I have an Avidyne 540 for a #1 comm and a KY-97 for a #2 comm.  Both are connected through the Avidyne 240 audio panel but as far as I'm currently aware that's the only common element in the radios.

I was flying about 1000 nm last week (yes, home from OSH) and at least half a dozen times I lost the ability to hear incoming comm on BOTH radios!  It happened while with Chicago center, Minneapolis center, Kansas City center, and Fort Worth center; I don't think there were all having transmission issues on the same day.  Here's what I know -

1. All would be quiet and I would get an urgent call from either center or another airplane center had pressed into service to help contact me.  When I would answer I could always hear fine and the transmissions from other aircraft and center with both strong and clear.

2. Other times it was the reverse, things would be quiet and I would key up for a radio check.  Two or three calls later I would hear the response and they would always tell me they heard every request and responded each time.  I only heard after several responses.

3. I switched to my backup radio and had the same thing happen!

4. At one point I turned an ATIS freq that was nearby and monitored.  Things were fine for a while and then the transmission stopped.  The RX indicator on the 540 was not lit.  When ATIS was again audible it was the same broadcast as before.  The time was not the appropriate time for a change to ATIS.

5. While I do not believe my airplane was hit by lightening, it was parked in the North 40 at OSH all during the week and there were a few strong storms that passed near the area.  Heavy rain and strong winds were common and a few rumbles of thunder.  I don't camp at the airplane so I wouldn't know how it was at that exact spot during the storms.

As far as I know now there are no common parts between the radios other than the 240 audio panel.  However, that should not inhibit the RX light on the 540 even if it blocked the audio from coming through.  Also, my with was with me and we could always talk to each other - which was easy in times of silent radios!

Lastly, being a long trip I brought an MP3 player and plugged it in through a music input jack through the 540.  The music never stopped playing (I pressed the 'music' button on the 240 so the music doesn't mute during radio transmissions) so I know there wasn't a loss of all sound.

Have you tried reseating the audio panel to insure it's making contact with its connectors.

Were you using one of those cigarette lighter USB chargers to charge your Ipad, phone, etc...?

Gene

Gene, an interesting question and one that would not seem obvious to me even to ask.

However, I do have a remote ADS-B receiver that I haven't used since I got the full Avidyne system installed, since it can broadcast to my Ipad.  At OSH this year I got thinking about redundancy and decided to plug it in through the lighter port and it was plugged in and turned on for the entire trip; it's a Clarity box.  I almost never use a USB charger on my flights so this was another difference between this flight and all the others.  Have you experienced a connection between those chargers and intermittent radio reception?

There are lots of reports (Beechtalk) of interference being caused by these cheap USB chargers.

The issue is that they use a switching power supply design to reduce the voltage from 10-30 Volts DC to 5 Volts DC and if not designed carefully, it will generate harmonics that will be right at the 100-138 MHz range.  Right where the COMM frequencies reside.  Harmonics in this case means unintended noise in the frequency range. 

That certainly could explain why both radios failed to receive normal broadcasts.  That is, the harmonics were too strong and overwhelmed the weaker broadcasts.

I would go fly again without the charger and see if it issue goes away.

Keep us posted on the results, please.  Curious minds want to know!!!

Gene

"The Witch Doctor"

Gene,

What you said sounds plausible and I was using a new charger that I hadn't used in the airplane before.  I would not have thought about that device but it was the only thing I had introduced to the flight deck that wasn't there on previous flights.  I guess the ADS-B receiver hadn't been used since the Avidyne equipment was installed but it seems that would be well documented and it never caused issues with radios in the past.

I'm going to power up the airplane and listen to ATIS for a time without the device and then plug it in and see if there's a change.  I will certainly post after that test and let you know how this turns out.

Thanks for rattling those beads, my witch doctor friend :)

Rick

https://www.amazon.ca/Anker-PowerDrive-Charger-Bluetooth-Headsets/dp/B00VH84L5E/ref=sr_1_16?ie=UTF8&qid=1533826841&sr=8-16" rel="nofollow - https://www.amazon.ca/Anker-PowerDrive-Charger-Bluetooth-Headsets/dp/B00VH84L5E/ref=sr_1_16?ie=UTF8&qid=1533826841&sr=8-16

What app do you use to get traffic an d weather from the IFD to your iPad? I'd really like for ForeFlight to be able to display this information.

Rick

Be sure to put a load on the USB charger.  Connect your Ipad or the ADSB-IN receiver to the USB charger.

Gene

I still haven't made it to the airport yet to check the device, but with all the talk about these charging units it appears to be a solid link.

The charger I was using that day has no manufacturer printer.  Instead it says SpencerAircraft.com

Hmm ... I think I would do some quality control checks before putting my name on a product.  Just sayin'

Good point, Gene, I'll be sure to load it up like it was on the flight.

I wondered about using the charger in my car and using a handheld transceiver.  Would the result be the same as running the aircraft radios?  I suppose there's no solid link, though, if the radio doesn't cut out it doesn't mean the aircraft radios would have been the same.  I guess I just need to spend time at the airport.  Darn, darn, darn :)