So, I've been trying to figure out why my radio range is poor relative to my peers on my new-to-me ASH 31 Mi. While messing with SWR measurements and such, I used a cheap signal locator tool (inserts a tone into the cable and a hand wand picks it up) to
find where the radio antenna was located in the fin. This worked well, so for the heck of it, I went to do the same for the transponder.

It didn't work at all. The tone was killed as soon I hooked up the tone generator's leads to the connector's center conductor and the barrel. So I put my ohm meter on the connector and found it appeared shorted center pin to barrel with very low
resistance (0.1ohm). What?? As far as I knew, the transponder was working fine and I saw good ADSB tracking history last I looked a few months ago.

Assuming my manipulation of the instrument panel and cables caused a short in the connector, I disassembled it. No luck, no stray shield braid wires getting to the center conductor. Manipulation of the cable end does not affect the short. I have
access to about 1.5ft of the ~25ft cable before it dives into the inaccessible fuselage structure. While I want to suspect the short is in the last inch or so (where I saw the cable being severely bent coming out of the connector), I don't have enough
spare length to just start guessing and cutting. I actually just joined a HAM radio facebook group to ask for help (someone who can VNA/TDR the cable and maybe narrow down the short location).

Anyone out there with advice or a similar experience? I'm a retired electrical / automation engineer but my RF experience is weak. Is there any chance this 'short' is correct? The Trig TT22 installation manual indicates this should be a simple 50ohm
system with a high quality cable going into a dipole or antenna with a ground plane.

Truly dismayed and a bit overwhelmed to find this surprise issue. I can't imagine the hassle a deeply located short would be.

JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

I started thinking about this (dangerous) and started googling (more dangerous) to investigate antenna designs. I came across this:
It can be confusing but you have to consider that AC is different from DC, you are measuring (continuity)
with a meter at DC (direct current), and measuring resistance.

Radio (AC) functions differently and it is not resistance you are worried about but impedance (Z).
So that short circuit that you measure at DC is actually a complex impedance at the frequency it
is designed to operate at, it will have a capacitance and inductance such that it matches (and
couples) the RF energy efficiently into the radiating components of the antenna.
:
Think about a loop antenna (like a "Quad"), that is essentially a short circuit loop of wire, and if
you put a meter on it you just measure the resistance of the wire (at DC) but for RF the capacitance
and inductance of that wire is the dominant effect so instead of the RF turning into heat due to
resistance it is turned into electric and magnetic fields that radiate from the antenna as RF (EM radiation).

So, I do know the difference between impedance and resistance and this all makes sense (I just don't know squat about RF radiation and antennas). But I don't know if this 'DC short' is characteristic of the antenna in my glider. I assumed this was a
simple 'open circuit' dipole like the VHF radio but maybe it is actually a different configuration. Since my injected tone frequency is orders of magnitude lower than 1090MHz - it would appear as DC and die into the 'short' as well. Since my last
flight 10/29 showed very good ADSB coverage (and I can't come up for a good reason for this cable/antenna system to suddenly go bad) maybe it is just the DC characteristic of the antenna itself?

So, do I feel lucky? Should I go head and put it back together and run the transponder? Do any of you AS owners with a factory installed transponder antenna (2015 era) want to put an ohm meter on your transponder antenna cable for me?

In the meantime, maybe I can entice a local HAM with a free glider ride to bring their VNA rig over and test it for real.

JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 2:23:20 PM UTC-5, John Johnson wrote:

So, I've been trying to figure out why my radio range is poor relative to my peers on my new-to-me ASH 31 Mi. While messing with SWR measurements and such, I used a cheap signal locator tool (inserts a tone into the cable and a hand wand picks it up)

to find where the radio antenna was located in the fin. This worked well, so for the heck of it, I went to do the same for the transponder.

It didn't work at all. The tone was killed as soon I hooked up the tone generator's leads to the connector's center conductor and the barrel. So I put my ohm meter on the connector and found it appeared shorted center pin to barrel with very low

resistance (0.1ohm). What?? As far as I knew, the transponder was working fine and I saw good ADSB tracking history last I looked a few months ago.

Assuming my manipulation of the instrument panel and cables caused a short in the connector, I disassembled it. No luck, no stray shield braid wires getting to the center conductor. Manipulation of the cable end does not affect the short. I have access

to about 1.5ft of the ~25ft cable before it dives into the inaccessible fuselage structure. While I want to suspect the short is in the last inch or so (where I saw the cable being severely bent coming out of the connector), I don't have enough spare
length to just start guessing and cutting. I actually just joined a HAM radio facebook group to ask for help (someone who can VNA/TDR the cable and maybe narrow down the short location).

Anyone out there with advice or a similar experience? I'm a retired electrical / automation engineer but my RF experience is weak. Is there any chance this 'short' is correct? The Trig TT22 installation manual indicates this should be a simple 50ohm

system with a high quality cable going into a dipole or antenna with a ground plane.

Truly dismayed and a bit overwhelmed to find this surprise issue. I can't imagine the hassle a deeply located short would be.

