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COM Transmit Issue Dynon SV-COM-C25

I have a Dynon system with the SV-COM-C25. The COM radio is connected to the PMA8000BT audio panel. My second COM is on my GTN750. The problem i have is that the MIC GAIN on the Dynon is set to max (100) and the audio level of the broadcasts is at best a 3/5. Most times less. The quality on the COM2 GTN750 is 5/5. I have swapped antennas but there is no difference and the both com radios use the same mic/headset so that can't be the problem. The system was working and then the problem occurred so i figure its not a wiring or grounding issue unless something came loose but we checked and all is well.

Besides changing the SV-COM-C25 does anyone have any suggestions as to what the problem could be?
 
Very timely post. I just found out this week that there are known issues with some of these radios. Lots of them are functioning perfectly but I don't know the rate of failure. I've been chasing similar problems with my Dynon Com for nearly 4 years now. I did similar troubleshooting as you, triple checked the wiring, swapped com1/com2 audio/PTT wires from the audio panel between Garmin and Dynon radios, swapped antennas and cables, the problem always stayed with the Dynon radio and the other was still OK. They replaced the first radio within a week of first flight back in Oct 2016 for the same complaints I still have. The radio replaced again last summer with their newest version, thanks to Rob Hickman at AFS when I stopped in for a visit during a vacation trip. I thought it was finally fixed but I still get complaints from ATC and other pilots on audio quality sometimes. Often the first 3 or 4 seconds of a transmission the carrier is present but there is no modulation. I had an avionics tech check the installation and everything was verified correct according to the installation manual. I have a digital in-line radio test set that measures transmit parameters (Tx power, modulation, VSWR, etc) and it shows the delay in modulation. Rx is always very clear.

Give Dynon support a call. They are great to work with. They are shipping a Trig radio to me at a cost of $450 and I have to return my current one. I assume it is a discounted price and I have to pay their cost or something since it is no longer under warranty, unfortunately. I'm not thrilled about the cost since it never worked properly but it will be an acceptable cost if I can finally be rid of this nagging problem. It should arrive soon.

Colin
 
Thanks Colin.

I had called dynon before and they appeared to be baffled by the problem. Interesting to know that there are known issues. They insisted that there was probably a grounding issue but we checked the connections and they were ok. I will call again. Please let me know if the problem is corrected
 
I've been having very similar sounding issues with my original Dynon COM radio. I had numerous issues with the radio back when I was doing Phase 1. Sent it in several times and finally Dynon just sent me a different unit and all has been well for the last 6 years. Never got a full diagnosis from Dynon, but we determined that the radio was not staying on frequency by using a digital frequency counter.

Recently I have been hearing from other pilots who hear me on the radio that I cut in and out and am sometimes unreadable. I am wondering now what it might take for me to get the newer Trig radio. Mine is definitely out of warranty, but for $450 a trade up would be appreciated.
 
I did the swap to the newer radio. Dynon supplied both a wiring harness adapter and a antenna connection adaptor. Swap was easy and no function issues. Clarity with the new radio was substantially improved.
G
 
It seems like the actual radio SV-COM-425 is a different physical size to the new SV-COM-X25 radio. Is that true? How did any of you adapt?
 
SV-COM-T25

My Trig/Dynon arrived yesterday and I installed it last night. I was fortunate enough to have made a mistake during my original sub-panel build up and grabbed the template for the transponder instead of the radio so I ended up with nutplates installed for either. Little did I know that my mistake would make my life very easy down the road.

It took me about a half hour to do the swap. I tested it prior and the Dynon radio was doing the same thing, dropping the first part of the transmission then crackling to life to get the last few syllables to the airwaves. Once I installed the new radio all my transmit problems disappeared.

The sidetone of the new radio doesn't seem as sharp as the original or the Garmin GTN but the transmission is very clear. During testing I was switching between my 2 radios and the listener could not detect a difference in either the strength or quality of the transmissions.

After replacing the radio twice, the coax, the antenna, the connectors, the wiring changes, the running of a braid between the case and the forest of tabs this is finally fixed. I'm happy Dynon finally admitted defeat here and made it right.
 
The new radio is a slightly different size and requires the mounting screws be redrilled. I had room at the original location so just redrilled the mounting screws.
On the subject of sidetone we had the same issue. It was very muted and hard to hear. For some reason when you install the new radio the sidetone volume goes to the lowest setting. Go into the Dynon setup menu and reset the sidetone to a higher level and your problem will be fixed.
G
 
X-25

Just for clarity, when the different size radio is mentioned, are you talking about the transceiver unit or the panel mounted controller? The Dynon photos look like the panel unit is the same. Since my transceiver is mounted the Av tray the size/shape difference doesn't matter. Thanks-
 
Yes, just the transceiver unit. I have a new one on it's way from Dynon and will report back on my installation.
 
Replacement completed.

I received the new unit today and installed it.

Here's what is in the box.
IMG_8587-M.jpg


I had to drill 3 holes for new screw locations.
IMG_8589_heic-M.jpg


The adapaters made this very simple. The hardest part was just figuring out where to mount it. My old unit was mounted horizontally on the forward side of the subpanel. The new unit fits vertically near the same location. The antenna coax uses a BNC to TNC adapter, and the connector adapter cable supplied hooked up with no problems.

IMG_8594_heic-M.jpg


I did a quick radio check then went flying and had no issues!
 
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