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Dynon Radio Weak and Broken - Ideas requested

rvator51

Well Known Member
I posted this on the Dynon forum but am also posting here as I am trying to troubleshoot this tomorrow so I can fly this weekend so apologies for the double posting:

My COM is being reported as weak, broken, missing every other word by pilots in the air and Unicoms on the ground. Its a new installation with RG-400 cable and a new VHF antenna from Delta Pop.

I hooked a SWR meter to it today and got the following readings:

118.000 Mhz 8.2 w power, -1.15 reflected power, 2.2 SWR

127.000 Mhz 2.6 w power -.66 w reflected power, 3.0 SWR

136.000 Mhz 5.5 w power 1.22 w reflected power, and 2.8 SWR

Is it normal to have such a big power drop midway through the frequency range? Is there anything these numbers say about possible causes for weak transmissions or area to troubleshoot?

I am using a new Zulu 2 headset and also tried with a DC headset.
 
This sounds very similar to my early experience with the Dynon COMM.

We put a radio frequency counter near the antenna. When you hold the PTT, it should send out a carrier frequency that is steady. The frequency counter said otherwise and you could see that the carrier was all over the place on certain frequencies. Some frequencies were more stable, and it was always uncertain whether or not anyone (tower) would be able to hear you fully when you were talking. Transmissions were essentially frequency hopping around too much to be heard.

I sent the unit back to Dynon twice. The first time, they said "no problem found", but it persisted. Second time they had it, I asked for a replacement unit in return. The replacement unit has been trouble free for over 3 years.

If you have access to a frequency counter, try transmitting on various frequencies and watch to see what the carrier is doing.
 
Last Fall I ferried a new experimental Super Cub with a Dynon Skyview and Dynon comm across the country. Enroute I couldn't talk to controllers on most approach frequencies but was loud and clear on most Unicoms and tower frequencies.

Once back home with the new owner we contacted Dynon for help. We removed paint and gasket from under the Delta Pop antenna and I added bonding jumpers to adjacent sheet metal panels to ensure good ground plane. I rotary brushed the paint off from around the underside antenna mounting holes. We replaced all coax connectors. We sent radio back to Dynon for analysis and/or repair. We tried Dynon-supplied notch filters inline with the dsub connector. After weeks of fiddling we finally got decent transmit results for the majority of frequencies. However, we were not able to ever get a good transmission on our local clearance delivery frequency (125.00). We gave up and started using Ground (121.90) and tell them we cannot communicate with clearance and ask them to relay a clearance instead.

Over the years I have successfully installed Garmin, Trig, Icom and King transcievers along with audio panels and intercoms in multiple aiframes from tube and fabric, aluminum and composite airframes. I thought I was versed in proper technique and troubleshot accordingly.

There is a definite frequency range where transmissions on the Dynon comm were very poor to awful. Meanwhile the balance of the frequencies were 5x5. I haven't had so much trouble with a Comm install with new equipment since experiencing the heartache only the MGL V10 could deliver. It was a good day for me when the owner sold the bird out of state a couple of months ago.

Jim
 
I had a similar problem, changed out the RG400 cable with new ends and all good, could not see or OHM any problems with the bad cable but it was the problem.
 
Over the years I have successfully installed Garmin, Trig, Icom and King transcievers along with audio panels and intercoms in multiple aiframes from tube and fabric, aluminum and composite airframes.

Jim,

It is a currently a Trig unit :D
 
Last Fall I ferried a new experimental Super Cub with a Dynon Skyview and Dynon comm across the country. Enroute I couldn't talk to controllers on most approach frequencies but was loud and clear on most Unicoms and tower frequencies.

Once back home with the new owner we contacted Dynon for help. We removed paint and gasket from under the Delta Pop antenna and I added bonding jumpers to adjacent sheet metal panels to ensure good ground plane. I rotary brushed the paint off from around the underside antenna mounting holes. We replaced all coax connectors. We sent radio back to Dynon for analysis and/or repair. We tried Dynon-supplied notch filters inline with the dsub connector. After weeks of fiddling we finally got decent transmit results for the majority of frequencies. However, we were not able to ever get a good transmission on our local clearance delivery frequency (125.00). We gave up and started using Ground (121.90) and tell them we cannot communicate with clearance and ask them to relay a clearance instead.

Over the years I have successfully installed Garmin, Trig, Icom and King transcievers along with audio panels and intercoms in multiple aiframes from tube and fabric, aluminum and composite airframes. I thought I was versed in proper technique and troubleshot accordingly.

There is a definite frequency range where transmissions on the Dynon comm were very poor to awful. Meanwhile the balance of the frequencies were 5x5. I haven't had so much trouble with a Comm install with new equipment since experiencing the heartache only the MGL V10 could deliver. It was a good day for me when the owner sold the bird out of state a couple of months ago.