JJ

I can mostly speak as a long time manufacture of wire and cable. What type of dialectic does it have, the layer between the center conductor and the outer shielding? If foam (expanded PE), a sharp bend can cause the center conductor to knife through the
dialectic, causing a short. Issue is, you bend it one way, it's fine, change the angle of bend by 90*, it's shorted as the conductor moved around. Do a continuity check while bending the wire sharply every 90* in the last few inches, see if the reading
changes.
Yep, we scrapped about 1,000,000 feet or RG-59 coax due to a tensioning issue in manufacturing. Spark test found some issues, but not all. Installed in new construction for cable TV. Shorts had us liable for removal, new cable, labor, fixing Sheetrock,
etc....Imwas plant manager at the time....sigh...
If a "semi solid" like a RG-62U, not as likely.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 4:26:35 PM UTC-5, John Johnson wrote:

I started thinking about this (dangerous) and started googling (more dangerous) to investigate antenna designs. I came across this:
It can be confusing but you have to consider that AC is different from DC, you are measuring (continuity)
with a meter at DC (direct current), and measuring resistance.

Radio (AC) functions differently and it is not resistance you are worried about but impedance (Z).
So that short circuit that you measure at DC is actually a complex impedance at the frequency it
is designed to operate at, it will have a capacitance and inductance such that it matches (and
couples) the RF energy efficiently into the radiating components of the antenna.
:
Think about a loop antenna (like a "Quad"), that is essentially a short circuit loop of wire, and if
you put a meter on it you just measure the resistance of the wire (at DC) but for RF the capacitance
and inductance of that wire is the dominant effect so instead of the RF turning into heat due to
resistance it is turned into electric and magnetic fields that radiate from the antenna as RF (EM radiation).

So, I do know the difference between impedance and resistance and this all makes sense (I just don't know squat about RF radiation and antennas). But I don't know if this 'DC short' is characteristic of the antenna in my glider. I assumed this was a

simple 'open circuit' dipole like the VHF radio but maybe it is actually a different configuration. Since my injected tone frequency is orders of magnitude lower than 1090MHz - it would appear as DC and die into the 'short' as well. Since my last flight
10/29 showed very good ADSB coverage (and I can't come up for a good reason for this cable/antenna system to suddenly go bad) maybe it is just the DC characteristic of the antenna itself?

So, do I feel lucky? Should I go head and put it back together and run the transponder? Do any of you AS owners with a factory installed transponder antenna (2015 era) want to put an ohm meter on your transponder antenna cable for me?

In the meantime, maybe I can entice a local HAM with a free glider ride to bring their VNA rig over and test it for real.

JJ

You posted just before I posted....solid dialectic (PE) and semi solid (PE tube with a PE string wrapped around the center conductor) are not as prone to bending shorts as expanded PE foam since they are mechanically more robust in regards to knifing.
Just some thoughts...

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

I can mostly speak as a long time manufacture of wire and cable. What type of dialectic does it have, the layer between the center conductor and the outer shielding? If foam (expanded PE), a sharp bend can cause the center conductor to knife through

the dialectic, causing a short. Issue is, you bend it one way, it's fine, change the angle of bend by 90*, it's shorted as the conductor moved around. Do a continuity check while bending the wire sharply every 90* in the last few inches, see if the
reading changes.

Charlie, thanks, I have been considering that very scenario. It does look like a low-loss foam center insulator (soft'ish) with a pretty stiff stranded center conductor. And... the cable was severely bent 90deg right at the connector. The only issue,
however, is that no amount of manipulation (including pulling some tension on the center conductor) has had any effect on the resistance readings. If I saw any variation, I'd cut off the end and test again. I'm just very hesitant to start hacking the
precious little length I have unless I'm more certain it will fix it.
thx, JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

You posted just before I posted....solid dialectic (PE) and semi solid (PE tube with a PE string wrapped around the center conductor) are not as prone to bending shorts as expanded PE foam since they are mechanically more robust in regards to knifing.
Just some thoughts...

Appreciate the insights. My cable appears to be very similar to this: https://www.ssb.de/de/koax1/koaxialkabel/7-mm
This cable supplier is 1 of 2 recommended in the TT22 installation manual.

Pocking at the end a bit, it deforms but doesn't readily split or tear. Definitely can't rule out your scenario.

JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 4:45:46 PM UTC-5, John Johnson wrote:

I can mostly speak as a long time manufacture of wire and cable. What type of dialectic does it have, the layer between the center conductor and the outer shielding? If foam (expanded PE), a sharp bend can cause the center conductor to knife through

the dialectic, causing a short. Issue is, you bend it one way, it's fine, change the angle of bend by 90*, it's shorted as the conductor moved around. Do a continuity check while bending the wire sharply every 90* in the last few inches, see if the
reading changes.

Charlie, thanks, I have been considering that very scenario. It does look like a low-loss foam center insulator (soft'ish) with a pretty stiff stranded center conductor. And... the cable was severely bent 90deg right at the connector. The only issue,

however, is that no amount of manipulation (including pulling some tension on the center conductor) has had any effect on the resistance readings. If I saw any variation, I'd cut off the end and test again. I'm just very hesitant to start hacking the
precious little length I have unless I'm more certain it will fix it.

thx, JJ

As I stated, if expanded foam, it can be good or fail on rotation....sorta trust me, been there, done that...a 1,000,000' worth...

