Transponder check

I just took my Pegasus in to have the Trig T21 checked. The glider is relatively new to me and this is the first time I've personally taken it for the test. My former partner took it to the same shop two years ago and it passed and without comment from the tester, as far as I know. The guy doing the testing said that the power output was low - getting 35 watts while the glider was in the cradle, 65 watts at some point after we backed it off and some other, higher, reading a bit later after jockeying the test antenna around a bit. I don't know what that figure was. The antenna in the glider is a flat type that is mounted on the belly under the seat pan. The connection looked good but he cleaned it anyway. Its to the right of center line and the testing was done from the left, if that matters. He tried using his own antenna and didn't see any improvement. He did a fair amount of button pushing equipment moving and finally said, "I got it to pass but in the off season send it out to get checked." He also mentioned that the frequencies were a bit off.

I got the impression that he wasn't that familiar with the Trig unit or gliders. So, what kind output should I be seeing 4' from the glider? What could be causing the low output? The battery was almost, if not completely, fully charged. Why would the frequencies drift?

On Sunday, June 9, 2019 at 8:43:42 AM UTC-4, wrote:
I just took my Pegasus in to have the Trig T21 checked. The glider is relatively new to me and this is the first time I've personally taken it for the test. My former partner took it to the same shop two years ago and it passed and without comment from the tester, as far as I know. The guy doing the testing said that the power output was low - getting 35 watts while the glider was in the cradle, 65 watts at some point after we backed it off and some other, higher, reading a bit later after jockeying the test antenna around a bit. I don't know what that figure was. The antenna in the glider is a flat type that is mounted on the belly under the seat pan. The connection looked good but he cleaned it anyway. Its to the right of center line and the testing was done from the left, if that matters. He tried using his own antenna and didn't see any improvement. He did a fair amount of button pushing equipment moving and finally said, "I got it to pass but in the off season send it out to get checked." He also mentioned that the frequencies were a bit off.

I got the impression that he wasn't that familiar with the Trig unit or gliders. So, what kind output should I be seeing 4' from the glider? What could be causing the low output? The battery was almost, if not completely, fully charged. Why would the frequencies drift?

Is your transponder firmware up to date? https://trig-avionics.com/support/tr...duct-software/ "The current version of software installed in your Trig product will be shown on the display at initial power up." Version 2.13 is current.

I wouldn't want the antenna under my seat pan...

Yesterday the company I work for had a problem with many aircraft (hundreds) that had ADSB recently installed. There was an unusual amount of solar activity that knocked out the ADSB and as a consequence the transponder too. I dont know the details but it was only a problem for one aircraft type in the fleet. My point here is that in some equipment/instalation combinations solar activity will effect reliability of these systems.

On Sunday, June 9, 2019 at 6:56:53 AM UTC-7, wrote:
Yesterday the company I work for had a problem with many aircraft (hundreds) that had ADSB recently installed. There was an unusual amount of solar activity that knocked out the ADSB and as a consequence the transponder too.. I dont know the details but it was only a problem for one aircraft type in the fleet. My point here is that in some equipment/instalation combinations solar activity will effect reliability of these systems.

It will be interesting to understand what is going on there, multiple reports on twitter and elsewhere of CRJ and some Boeing aircraft having issues.

It should take a very large solar flare to affect GPS reception. With a few quick searches I don’t see reports of large solar flares or geomagnetic storms. Where is John Leibacher when you need him? :-)

An ADS-B GPS receiver problem should not ever “knock-out� a transponder. It may prevent the transponder transmitting ADS-B position data, but the device should keep working as a transponder. If it is then... wholly ASB and AD Batman.

I am curious if all those aircraft have Rockwell Collins receivers like GLU-925/GLU-2100 series?

On Sunday, June 9, 2019 at 10:16:44 AM UTC-7, Darryl Ramm wrote:
On Sunday, June 9, 2019 at 6:56:53 AM UTC-7, wrote:
Yesterday the company I work for had a problem with many aircraft (hundreds) that had ADSB recently installed. There was an unusual amount of solar activity that knocked out the ADSB and as a consequence the transponder too. I dont know the details but it was only a problem for one aircraft type in the fleet. My point here is that in some equipment/instalation combinations solar activity will effect reliability of these systems.

It will be interesting to understand what is going on there, multiple reports on twitter and elsewhere of CRJ and some Boeing aircraft having issues..

It should take a very large solar flare to affect GPS reception. With a few quick searches I don’t see reports of large solar flares or geomagnetic storms. Where is John Leibacher when you need him? :-)

An ADS-B GPS receiver problem should not ever “knock-out� a transponder. It may prevent the transponder transmitting ADS-B position data, but the device should keep working as a transponder. If it is then... wholly ASB and AD Batman.

I am curious if all those aircraft have Rockwell Collins receivers like GLU-925/GLU-2100 series?

....and the FAA is officially fingering Rockwell Collins. I'll wager good money this is nothing to do with solar activity, and wager less money that somebody gooched some software... the same company that cannot get GPS epoch rollover done properly.

https://www.fly.faa.gov/adv/adv_othe...eDate=06/09/19

On Sunday, June 9, 2019 at 1:16:44 PM UTC-4, Darryl Ramm wrote:
Where is John Leibacher when you need him? :-)

Paris, at least a few weeks ago last I heard from him,
still GONGing I presume...
And he *still* makes time to keep up databases for everyone,
Thanks John!

On Sunday, June 9, 2019 at 5:43:42 AM UTC-7, wrote:
I got the impression that he wasn't that familiar with the Trig unit or gliders. So, what kind output should I be seeing 4' from the glider? What could be causing the low output? The battery was almost, if not completely, fully charged. Why would the frequencies drift?

Why are you asking r.a.s. these questions?... the test technician was right there testing your transponder. Ask him. Especially ask him exactly what he did to get it to pass.

I also would not be sitting on a transponder antenna. You are also a sack of water that may affect/obstruct some of the signal. I would get the antenna back in the tail boom. Away from metal structures. An external 1/4 wave antenna with ground plane may be better.

The RF output that should be seen is at least what is specified in the transponder RF test in 14 CFR Part 43 Appendix F. But it’s aiming at seeing 70W for a nominal 125W or 125W for a nominal 250W transponder. So what is you transponder a TT21 or TT22? But either way, the initial power measurements you mention are a clear fail.

Trig transponders rely on the use of low-loss cabling and proper antenna installation. The Trig install documentation is well written and very clear about what is needed. With any transponder cabling and antenna are suspect any time the power is too low. I would hope a technician connects direct to the coax or transponder RF output connector and checks that if in doubt.

Why do frequencies drift? Why do they not (well strictly they always are)? It’s all the magic power of crystals. Frequency reference crystals sometimes age badly, might not like the transponder being dropped or vibrated around in a trailer, or the electronics that drive the phase lock loop/frequency multipliers goes wonky... but I would not rely on one test with one technician with one test set. Have it rechecked by somebody else and/or just get it to Midcontibent for them to check out.