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Radio range issues

Jesse

Well Known Member
We are having a problem that I wanted to post here to see if anybody here has a valuable suggestion. In a new RV-10 with a professional audio harness (Approach Fast Stack), we are having problem with receive range on our radios. We have a GMA245 audio panel, a Dynon Com (Trig Transceiver) and a GTN650. This has been an ongoing problem that didn't appear at first, but became noticeable around 10-15 hours from new.

On a test the other day, the plane left here. From our base station radio with an antenna on the top of the hangar, we had great reception for the first couple of miles. The further he got away, the more weak and staticy the plane received, although the transmit was still loud and clear. When the plane was 15 miles away, he could not receive the base station at all, and he was still loud and clear receiving at the base station. In summary, his receive range is very short, but transmit seems to be good, or at least better. This problem is with both radios.

We have verified that we have good coax from both radios. to their respective antennas, which are the RAMI AV-17's, and the coax run down opposite sides of the plane to their respective antennas. Both antennas were new when installed and bought together. We removed some paint where the screws attach the antenna to the airplane, and used lock washers under the nuts after removing primer from where the nuts tighten down, so we know we have a good ground (the antennas are under the pilot and copilot seats). We have tested with each radio powered down and the problem is still with the powered radio, so it isn't cross-talk. We have verified, and added, a good ground from the audio panel to the airframe. We have tried with both pilot and copilot headset alone, with an without the rear headsets, and have tried other known good headsets. We have replaced the Dynon transceiver 2 or 3 times, thinking it was specific to that radio, with no change. The intercom works just fine all the way around. We have swapped with another GMA245 audio panel and there was no change, so it's not a bad audio panel.

The only thing we can think of that is left to check is to replace one or both of the COM antennas. I have never had a bad RAMI bent whip antenna, certainly not out of the box, and the likelihood of two at the same time on the same plane seems even more unlikely, unless they were both from the same batch that happened to be a bad batch, but I don't know how we would change that.

As a side note, this plane has the full EFII system with the buss manager. We are going to test reception range on the ground with the engine on and off soon to see if the engine could be causing any disruption.

Any thoughts?
 
Considering you state that both radios have the same problem, I suggest both antennas and/or feed lines failing at the same time in the same way is not a high probability. Here however a few minutes with a real antenna analyzer to ring out the system would quickly confirm this assumption.

If the antenna, feed lines and fittings are good, then look at the radios - or more specifically a common fault that will degrade receiver sensitivity on both radios.

So:
- Did you eliminate RF noise makers (USB chargers, led Nav/Strobes, led landing lights and such) to verify the problem still present?
- Did you change anything, like connecting the Garmin “receiver de-sensation” line on the GTN-650?
- Did you try bypassing the audio panel (turning it off) so you have a direct connection between the headset and radio?

Side note - scraping paint on an antenna mount is not required or desired. Using star washers on the inside is more than adequate.

Carl
 
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Have you completed your testing with another base station or aircraft? Could be a problem with your base station.
 
Have you completed your testing with another base station or aircraft? Could be a problem with your base station.

We did the specific testing with the base station because he was seeing the problem in flight. It is not a base station problem.
 
Considering you state that both radios have the same problem, I suggest both antennas and/or feed lines failing at the same time in the same way is not a high probability. Here however a few minutes with a real antenna analyzer to ring out the system would quickly confirm this assumption.

If the antenna, feed lines and fittings are good, then look at the radios - or more specifically a common fault that will degrade receiver sensitivity on both radios.

So:
- Did you eliminate RF noise makers (USB chargers, led Nav/Strobes, led landing lights and such) to verify the problem still present?
- Did you change anything, like connecting the Garmin “receiver de-sensation” line on the GTN-650?
- Did you try bypassing the audio panel (turning it off) so you have a direct connection between the headset and radio?

Side note - scraping paint on an antenna mount is not required or desired. Using star washers on the inside is more than adequate.

Carl
We have turned on and off just about all things that could be turned off, although possibly not the USB chargers, which we have never had a problem with. We will try that.
We did not change anything, but there could be a setting to change that. I have a hard time seeing how we could have the same problem with both radios if it were something like that.
We have not tried turning off the audio panel. We tried a different audio panel, but that is a good thought.

Thanks.
 
We have turned on and off just about all things that could be turned off, although possibly not the USB chargers, which we have never had a problem with. We will try that.
We did not change anything, but there could be a setting to change that. I have a hard time seeing how we could have the same problem with both radios if it were something like that.
We have not tried turning off the audio panel. We tried a different audio panel, but that is a good thought.