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 4:54:11 PM UTC-5, John Johnson wrote:

You posted just before I posted....solid dialectic (PE) and semi solid (PE tube with a PE string wrapped around the center conductor) are not as prone to bending shorts as expanded PE foam since they are mechanically more robust in regards to knifing.
Just some thoughts...

Appreciate the insights. My cable appears to be very similar to this: https://www.ssb.de/de/koax1/koaxialkabel/7-mm
This cable supplier is 1 of 2 recommended in the TT22 installation manual.

Pocking at the end a bit, it deforms but doesn't readily split or tear. Definitely can't rule out your scenario.

JJ

You won't see it, a simple continuity test can confirm at certain bend angles...if in doubt, bite the bullet and cut before the sharp bend...or, run a new cable and leave a small service loop...

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 3:44:20 PM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:

On Tuesday, November 29, 2022 at 4:54:11 PM UTC-5, John Johnson wrote:

You posted just before I posted....solid dialectic (PE) and semi solid (PE tube with a PE string wrapped around the center conductor) are not as prone to bending shorts as expanded PE foam since they are mechanically more robust in regards to

knifing.

Just some thoughts...

Appreciate the insights. My cable appears to be very similar to this: https://www.ssb.de/de/koax1/koaxialkabel/7-mm
This cable supplier is 1 of 2 recommended in the TT22 installation manual.

Pocking at the end a bit, it deforms but doesn't readily split or tear. Definitely can't rule out your scenario.

JJ

You won't see it, a simple continuity test can confirm at certain bend angles...if in doubt, bite the bullet and cut before the sharp bend...or, run a new cable and leave a small service loop...

I was thinking about cutting off the end, re-applying the connector, and then adding a short service loop with a lower performance but more conformable cable connected to the radio.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 5:55:19 PM UTC-5, John Johnson wrote:

On Tuesday, November 29, 2022 at 3:44:20 PM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:

On Tuesday, November 29, 2022 at 4:54:11 PM UTC-5, John Johnson wrote:

You posted just before I posted....solid dialectic (PE) and semi solid (PE tube with a PE string wrapped around the center conductor) are not as prone to bending shorts as expanded PE foam since they are mechanically more robust in regards to

knifing.

Just some thoughts...

Appreciate the insights. My cable appears to be very similar to this: https://www.ssb.de/de/koax1/koaxialkabel/7-mm
This cable supplier is 1 of 2 recommended in the TT22 installation manual.

Pocking at the end a bit, it deforms but doesn't readily split or tear. Definitely can't rule out your scenario.

JJ

You won't see it, a simple continuity test can confirm at certain bend angles...if in doubt, bite the bullet and cut before the sharp bend...or, run a new cable and leave a small service loop...

I was thinking about cutting off the end, re-applying the connector, and then adding a short service loop with a lower performance but more conformable cable connected to the radio.

Try this tool
https://www.youtube.com/watch?v=9thbTC8-JtA

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Try this tool
https://www.youtube.com/watch?v=9thbTC8-JtA

Thanks John - I've been looking at this very same VNA. Looks like ~$50. My RF skills are so weak I may just end up confusing myself with a very capable tool (kind of like the situation flying my new glider). Still, at that price, its worth a shot.
Still hoping a local HAM responds to my facebook help request.

thx, JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tuesday, November 29, 2022 at 8:29:59 PM UTC-8, Stuart Venters wrote:

If it passed the last transponder check, it may be a good 50 ohm match
at 1090Mhz, even if it reads a short at dc.

A VNA to look at the antenna is sub $100 these days. (Search amazon for nanovna.) These also have a TDR display mode, but I've not tried it.
On 11/29/22 13:23, John Johnson wrote:

So, I've been trying to figure out why my radio range is poor relative to my peers on my new-to-me ASH 31 Mi. While messing with SWR measurements and such, I used a cheap signal locator tool (inserts a tone into the cable and a hand wand picks it up)

to find where the radio antenna was located in the fin. This worked well, so for the heck of it, I went to do the same for the transponder.

It didn't work at all. The tone was killed as soon I hooked up the tone generator's leads to the connector's center conductor and the barrel. So I put my ohm meter on the connector and found it appeared shorted center pin to barrel with very low

resistance (0.1ohm). What?? As far as I knew, the transponder was working fine and I saw good ADSB tracking history last I looked a few months ago.

Assuming my manipulation of the instrument panel and cables caused a short in the connector, I disassembled it. No luck, no stray shield braid wires getting to the center conductor. Manipulation of the cable end does not affect the short. I have

access to about 1.5ft of the ~25ft cable before it dives into the inaccessible fuselage structure. While I want to suspect the short is in the last inch or so (where I saw the cable being severely bent coming out of the connector), I don't have enough
spare length to just start guessing and cutting. I actually just joined a HAM radio facebook group to ask for help (someone who can VNA/TDR the cable and maybe narrow down the short location).

