ago.
I've modeled known-good valve power cctry only as a curiosity, to
see if spice could come anywhere close to practical results.
Curiously the nowhere-near-common valves used already had models,
so I'm pretty sure somebody else had already made a run at the
identical application. (Tek HV oscillator).
RL
On Sat, 01 Feb 2025 07:23:57 -0800, john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]>[...]
wrote:
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>>> cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the
average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
If Spice was of any use in RF ham gear, the amateur radio guys
would have been all over it three decades ago.
I've modeled known-good valve power cctry only as a curiosity, to
see if spice could come anywhere close to practical results.
Curiously the nowhere-near-common valves used already had models,
so I'm pretty sure somebody else had already made a run at the
identical application. (Tek HV oscillator).
RL
On Tue, 04 Feb 2025 09:02:01 -0500, legg <[email protected]> wrote:
On Sat, 01 Feb 2025 07:23:57 -0800, john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>>>> wrote:[...]
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA >>>> at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>>> average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
If Spice was of any use in RF ham gear, the amateur radio guys
would have been all over it three decades ago.
RF design is still in the ancient days of load pulls and Smith charts
and slide rules. I expect that Qspice may change that. Everything
interesting is nonlinear.
I've modeled known-good valve power cctry only as a curiosity, to
see if spice could come anywhere close to practical results.
Curiously the nowhere-near-common valves used already had models,
so I'm pretty sure somebody else had already made a run at the
identical application. (Tek HV oscillator).
RL
Spice is great for modeling mosfets and phemts. Why not tubes?
legg <[email protected]> wrote:
[...]
Oscillators never do . . . .
Amplifiers oscillate . . . Oscillators don't.
john larkin <[email protected]> wrote:
On Tue, 04 Feb 2025 09:02:01 -0500, legg <[email protected]> wrote:
On Sat, 01 Feb 2025 07:23:57 -0800, john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>>>>> wrote:[...]
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to
cutoff can increase harmonic distortion since the tube's response >>>>>>> becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working. >>>>> With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>>>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA >>>>> at the positive peak of the grid swing. The average anode current is >>>>> around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>>>> average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
If Spice was of any use in RF ham gear, the amateur radio guys
would have been all over it three decades ago.
RF design is still in the ancient days of load pulls and Smith charts
and slide rules. I expect that Qspice may change that. Everything
interesting is nonlinear.
I've modeled known-good valve power cctry only as a curiosity, to
see if spice could come anywhere close to practical results.
Curiously the nowhere-near-common valves used already had models,
so I'm pretty sure somebody else had already made a run at the
identical application. (Tek HV oscillator).
RL
Spice is great for modeling mosfets and phemts. Why not tubes?
Electron transport needs integral equations, so transit time effects aren�t >reducible to a system of ODEs, which is what SPICE knows how to handle.
You can phony something up in a restricted range, e.g. the low frequency >limit.
Cheers
Phil Hobbs
On Tue, 4 Feb 2025 16:03:12 +0000, [email protected]d
(Liz Tuddenham) wrote:
legg <[email protected]> wrote:
[...]
Oscillators never do . . . .
Amplifiers oscillate . . . Oscillators don't.
Mine oscillate, sometimes at lots of different frequencies.
On 4.2.2025 16.02, legg wrote:
On Sat, 01 Feb 2025 07:23:57 -0800, john larkin <[email protected]> wrote:
On Sat, 1 Feb 2025 10:50:22 +0000, [email protected]d
(Liz Tuddenham) wrote:
john larkin <[email protected]> wrote:
On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <[email protected]> >>>>> wrote:[...]
Operating Point:
Grid Voltage: Adjusting the grid voltage to operate closer to >>>>>> cutoff can increase harmonic distortion since the tube's response
becomes more non-linear near cutoff.
Operate it deep in cutoff, off most of the time. A high amplitude
drive and grid-leak bias would be good.
That is exactly what I am doing and it doesn't appear to be working.
With 100v on the anode, 15 Mc/s at 25v pk/pk on the grid and a 22k grid >>>> leak, the peak current for one triode of an ECC91 is around 20 - 30 mA >>>> at the positive peak of the grid swing. The average anode current is
around 2.5 mA, so the conduction period is about 10%.
A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
little drive to the following stage that I can't see any change in the >>>> average grid voltage of that stage caused by the drive.
Spice it!
LT Spice has tube models.
If Spice was of any use in RF ham gear, the amateur radio guys
would have been all over it three decades ago.
I've modeled known-good valve power cctry only as a curiosity, to
see if spice could come anywhere close to practical results.