Thanks.
+1 on receiver sensitivity being affected as a possibility.

Another easy thing to try is:
(Forgive me if you have already done all of this. Just throwing out ideas),

1. Push the plane into the metal hangar and close the doors.
2. Tune in ATIS. If it is very strong try a station that is weaker. One that you can barely receive.
3. Turn everything on and one by one, everything off, and see if you detect any difference. Being on the ground without engine noise may help locate the problem.

An alternative is to have the plane outside and dial in the weakest ATIS you can find. Repeat above but with the engine (EI) running and not running.

Totally different matter ... is there any oil on the antenna>>
 
Reception Range

We are having a problem that I wanted to post here to see if anybody here has a valuable suggestion. In a new RV-10 with a professional audio harness (Approach Fast Stack), we are having problem with receive range on our radios. We have a GMA245 audio panel, a Dynon Com (Trig Transceiver) and a GTN650. This has been an ongoing problem that didn't appear at first, but became noticeable around 10-15 hours from new.

On a test the other day, the plane left here. From our base station radio with an antenna on the top of the hangar, we had great reception for the first couple of miles. The further he got away, the more weak and staticy the plane received, although the transmit was still loud and clear. When the plane was 15 miles away, he could not receive the base station at all, and he was still loud and clear receiving at the base station. In summary, his receive range is very short, but transmit seems to be good, or at least better. This problem is with both radios.



We have verified that we have good coax from both radios. to their respective antennas, which are the RAMI AV-17's, and the coax run down opposite sides of the plane to their respective antennas. Both antennas were new when installed and bought together. We removed some paint where the screws attach the antenna to the airplane, and used lock washers under the nuts after removing primer from where the nuts tighten down, so we know we have a good ground (the antennas are under the pilot and copilot seats). We have tested with each radio powered down and the problem is still with the powered radio, so it isn't cross-talk. We have verified, and added, a good ground from the audio panel to the airframe. We have tried with both pilot and copilot headset alone, with an without the rear headsets, and have tried other known good headsets. We have replaced the Dynon transceiver 2 or 3 times, thinking it was specific to that radio, with no change. The intercom works just fine all the way around. We have swapped with another GMA245 audio panel and there was no change, so it's not a bad audio panel.

The only thing we can think of that is left to check is to replace one or both of the COM antennas. I have never had a bad RAMI bent whip antenna, certainly not out of the box, and the likelihood of two at the same time on the same plane seems even more unlikely, unless they were both from the same batch that happened to be a bad batch, but I don't know how we would change that.

As a side note, this plane has the full EFII system with the buss manager. We are going to test reception range on the ground with the engine on and off soon to see if the engine could be causing any disruption.

Any thoughts?


Can't remember on the GTN 650, but when I recently upgraded to the 650 Xi, I started to have a receive problem with the Xi. In the configuration settings, go to the COM page and make sure the Squelch setting is lowered to 10 percent or less. I was having problems with hearing range till I lowered the default setting. What's weird about yours is that it's on 2 radios (I'm ignorant about the Dynon setup).
 
I'm missing something........

We did the specific testing with the base station because he was seeing the problem in flight. It is not a base station problem.

Not quite sure I understand this logic. If the base station has a weak transmitter or high VSWR on the antenna it would create this scenario.

Does the aircraft receive weak signals from other aircraft and/or other ground stations?

Do other aircraft receive strong signal from your base station?
 
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Not quite sure I understand this logic. If the base station has a weak transmitter or high VSWR it would create this scenario.

Does the aircraft receive weak signals from other aircraft and/or other ground stations?

Do other aircraft receive strong signal from your base station?

+1

I would go 30 miles from the base station with a different plane and see if it receives from the base station.

Larry
 
I good tool I use for checking antennas is a NanoVNA which one can get on Amazon for $60.

Here I am sweeping the entire band checking one of Don Pansier's excellent antennas. The cursor is showing SWR at 1.52 at around 122.900mhz.

There could be some bad crimps of the BNC connectors so I would also check at the radio end.
 

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If the base station has a weak transmitter or high VSWR on the antenna it would create this scenario.
Exactly, a high VSWR on the base station would create this exact scenario. Don't ask me how I know. :rolleyes:
Do other aircraft receive strong signal from your base station?
This is a great way to check if the problem is with your base station, which it appears to be. :cool:
 
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Have you decided if it’s a problem with the engine off yet?