Anyone out there with advice or a similar experience? I'm a retired electrical / automation engineer but my RF experience is weak. Is there any chance this 'short' is correct? The Trig TT22 installation manual indicates this should be a simple 50ohm

system with a high quality cable going into a dipole or antenna with a ground plane.

Truly dismayed and a bit overwhelmed to find this surprise issue. I can't imagine the hassle a deeply located short would be.

JJ

I bought this VNA to troubleshoot a friend's radio antenna problem: https://www.amazon.com/gp/product/B07Z5VY7B6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
A transponder antenna is a monopole with a ground plane - there should be no continuity between the center conductor and the shield, so there is a short somewhere. Just because it worked recently means nothing - everything works until it breaks.

Tom

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

If it passed the last transponder check, it may be a good 50 ohm match
at 1090Mhz, even if it reads a short at dc.

A VNA to look at the antenna is sub $100 these days. (Search amazon for nanovna.) These also have a TDR display mode, but I've not tried it.






On 11/29/22 13:23, John Johnson wrote:

So, I've been trying to figure out why my radio range is poor relative to my peers on my new-to-me ASH 31 Mi. While messing with SWR measurements and such, I used a cheap signal locator tool (inserts a tone into the cable and a hand wand picks it up)

to find where the radio antenna was located in the fin. This worked well, so for the heck of it, I went to do the same for the transponder.

It didn't work at all. The tone was killed as soon I hooked up the tone generator's leads to the connector's center conductor and the barrel. So I put my ohm meter on the connector and found it appeared shorted center pin to barrel with very low

resistance (0.1ohm). What?? As far as I knew, the transponder was working fine and I saw good ADSB tracking history last I looked a few months ago.

Assuming my manipulation of the instrument panel and cables caused a short in the connector, I disassembled it. No luck, no stray shield braid wires getting to the center conductor. Manipulation of the cable end does not affect the short. I have

access to about 1.5ft of the ~25ft cable before it dives into the inaccessible fuselage structure. While I want to suspect the short is in the last inch or so (where I saw the cable being severely bent coming out of the connector), I don't have enough
spare length to just start guessing and cutting. I actually just joined a HAM radio facebook group to ask for help (someone who can VNA/TDR the cable and maybe narrow down the short location).

Anyone out there with advice or a similar experience? I'm a retired electrical / automation engineer but my RF experience is weak. Is there any chance this 'short' is correct? The Trig TT22 installation manual indicates this should be a simple 50ohm

system with a high quality cable going into a dipole or antenna with a ground plane.

Truly dismayed and a bit overwhelmed to find this surprise issue. I can't imagine the hassle a deeply located short would be.

JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

I've not ohmed an internal transponder antenna.

It might be different that just a simple monopole with a ground plane.


On 11/29/22 23:00, 2G wrote:

On Tuesday, November 29, 2022 at 8:29:59 PM UTC-8, Stuart Venters wrote:

If it passed the last transponder check, it may be a good 50 ohm match
at 1090Mhz, even if it reads a short at dc.

A VNA to look at the antenna is sub $100 these days. (Search amazon for
nanovna.) These also have a TDR display mode, but I've not tried it.
On 11/29/22 13:23, John Johnson wrote:

So, I've been trying to figure out why my radio range is poor relative to my peers on my new-to-me ASH 31 Mi. While messing with SWR measurements and such, I used a cheap signal locator tool (inserts a tone into the cable and a hand wand picks it up)

to find where the radio antenna was located in the fin. This worked well, so for the heck of it, I went to do the same for the transponder.

It didn't work at all. The tone was killed as soon I hooked up the tone generator's leads to the connector's center conductor and the barrel. So I put my ohm meter on the connector and found it appeared shorted center pin to barrel with very low

resistance (0.1ohm). What?? As far as I knew, the transponder was working fine and I saw good ADSB tracking history last I looked a few months ago.

Assuming my manipulation of the instrument panel and cables caused a short in the connector, I disassembled it. No luck, no stray shield braid wires getting to the center conductor. Manipulation of the cable end does not affect the short. I have

access to about 1.5ft of the ~25ft cable before it dives into the inaccessible fuselage structure. While I want to suspect the short is in the last inch or so (where I saw the cable being severely bent coming out of the connector), I don't have enough
spare length to just start guessing and cutting. I actually just joined a HAM radio facebook group to ask for help (someone who can VNA/TDR the cable and maybe narrow down the short location).

Anyone out there with advice or a similar experience? I'm a retired electrical / automation engineer but my RF experience is weak. Is there any chance this 'short' is correct? The Trig TT22 installation manual indicates this should be a simple 50ohm

system with a high quality cable going into a dipole or antenna with a ground plane.

Truly dismayed and a bit overwhelmed to find this surprise issue. I can't imagine the hassle a deeply located short would be.

JJ

I bought this VNA to troubleshoot a friend's radio antenna problem: https://www.amazon.com/gp/product/B07Z5VY7B6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
A transponder antenna is a monopole with a ground plane - there should be no continuity between the center conductor and the shield, so there is a short somewhere. Just because it worked recently means nothing - everything works until it breaks.

Tom

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

It's quite possible that it works even though it appears shorted. I found a similar issue not long ago with a VHF antenna. Antenna showed a short on the multimeter, but when I used a high end digital SW meter, the result was good and it was
transmitting and receiving quite well. I left it alone.