Curiously the nowhere-near-common valves used already had models,
so I'm pretty sure somebody else had already made a run at the
identical application. (Tek HV oscillator).
RL
I used, but well over half a century after the target device was built.
I designed and built a novice class CW transmitter in spring 1969. It
was used by several novices to get their required experience, and stored >after the novice class requirements were changed decades later. The >transmitter was found when the attic of my parents was cleaned.
The cleaning was done in 2020, at the worst COVID block-out time.
To do something useful, I created a description of the transmitter in
LaTeX, as an exercise. I used LTspice to draw the schematics, and as
a side product, a working model of the transmitter got born.
I had to create plenty of components, e.g. all tubes (EF94/6AU6,
EL83/6CK6, EL500/6GB5 and OA2/150C2). With extensive Internet search,
the matching Spice models were found, mostly from HiFi enthusiast
pages.
When running the models, I noticed that a real-world crystal model is
too slow to start, so I had to change it to lower Q, so that the solver
did not grow tired to start up. The simulated results matched quite well
with the built device, despite that in a transmitter, the tubes are
working well outside of the normal HiFi biasing range.
On 2/4/2025 9:50 PM, john larkin wrote:
On Tue, 4 Feb 2025 16:03:12 +0000, [email protected]d
(Liz Tuddenham) wrote:
legg <[email protected]> wrote:
[...]
Oscillators never do . . . .
Amplifiers oscillate . . . Oscillators don't.
Mine oscillate, sometimes at lots of different frequencies.
Simultaneously!?!
John S <[email protected]> wrote:
On 2/4/2025 9:50 PM, john larkin wrote:
On Tue, 4 Feb 2025 16:03:12 +0000, [email protected]d
(Liz Tuddenham) wrote:
legg <[email protected]> wrote:
[...]
Oscillators never do . . . .
Amplifiers oscillate . . . Oscillators don't.
Mine oscillate, sometimes at lots of different frequencies.
Simultaneously!?!
Q: What is the difference between squegging and a blocking oscillator?
A: A blocking oscillator is when you want it to happen.
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
You were right: with a crystal frequency of 16.656 Mc/s and two triplers
the results are much better.
New block diagram: <http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6c.gif>
New oscillator circuit: <http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc4c.gif>
The stages are: EF91 Reactance, EF91 Oscillator, ECC91 Tripler+ tripler.
The new crystal necessitated changes to the component values in the
'pulling' circuits, but the basic concept remain unchanged. Over large frequency swings the reactance valve characteristic appears curved but
with 0dBm audio input at 400 c/s there is no audible distortion and the frequency swing is around 15 Kc/s pk/pk, which is three times larger
than the permitted deviation in the amateur bands.
I tried putting a parallel-tuned circuit in the anode circuit of the oscillator, to resonate at the third harmonic, but there was very little signal, so I decided to use one triode of the ECC91 as the first
tripler. I then resonated the anode tuned circuit of the oscillator at crystal frequency but discovered that this made it unreliable at
start-up. Eventually I found that just an aperiodic [untuned] anode
choke gave plenty of drive to the grid of the first tripler and allowed
the oscillator to start reliably.
The parallel-tuned circuit of the first tripler and series-tuned circuit between the second tripler and the output cable both have comfortably
gentle tuning, which is an advantage because they should hold their
settings without adjustment for a long time. The output voltage is only around 300mV rms into 75 ohms, but this can be stepped up when it gets
to the mixer grids by a further resonant circuit.
On 9.2.2025 12.23, Liz Tuddenham wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
You were right: with a crystal frequency of 16.656 Mc/s and two triplers the results are much better.
New block diagram: <http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6c.gif>
New oscillator circuit: <http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc4c.gif>
The stages are: EF91 Reactance, EF91 Oscillator, ECC91 Tripler+ tripler.
The new crystal necessitated changes to the component values in the 'pulling' circuits, but the basic concept remain unchanged. Over large frequency swings the reactance valve characteristic appears curved but
with 0dBm audio input at 400 c/s there is no audible distortion and the frequency swing is around 15 Kc/s pk/pk, which is three times larger
than the permitted deviation in the amateur bands.
I tried putting a parallel-tuned circuit in the anode circuit of the oscillator, to resonate at the third harmonic, but there was very little signal, so I decided to use one triode of the ECC91 as the first
tripler. I then resonated the anode tuned circuit of the oscillator at crystal frequency but discovered that this made it unreliable at
start-up. Eventually I found that just an aperiodic [untuned] anode
choke gave plenty of drive to the grid of the first tripler and allowed
the oscillator to start reliably.
