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Occasional Com Radio Issue

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B2C2 View Drop Down
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    Posted: 16 May 2018 at 3:51pm
I have had an on and off problem with the radio quality on my 540 for a year or so and was wondering if anyone else has seen this. Once in a wile, I believe after a bit of a sit but haven't had it happen often enough to verify this, I will get comments from ground etc that my 540 com radio is 1 by 5. Reception is fine. I have two radios so I switch to the other one and all is good. Then it seems like after I power cycle the unit, typically next startup on the same day after a flight somewhere its fine. As you might imagine its not easy to diagnose this when the avionics shop is at another airport. So far it seems like it goes away by itself and I haven't been able to get it to do it at the shop. We checked all antenna connectors, tray etc and no obvious problems found. Has anyone else seen anything like this or have a suggestion of what might be causing it?    
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AzAv8r Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2018 at 10:53pm
I have had two incidents of something similar, both in mid February of this year.  The IFD was installed ~ Jul 15.

The first time I was contacting Ground for a day VFR departure, sitting near our hangar.  After several tries with no response, Ground replied "Aircraft repeatedly attempting to contact ground, nothing but a squeal." I switched to #2 (a Garmin SL30), Comms was fine, and we departed.  Later in the flight I did a radio check on the IFD with ATC and all was well, so we used the IFD for the remainder of the flight.  I attributed the issue to having the perfect (unlucky) position in an aluminum (hangar) canyon, out of line-of-sight from the tower, to maximize any of a number of RF distortions (I started life as a radio engineer).

Three days later departing a different airport, and sitting on a wide-open ramp in clear line-of-sight to the tower, Ground replied to my initial attempt "weak and unreadable".  I again switched to #2, and was successful.  We departed VFR on #2.  After a while in the flight, we switched back to the IFD and did a radio check with ATC.  No issues, so we used #1 for the remainder of the flight. 

Subsequent flights have revealed no issues.   Still scratching my head, and wishing I'd bought a lottery ticket.   Right now I'm assuming a defective antenna connection somewhere, but intermittent problems are difficult/expensive to track down until you discover the magic sequence that makes them repeatable.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote HenryM Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2018 at 11:16pm
i had a similar problem in a non-IFD-equipped plane. The root cause in my case was a loose ground connection. I accidentally found it when I touched a nut on the firewall that turned when it was supposed to be tight. We had spent a couple of hours chasing the bug right after an engine monitor installation in a Cessna 172. We were chasing leads related to the engine monitor installation which had not even touched the area where the loose ground was found. 

The loose ground caused the radio signal to react as described. Fortunately the ground was loose enough that it was not as intermittent as the problems described here. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PA20Pacer Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2018 at 7:07am
You have probably already thought about this, but often the #1 comm is wired to an antenna on the bottom of the plane. On the ground, it is possible for the plane to be positioned so that a wing or another part of the airframe is blocking the signal.

Regards,

Bob
Bob Siegfried, II
Brookeridge Airpark (LL22)
Downers Grove, IL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote compasst Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2018 at 11:39am
I experienced transmission clarity issues on my first IFD 540 shortly after it came out. Turns out it was a problem that required warranty work.

I knew it wasn’t antenna issues because the previous radio worked fine on same antenna and wiring.

Give tech a call and ask for Christine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote B2C2 Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2018 at 7:49pm
Ill try calling tech support. Given the extremely intermittent nature of the problem I'm not sure what they will say but its worth a shot. When you had this problem that was fixed under warranty was it also intermittent or predictably present?

In regards to one of the previous posts when I had the problem the other day i tried the radio again from a different spot on the field prior to departure to see if I was being blocked on the antenna due to the hangars nearby and had the same problem. Next time I'm going to power cycle the radio stack and see if it fixes it. I had a passenger with me and didn't want to unduly delay the flight with trouble shooting.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Plunger Quote  Post ReplyReply Direct Link To This Post Posted: 3 hours 9 minutes ago at 10:33am
I have a new IFD 440 with a different problem and can't get Avidyne Tech support to help me with. My situation is that the comm radio in the 440 has poor reception.I compare it to the comm 2 which is a 20 year old radio which receives perfectly. I swapped the antenna cables, for both radios but that didn't help. Next the avionics shop swapped out the 440 with a new unit off the shelf but the reception was still poor with the replacement radio. Next we reinstalled my old Garmin 430 and the reception was perfect.I have not replaced the coax cables or antennas yet.

Not sure what to do now. Rolland from Avidyne won't return my calls, the Avionics Place in Rockford is stumped. Not sure Avidyne was a good choice.

Anyone have any ideas?  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 8 minutes ago at 1:34pm
I have never heard of anyone (customer, or shop) not getting return calls from Tech support, when they had an outstanding problem.

There is no general issue with the IFD COM section, if there was, it would have shown up a long time ago.

The thing that is common here would be the mounting tray. The fit on the IFD and GNS are a little different. I would bet that replacing the tray (if you didn't use the nice new IFD tray), might solve the problem.

Just a guess.

* Orest



Edited by oskrypuch - 8 minutes ago at 1:34pm
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