The device 2G posted appears to have the frequency range > ~1100Mhz or 1.1 GHz (as opposed to 1.21 Gigawatts) to check the transponder antenna and cable, but you will probably need an adapter from their cable to the TNC connections on your system if it's
Trig.

https://www.amazon.com/gp/product/B07Z5VY7B6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

For ~$60 it's a pretty cheap test and you may find it's fine.

If you can pull a recent PAPR report, maybe just accept that it's fine until you're sure it's not and save yourself the $60 plus cost of the adapters.

https://adsbperformance.faa.gov/PAPRRequest.aspx

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

If you can pull a recent PAPR report, maybe just accept that it's fine until you're sure it's not and save yourself the $60 plus cost of the adapters.

https://adsbperformance.faa.gov/PAPRRequest.aspx

The reports were good including my last flight 10/29. But I have been working on my panel since then and, perhaps, the cable kink at the connector did exactly as Charlie suspects and shorted out there as I was moving things around. I had no suspicions
of any xpndr problem and just sort of casually put my ohmmeter on it while my actual focus was on radio issues. Now I'm not comfortable turning on the transponder with the potential for this to be an actual short circuit. Hopefully this is just a case
of creating a phantom problem (and stress) for myself.
I ordered the VNA from Amazon - should arrive today. Assuming I can get through the youtube tutorials and operate it correctly, I'll report my findings. (did I mention I really hate house plumbing and RF issues?)
JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Still hoping a local HAM responds to my facebook help request.

thx, JJ

You might have a local HAM club. Look here: https://www.arrl.org/find-a-club
I am sure someone will be happy to come help you, complete with all the test equipment.
Todd "N8RNW"

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

JJ,

Some sort of related things come to mind.

Can you disconnect the cable at the antenna (BNC) connector? If so then test continuity again at the transponder (TNC) connector? Maybe not as you say your transponder antenna is in the fin and I have no idea where that might be in an ASH-31 (ask AS

or Rex?). My ASW-27 transponder antenna is also in the fit but near the top in the battery box. As the radio (transceiver) antenna is at the leading edge of the fin I would think that putting another strong transmitter antenna along the leading edge
would not be wise (but what do I know - I am a "bit pusher" EE).

As I launch just outside the 30nm veil of ORD I could have a terrible antenna or coax and still the FAA would give me the thumbs up. Thus this may give you a false positive.

A sharp bend in coax can cause a significant change in the impedance. A VNA can help spot this - not an ohm meter. This can reflect some/most/all your transponder's transmission right back into the transponder. If this is the case for you then your

transponder will pull more amps from your battery causing a voltage droop which you can watch for. I would guess that 0.5Vdc is OK while 1.0Vdc is something to worry about. I spotted a bad transceiver BNC connector this way. Lots of variables to this
guessing game. It is best to have a baseline voltage droop of a properly working system to compare against (each electronic device one at a time).

If you purchase a VNA also purchase the following;

- As these simple VNAs seem to always have SMA connectors you will need some BNC to SMA and TNC to SMA adapters. Buy every combination of sexes and several of each type. Ninety degree adapters are also handy in tight places.
- Purchase BNC and TNC cable extenders - male at one end and female at the other. Handy in tight quarters. About 2 feet is usually all you will need.

The Ham guys may, or may not, be able to help as the frequencies they typically use could be a parsec away from our aircraft frequencies.

Man, I hate radio problems.

Best of Luck.

- John (OHM)
aviation.derosaweb.net/presentations/#radio

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Thursday, December 1, 2022 at 10:17:54 AM UTC-7, Dan Marotta wrote:

... Or maybe get a transponder check done. The cost may be less than
buying all of those parts and you get a logbook entry.

Got ADS-B? Turn it on have someone similarly equipped, or with Flarm
see if he sees you.

Dan
5J

Dan - I'm so tempted but if its actually shorted, I'm worried about damaging the transponder.

JJ

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

... Or maybe get a transponder check done. The cost may be less than
buying all of those parts and you get a logbook entry.

Got ADS-B? Turn it on have someone similarly equipped, or with Flarm
see if he sees you.

Dan
5J

On 11/30/22 22:40, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

JJ,

Some sort of related things come to mind.

Can you disconnect the cable at the antenna (BNC) connector? If so then test continuity again at the transponder (TNC) connector? Maybe not as you say your transponder antenna is in the fin and I have no idea where that might be in an ASH-31 (ask AS

or Rex?). My ASW-27 transponder antenna is also in the fit but near the top in the battery box. As the radio (transceiver) antenna is at the leading edge of the fin I would think that putting another strong transmitter antenna along the leading edge
would not be wise (but what do I know - I am a "bit pusher" EE).

As I launch just outside the 30nm veil of ORD I could have a terrible antenna or coax and still the FAA would give me the thumbs up. Thus this may give you a false positive.