The parallel-tuned circuit of the first tripler and series-tuned circuit between the second tripler and the output cable both have comfortably gentle tuning, which is an advantage because they should hold their settings without adjustment for a long time. The output voltage is only around 300mV rms into 75 ohms, but this can be stepped up when it gets
to the mixer grids by a further resonant circuit.
Are you sure that the crystal lets you pulll it by 11 kHz and add angle modulation to it?
Please design and verify the 144 MHz transmit and receive filters
associated with the mixers for enough attenuation on the 150 MHz band.
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
You were right: with a crystal frequency of 16.656 Mc/s and two triplers
the results are much better.
New block diagram: ><http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6c.gif>
New oscillator circuit: ><http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc4c.gif>
The stages are: EF91 Reactance, EF91 Oscillator, ECC91 Tripler+ tripler.
The new crystal necessitated changes to the component values in the
'pulling' circuits, but the basic concept remain unchanged. Over large >frequency swings the reactance valve characteristic appears curved but
with 0dBm audio input at 400 c/s there is no audible distortion and the >frequency swing is around 15 Kc/s pk/pk, which is three times larger
than the permitted deviation in the amateur bands.
I tried putting a parallel-tuned circuit in the anode circuit of the >oscillator, to resonate at the third harmonic, but there was very little >signal, so I decided to use one triode of the ECC91 as the first
tripler. I then resonated the anode tuned circuit of the oscillator at >crystal frequency but discovered that this made it unreliable at
start-up. Eventually I found that just an aperiodic [untuned] anode
choke gave plenty of drive to the grid of the first tripler and allowed
the oscillator to start reliably.
The parallel-tuned circuit of the first tripler and series-tuned circuit >between the second tripler and the output cable both have comfortably
gentle tuning, which is an advantage because they should hold their
settings without adjustment for a long time. The output voltage is only >around 300mV rms into 75 ohms, but this can be stepped up when it gets
to the mixer grids by a further resonant circuit.
On Sun, 9 Feb 2025 10:23:28 +0000, [email protected]d
(Liz Tuddenham) wrote:
legg <[email protected]> wrote:
[...]
I'd be more selective of the crystal frequency. Two triplers might get
you there with a lot less grief.
You were right: with a crystal frequency of 16.656 Mc/s and two triplers >the results are much better.
New block diagram: ><http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6c.gif>
New oscillator circuit: ><http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc4c.gif>
The stages are: EF91 Reactance, EF91 Oscillator, ECC91 Tripler+ tripler.
The new crystal necessitated changes to the component values in the >'pulling' circuits, but the basic concept remain unchanged. Over large >frequency swings the reactance valve characteristic appears curved but
with 0dBm audio input at 400 c/s there is no audible distortion and the >frequency swing is around 15 Kc/s pk/pk, which is three times larger
than the permitted deviation in the amateur bands.
I tried putting a parallel-tuned circuit in the anode circuit of the >oscillator, to resonate at the third harmonic, but there was very little >signal, so I decided to use one triode of the ECC91 as the first
tripler. I then resonated the anode tuned circuit of the oscillator at >crystal frequency but discovered that this made it unreliable at
start-up. Eventually I found that just an aperiodic [untuned] anode
choke gave plenty of drive to the grid of the first tripler and allowed
the oscillator to start reliably.
The parallel-tuned circuit of the first tripler and series-tuned circuit >between the second tripler and the output cable both have comfortably >gentle tuning, which is an advantage because they should hold their >settings without adjustment for a long time. The output voltage is only >around 300mV rms into 75 ohms, but this can be stepped up when it gets
to the mixer grids by a further resonant circuit.
You seem to have got all your ducks in a row.
Tripling within the oscillator seems to have been pretty popular
back in the day. I'm not sure what kind of stress they were putting
on the crystal to do this, but they wanted >5V from a substituted
VCO to get similar downstream responses.
| Sysop: | Keyop |
|---|---|
| Location: | Huddersfield, West Yorkshire, UK |
| Users: | 715 |
| Nodes: | 16 (2 / 14) |
| Uptime: | 22:53:15 |
| Calls: | 12,105 |
| Calls today: | 5 |
| Files: | 15,006 |
| Messages: | 6,518,139 |
![http://www.poppyrecords.co.uk/other/Transceiver/Blockdiag5c.gif]](http://www.poppyrecords.co.uk/other/Transceiver/Blockdiag5c.gif]){kind=link}
![http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc3d.gif]](http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc3d.gif]){kind=link}
