Loss of Radio Transmission

[Ikarus]

While flying this past weekend I lost the transmission capability of my Skyview radio. I had to revert to looking for a green light from the control tower to land!!!

A few facts:
- was flying through rain when it apparently had the problem
- no apparent loose connections anywhere
- both headsets still work and transmit button shows TX on screen
- no settings were changed
- testing with the skyview settings showed the system was picking up the mic transmissions from "marginal" to "good"
- later testing showed some transmissions but only for about 1-2 miles to a handheld radio

Any suggestions from anybody of where to start looking for problems? It has been a great radio for the past 3 years and still receives from over 50 miles with a simple little antenna.

Thanks in advance for any help.

 

[jakej]

Is the aircraft a composite airframe ?

 

[Garrett]

I would check the connector at the antenna end. If it was exposed to the rain and not water tight water can wick itself in and corrosion sets in, especially since there are multiple metals involved in the connector. Dissimilar metals = galvanic corrosion which shorts the output to ground. You can also put a watt meter in line to check output power and the reflective. If there reflective it is probably the connectors possibly water in connector or maybe a smashed cable. A avionics shop should have a watt meter to test with. Hope this helps

 

[Ikarus]

Thanks for the ideas but the connector was the first thing I checked. It looks as good as ever. I took the metal wire antenna out and sanded it smooth and tightened it in place again to no avail. Might have to go to the avionics shop like you suggest.

The plane is a fiberglass body over an aluminum structure.

The fact that it happened while it was raining is definitely suspicious but I am positive the radio didn't get wet itself. (I have also flown through rain before) No settings were changed so I am reluctant to just start playing with those either. It simply doesn't transmit as far as it used to. What causes or controls that??? Hmmm...

 

[jakej]

Nothing to do with radio getting wet ! Ever heard of p-static ?  Look it up 
I had the same issue once while flying IFR in my Glasair, lost comms with ATC - I could hear them sometimes but they could not hear me.  Never had that problem since.
Without being able to look over your installation I feel there could be other factors too, a shop with the right equipment/skills may be the best option.

 

[Ikarus]

P-static might be a possibility but it hasn't gone away. The radio is now permanently just transmitting short distance.

I guess a trip to an avionics expert might be necessary.

 

[jakej]

The ‘tip’ re p-static was more an FYI as well. I’m figuring, from the unchanged symptoms, that you transmitter had had an issue similar to what happens when transmitting without the antenna connected.

 

[Ikarus]

Well - I wasn't able to solve my problem.

Therefore, Dynon agreed to exchange the whole radio under warranty! New unit installed and working like it always did - lots of range for both transmitting and receiving.

However, the DUAL function doesn't seem to work smoothly. When on DUAL, lots of static and clicking is heard unless a transmission is being received. Might have to send it back again....

 

[Raymo]

The clicking is normal when on dual receive. Mine does the same.

 

[xprsav8r]

Just a thought... You mentioned, "simple little antenna" in the original posting.

When was the last time you performed an SWR analysis?

You typically find warning labels on radios stating not to transmit without an antenna attached. That's because whereas receiving from any range involves amplification of sound inside the radio, transmitting involves converting sound waves to electromagnetic waves away from the radio. The antenna acts as a heat sink of sorts in the transference and transmission of electricity. An improperly tuned antenna may not dissipate heat adequately for the frequency range (118 - 137 Mhz) and may damage a radio over time -- hence near vs. far.