A sharp bend in coax can cause a significant change in the impedance. A VNA can help spot this - not an ohm meter. This can reflect some/most/all your transponder's transmission right back into the transponder. If this is the case for you then your

transponder will pull more amps from your battery causing a voltage droop which you can watch for. I would guess that 0.5Vdc is OK while 1.0Vdc is something to worry about. I spotted a bad transceiver BNC connector this way. Lots of variables to this
guessing game. It is best to have a baseline voltage droop of a properly working system to compare against (each electronic device one at a time).

If you purchase a VNA also purchase the following;

- As these simple VNAs seem to always have SMA connectors you will need some BNC to SMA and TNC to SMA adapters. Buy every combination of sexes and several of each type. Ninety degree adapters are also handy in tight places.
- Purchase BNC and TNC cable extenders - male at one end and female at the other. Handy in tight quarters. About 2 feet is usually all you will need.

The Ham guys may, or may not, be able to help as the frequencies they typically use could be a parsec away from our aircraft frequencies.

Man, I hate radio problems.

Best of Luck.

- John (OHM)
aviation.derosaweb.net/presentations/#radio

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On Wednesday, November 30, 2022 at 10:40:32 PM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

JJ,

Some sort of related things come to mind.

Can you disconnect the cable at the antenna (BNC) connector? If so then test continuity again at the transponder (TNC) connector? Maybe not as you say your transponder antenna is in the fin and I have no idea where that might be in an ASH-31 (ask AS

or Rex?). My ASW-27 transponder antenna is also in the fit but near the top in the battery box. As the radio (transceiver) antenna is at the leading edge of the fin I would think that putting another strong transmitter antenna along the leading edge
would not be wise (but what do I know - I am a "bit pusher" EE).

As I launch just outside the 30nm veil of ORD I could have a terrible antenna or coax and still the FAA would give me the thumbs up. Thus this may give you a false positive.

A sharp bend in coax can cause a significant change in the impedance. A VNA can help spot this - not an ohm meter. This can reflect some/most/all your transponder's transmission right back into the transponder. If this is the case for you then your

transponder will pull more amps from your battery causing a voltage droop which you can watch for. I would guess that 0.5Vdc is OK while 1.0Vdc is something to worry about. I spotted a bad transceiver BNC connector this way. Lots of variables to this
guessing game. It is best to have a baseline voltage droop of a properly working system to compare against (each electronic device one at a time).

If you purchase a VNA also purchase the following;

- As these simple VNAs seem to always have SMA connectors you will need some BNC to SMA and TNC to SMA adapters. Buy every combination of sexes and several of each type. Ninety degree adapters are also handy in tight places.
- Purchase BNC and TNC cable extenders - male at one end and female at the other. Handy in tight quarters. About 2 feet is usually all you will need.

The Ham guys may, or may not, be able to help as the frequencies they typically use could be a parsec away from our aircraft frequencies.

Man, I hate radio problems.

Best of Luck.

- John (OHM)
aviation.derosaweb.net/presentations/#radio

Thanks John, appreciate the advice - I'm a 'RF-hating bit pusher EE' too.

So I have a cheap cable finder (beeper) that tells me the radio's antenna is placed inside the fin at the back about mid-height. The xpndr's antenna looks like it is at the front of the fin just below the TE probe. Neither have any access that I've
been able to find but I haven't pulled the rudder. It's been difficult to come to terms with how inaccessible glider components are. Frankly, I think a lot of this is simply lazy design practice. Much of my career was focused on architecting
manufacturing equipment. MTBF and MTTR were critical for cost effective operation and full maintenance access was always a critical design constraint. I do concede that structural composite shells are pretty challenging to populate with access holes.

My good xpndr reports include 500km XC flights reaching >100km distance from PHX and TUC so I think it's been working fine (if you're interested, look on the adsb exchange website for 10/1/22, filter for N311MP at ~21:30 zulu). I like papr reports and
adsb exchange tracker for the overall system assessment. I find that other pilot's reports are often confounded between FLARM vs ADSB (and their various system's variable reception performance for those 2 bands).

The sharp kink in the cable at the connector definitely has me worried and I'll take Charlie's advice and cut that off once I have a testing baseline. I'm actually re-mounting all of the behind-the-panel instruments to prevent that issue.

I now have in hand the nanovna, a slew of adapters, and a pot of coffee. Once I hit 'send' on this note, I'm firing up youtube tutorials and will start getting dangerous.
thx, JJ

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Maybe an email to Trig will help. I found them extremely helpful when I
was installing my first TT22 years back.

Dan
5J

On 12/1/22 10:38, John Johnson wrote:

On Thursday, December 1, 2022 at 10:17:54 AM UTC-7, Dan Marotta wrote:

... Or maybe get a transponder check done. The cost may be less than
buying all of those parts and you get a logbook entry.

Got ADS-B? Turn it on have someone similarly equipped, or with Flarm
see if he sees you.

Dan
5J

Dan - I'm so tempted but if its actually shorted, I'm worried about damaging the transponder.

JJ

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Ok - after a lot of coffee and too many youtube tutorials, I worked up my courage and attached the NanoVNA to the antenna cable.