I have the same setup with EFII and about the time I finished Phase 1 I started getting a loud buzz every time I keyed the mic. I replaced my ignition wires with ones that are designed for RF suppression and, sure enough, it went away. I suppose it could have been a bad crimp, but in any case, it worked.

Good luck
 
I good tool I use for checking antennas is a NanoVNA which one can get on Amazon for $60.

Here I am sweeping the entire band checking one of Don Pansier's excellent antennas. The cursor is showing SWR at 1.52 at around 122.900mhz.

There could be some bad crimps of the BNC connectors so I would also check at the radio end.

+1 on the NanoVNA. When playing with my home made comm antenna on turtle deck behind RV-4 canopy , it was amazing to see how sensitive (to SWR) antenna is to any object (or body) in the vicinity of it, including canopy open and closed.

Excellent tool for the price!

Finn
 
I don't think that his coax type or installation is at fault. His says his transmissions are good. That is one of the first places that antennae and coax and connectors would show up.
 
USB Chargers

Try unplugging the USB charger. I had an issue with an automotive unit that reduced my radio reception by about 75%.
Replaced it with an aviation compatible unit from Spruce and problem solved.

Cheers, Tom
 
Had a nearly identical problem with a Cirrus. It even persisted after the customer had the two GNS430's swapped for GTN750/650 combo. And new antennas were installed just before that.

It turned out to be the Spider Tracks device that had been in the plane for 3 years.

https://www.spidertracks.com/

Never underestimate the interference ability of LED's, USB devices, and now, tracking devices.
 
Radio issues

Does the airplane exhibit the same behavior with pilot and copilot headsets? Have you examined those pesky little fiber washers used with the mic and phone jacks?

Warren
RV7. 2014
 
We have isolated the problem to the key switch. Flew the plane up to 8500' and found an ATIS that was broken (in and out with a lot of static).

Shut off the engine with the fuel pumps (remember it's an EFII). No change.

Turned off the key switch and both radios were crystal clear and picking up the ATIS loud and clear.

We talked to Robert Paisley and he said he has seen some issues like that caused by the ethernet cables connecting the ECU's to the Control Panel. He suggested a Ferrite Bead on each ethernet cable, and possibly separating the ethernet cables from the wire bundles. We are going to try the Ferrite rings first (the clip-on kind probably).

Any thoughts?
 
Jessie,
Ironically enough, I had the same issue with my RV-10... both comms checked great on the ground.. then static in the air.. Initially both of my antennae's were mounted below the pilot and co-pilots seats.. Went through the typical troubleshooting.. ground's, WSR checks, etc.. I eventually moved one antennae to the aft fuselage. (thought it was a spacing issue) What I believed fixed my issue was two different mfg antennaes; one Rami and one Cobbam antennae. I can now pick up ATIS from a local airport 7 miles away on the ground with both comm's.
 
Jessie,
Ironically enough, I had the same issue with my RV-10... both comms checked great on the ground.. then static in the air.. Initially both of my antennae's were mounted below the pilot and co-pilots seats.. Went through the typical troubleshooting.. ground's, WSR checks, etc.. I eventually moved one antennae to the aft fuselage. (thought it was a spacing issue) What I believed fixed my issue was two different mfg antennaes; one Rami and one Cobbam antennae. I can now pick up ATIS from a local airport 7 miles away on the ground with both comm's.

We will try the two different antennas. I can't imagine that would change anything, though. We have MANY times put the antennas just where they are on this plane, always matching models, and never once had a problem like this. Again, the thing that took the noise away was turning off the key switch.
 
I don't think that his coax type or installation is at fault. His says his transmissions are good. That is one of the first places that antennae and coax and connectors would show up.

Poor quality coax will be much more sensitive to noise from things like USB chargers. That'll make a big difference on receiving, but very little on transmit.
 
Poor quality coax will be much more sensitive to noise from things like USB chargers. That'll make a big difference on receiving, but very little on transmit.

It's all new RG400 coax with dual crimp connectors.
 
Obvious question, sorry........ Did the noise start just after all new coax was installed?
 
Try changing the key switch. Don't know why it would work but at this point it can't hurt to try. :confused:

From what what I understand, it's not the key switch that's the problem, it's the systems connected to the key switch. What does the key switch actually do? Provide power to the EFII(s)? Any other systems?
 
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