Conclusions:
1) The NanoVNA is a pretty awesome tool. Very powerful and even a rook like me can extract meaningful results. I'd be even more impressed if knew enough about RF to extract the other 90% of its capability. I highly recommend it to anyone doing basic
avionic work on their gliders. Just $65 total after tax from Amazon.
2) "Nevermind" The insertion loss, impedance, and SWR (and other cable/antenna characteristics I sort of understand) looked great at 1090MHz. I can safely say the xpndr antenna is good to go. YAY!!!
3) My VHF radio antenna is 'ok'. I was happy to see the SWR at 123.5MHz drop from 2.1 to 1.6 as I swung the glider's tail away from my trailer. Apparently a nearby big metal structure affects the antenna's characteristics during measurements. Since
my tail is sandwiched between my trailer and truck in the garage, I'll need to do some open air testing later.

For now a very relieved JJ is switching to beer. Tune into my next glider drama - they usually hit every 4-5 weeks.

JJ

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I did exchange friendly emails with Trig but they basically said there are many different antenna types that work with their transponders.

On Thursday, December 1, 2022 at 4:52:36 PM UTC-7, Dan Marotta wrote:

Maybe an email to Trig will help. I found them extremely helpful when I
was installing my first TT22 years back.

Dan

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On Thursday, December 1, 2022 at 8:12:50 PM UTC-5, John Johnson wrote:

Ok - after a lot of coffee and too many youtube tutorials, I worked up my courage and attached the NanoVNA to the antenna cable.

Conclusions:
1) The NanoVNA is a pretty awesome tool. Very powerful and even a rook like me can extract meaningful results. I'd be even more impressed if knew enough about RF to extract the other 90% of its capability. I highly recommend it to anyone doing basic

avionic work on their gliders. Just $65 total after tax from Amazon.

2) "Nevermind" The insertion loss, impedance, and SWR (and other cable/antenna characteristics I sort of understand) looked great at 1090MHz. I can safely say the xpndr antenna is good to go. YAY!!!
3) My VHF radio antenna is 'ok'. I was happy to see the SWR at 123.5MHz drop from 2.1 to 1.6 as I swung the glider's tail away from my trailer. Apparently a nearby big metal structure affects the antenna's characteristics during measurements. Since my

tail is sandwiched between my trailer and truck in the garage, I'll need to do some open air testing later.

For now a very relieved JJ is switching to beer. Tune into my next glider drama - they usually hit every 4-5 weeks.

JJ

Was this after redoing the cable end?

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On Thursday, December 1, 2022 at 6:31:03 PM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:

On Thursday, December 1, 2022 at 8:12:50 PM UTC-5, John Johnson wrote:

Ok - after a lot of coffee and too many youtube tutorials, I worked up my courage and attached the NanoVNA to the antenna cable.

Conclusions:
1) The NanoVNA is a pretty awesome tool. Very powerful and even a rook like me can extract meaningful results. I'd be even more impressed if knew enough about RF to extract the other 90% of its capability. I highly recommend it to anyone doing basic

avionic work on their gliders. Just $65 total after tax from Amazon.

2) "Nevermind" The insertion loss, impedance, and SWR (and other cable/antenna characteristics I sort of understand) looked great at 1090MHz. I can safely say the xpndr antenna is good to go. YAY!!!
3) My VHF radio antenna is 'ok'. I was happy to see the SWR at 123.5MHz drop from 2.1 to 1.6 as I swung the glider's tail away from my trailer. Apparently a nearby big metal structure affects the antenna's characteristics during measurements. Since

my tail is sandwiched between my trailer and truck in the garage, I'll need to do some open air testing later.

For now a very relieved JJ is switching to beer. Tune into my next glider drama - they usually hit every 4-5 weeks.

JJ

Was this after redoing the cable end?

Hey Charlie, For now, I put the connector back on exactly as it came off the cable. I could see that the real time measurements and smith chart trace didn't change even with intense manipulation of the cable end. Regardless, I will be cutting off that
kinked portion and redoing the connector. I just wanted to get a baseline first before making that change.

JJ

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On 12/1/2022 5:12 PM, John Johnson wrote:

Ok - after a lot of coffee and too many youtube tutorials, I worked up my courage and attached the NanoVNA to the antenna cable.

Conclusions:
1) The NanoVNA is a pretty awesome tool. Very powerful and even a rook like me can extract meaningful results. I'd be even more impressed if knew enough about RF to extract the other 90% of its capability. I highly recommend it to anyone doing

basic avionic work on their gliders. Just $65 total after tax from Amazon.

2) "Nevermind" The insertion loss, impedance, and SWR (and other cable/antenna characteristics I sort of understand) looked great at 1090MHz. I can safely say the xpndr antenna is good to go. YAY!!!
3) My VHF radio antenna is 'ok'. I was happy to see the SWR at 123.5MHz drop from 2.1 to 1.6 as I swung the glider's tail away from my trailer. Apparently a nearby big metal structure affects the antenna's characteristics during measurements.

Since my tail is sandwiched between my trailer and truck in the garage, I'll need to do some open air testing later.

For now a very relieved JJ is switching to beer. Tune into my next glider drama - they usually hit every 4-5 weeks.

JJ

Even 1.6 is good performance, as that's about a 5% power loss, or less than 2.5% range loss.

https://n6pet.com/power-loss-various-swr/
--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications

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JJ,

Good to hear that you have climbed off the ledge.

One thought from one bit-pusher to another. Might putting a right angle TNC adapter help prevent a sharp coax bend? The answer may be no.

Rerouting the cabling to prevent the bending in the first place, rather than adding a right angle adapter, would seem to be preferred. But I was told way-back-when that adding a connector causes signal loss.

Then I found a video from an radio control airplane pilot experimenting with a VNA inserting (SMA) adapters and when bending coax. The author shows that adding a right angle connector looses 2db. Ouch! HOWEVER, he also shows that severely bending the
coax had a very low loss effect. Go figure.

See https://www.youtube.com/watch?v=-uw5HNfkFVI. NOTE that the frequencies he was experimenting with are 50X higher than what we use in "full scale" aviation.

- John (OHM)

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On Thursday, December 1, 2022 at 8:45:59 PM UTC-8, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

JJ,

Good to hear that you have climbed off the ledge.

One thought from one bit-pusher to another. Might putting a right angle TNC adapter help prevent a sharp coax bend? The answer may be no.

Rerouting the cabling to prevent the bending in the first place, rather than adding a right angle adapter, would seem to be preferred. But I was told way-back-when that adding a connector causes signal loss.

Then I found a video from an radio control airplane pilot experimenting with a VNA inserting (SMA) adapters and when bending coax. The author shows that adding a right angle connector looses 2db. Ouch! HOWEVER, he also shows that severely bending the

coax had a very low loss effect. Go figure.

See https://www.youtube.com/watch?v=-uw5HNfkFVI. NOTE that the frequencies he was experimenting with are 50X higher than what we use in "full scale" aviation.

- John (OHM)

If there is room, you could do a 270 degree loop. If there isn't room a right angle connector is the next best choice.

Tom

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Yup.

It's been a bit over 50 years since I got my BSEE degree, but I do
remember that.

Dan
5J

On 12/1/22 18:12, John Johnson wrote:

Apparently a nearby big metal structure affects the antenna's characteristics during measurements.

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On Thursday, December 1, 2022 at 11:23:03 PM UTC-7, 2G wrote:

On Thursday, December 1, 2022 at 8:45:59 PM UTC-8, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

JJ,

Good to hear that you have climbed off the ledge.

One thought from one bit-pusher to another. Might putting a right angle TNC adapter help prevent a sharp coax bend? The answer may be no.

Rerouting the cabling to prevent the bending in the first place, rather than adding a right angle adapter, would seem to be preferred. But I was told way-back-when that adding a connector causes signal loss.

Then I found a video from an radio control airplane pilot experimenting with a VNA inserting (SMA) adapters and when bending coax. The author shows that adding a right angle connector looses 2db. Ouch! HOWEVER, he also shows that severely bending the

coax had a very low loss effect. Go figure.

See https://www.youtube.com/watch?v=-uw5HNfkFVI. NOTE that the frequencies he was experimenting with are 50X higher than what we use in "full scale" aviation.

- John (OHM)

If there is room, you could do a 270 degree loop. If there isn't room a right angle connector is the next best choice.

Tom

Tom, John,
I did add a 90deg adapter to the list of doo-dads I picked up off of Amazon. I'm in the middle of redesigning the interior of the instrument pod layout (remote radio & xpndr, TN-72 ADSB out, solar charger, flask, fuses, wiring, tubing, local antennas,
etc) to clean everything up. I hope to avoid needing a 90deg adapter with the new layout. I was going to just replace the existing straight TNC cable connector with a 90deg version but, for this size cable, they are expensive and I haven't found one
that screws together and is removable like I prefer. I'll use the adapter if I have to.
JJ

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On Friday, December 2, 2022 at 2:39:53 PM UTC-6, Dan Marotta wrote:

Yup.

It's been a bit over 50 years since I got my BSEE degree, but I do
remember that.

Dan
5J
On 12/1/22 18:12, John Johnson wrote:

Apparently a nearby big metal structure affects the antenna's characteristics during measurements.

I think that every gliderport needs a Faraday Cage just for this type of issue. https://en.wikipedia.org/wiki/Faraday_cage

All in favor of the SSA providing a grant for this program please raise an aileron.

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On Friday, December 2, 2022 at 4:44:22 PM UTC-5, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:

On Friday, December 2, 2022 at 2:39:53 PM UTC-6, Dan Marotta wrote:

Yup.

It's been a bit over 50 years since I got my BSEE degree, but I do remember that.

Dan
5J
On 12/1/22 18:12, John Johnson wrote:

Apparently a nearby big metal structure affects the antenna's characteristics during measurements.

I think that every gliderport needs a Faraday Cage just for this type of issue. https://en.wikipedia.org/wiki/Faraday_cage

All in favor of the SSA providing a grant for this program please raise an aileron.

I hate screw on coax connectors. Nothing beats a proper crimp (especially the crimp in your wallet for the proper crimp tools and dies).

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Just wait until you mangle the GPS coax to an Air Avionics ISU. Itty-bitty cable with itty-bitty connector needing another expensive crimp tool or a ham radio buddy.

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