Jim

Here are the power out by frequency:
118.000 8.7
119.000 7.8
120.000 5.8
121.000 4.4
122.000 3.3
123.000 2.6
124.000 2.4
125.000 2.5
126.000 2.4
127.000 2.5
128.000 3.0
129.000 3.7
130.000 4.9
131.000 6.5
132.000 9.1
133.000 11
134.000 10.8
136.000 5.5
 
Well well. I think we are on to something. Your lowest power reading corresponds with my failed 125.00 clearance delivery problem. The correlation of your results and mine, while inconclusive, could indicate the start of a trend.

I just installed a Trig TY91 in a Husky and have zero transmit issues on 125.00. Perhaps it is the Dynon ICS or system interface affecting the 123.0 - 127.0 frequency range.

Jim
 
I hooked a SWR meter to it today and got the following readings:

118.000 Mhz 8.2 w power, -1.15 reflected power, 2.2 SWR

127.000 Mhz 2.6 w power -.66 w reflected power, 3.0 SWR

136.000 Mhz 5.5 w power 1.22 w reflected power, and 2.8 SWR

Is it normal to have such a big power drop midway through the frequency range? Is there anything these numbers say about possible causes for weak transmissions or area to troubleshoot?

Hi Tom,

It seems to me that your SWRs are fairly high.
I know your antenna is rated at less than 2.2:1. (If it's the Red Tail VHF Com)See reference...
And your reflected powers are all above the typical 10 percent max.
I'd think the minimum power output would be at least 6 watts.
It seems very odd that the power droop would be in the middle...Typically comm antennas are designed to hit the sweet spot in the middle of the VHF frequency band (128 Mhz) with the outer frequencies hitting the max SWRs.(3:1 max)

Causes for poor SWRs are as follows...

Poor antenna grounding, damaged coax (sharp bends or kinked),bad connectors/connections, antenna bad or damaged, corrosion at antenna base, and water egress into coax and or connectors.

I'd concentrate on the coax and antenna installations.

jliltt gave good examples of what to check for...Bret pointed out coax problems.

Remember, the coax shield is just as important as the feed line. I'd probably still check the coax and connectors for shorts and resistance.

What we don't know...

Coax length and routing.(away from all other coax cables, especially transponder)
Antenna location.(3 feet away from other antennas)
Equipment model numbers for better accuracy.

References...

Antenna Specs
Antenna installation Advisory
MGL V6 and V10 Radio Installation

Best regards,
 
Hi Tom,


What we don't know...

Coax length and routing.(away from all other coax cables, especially transponder)
Antenna location.(3 feet away from other antennas)
Equipment model numbers for better

Best regards,

Hi T.C.

RG400 coax 5 ft long goes from left side of psnel to side and down to antenna month just in front of spar on left side of aircraft belly. Transponder is over 3 ft away on the front right side of aircrft belly.

Skyview 10" and 7" displays
Dynon intercom
Dynon comm
Dynon transponder
Dynon ADS-B in 470 mounted behind bagge compartment.

I built and put in a new cable and a Comant antenna today with same results on power. SWR 1.6 at low frequency goibgTo 2.2 at high frequency. 122 To 125 MHz was about 2 watts output again with higher watts output at both Low and high frequencies, which doesn't make sense to me.
 
Dynon Support Rocks.

Dynon Support really came through on this. A new radio is being shipped to me to use while mine is being inspected. Dynon says they actually ship the radios back to Trig to do the actual inspection/repair.
 
The end of the story...

The new replacement Dynon radio had same symptoms as my Dynon radio. Power low in midrange and high SWR. Pulled Dynon radio out and put in an old ICOM A-210 radio I have. Power meter showed higher power output but still high SWR and power higher and both ends of the frequency and lower in the middle just like the Dynon radio.

Bit the bullet and replaced my new Delta Pop antenna with a Comant antenna. I didnt want to do it because of having to drill new holes in my fuselage. SWRs with Comant antenna dropped from 2.7-3.0 before to 1.8-2.0 max SWR. Power went up in mid frequencies. Problem solved.

I dont know if the Delta Pop antenna is bad or if I just could not ever get a good ground on it. Tried everything.
 
Hi Thomas,

Great to hear a happy ending! Thanks for the update. Way to hang in there and nail it down!

I'm just a bit confused tho... Didn't you replace the antenna in post #9?:confused:

...I built and put in a new cable and a Comant antenna today with same results on power. SWR 1.6 at low frequency goibgTo 2.2 at high frequency. 122 To 125 MHz was about 2 watts output again with higher watts output at both Low and high frequencies, which doesn't make sense to me.

Best regards,
 
Hey, Tommycat, Yes, but I didnt mount the Comant on the belly because I didnt want to drill new holes so I mounted it in the center of a sheet of aluminum and laid the sheet on the wing figuring that would work as a good ground plane. Evidently it didnt.
 
Talk about coincidence

Our Dynon com radio worked flawlessly for 95 hours and then on the way to TX the transmissions became unreadable by the controllers. Long story short, we were told to check for a bad ground or coax. We sent the unit back to Dynon and were told the SV525 bench checked out perfect. Since we purchased the radio from Stein, I contacted him for further advice. Chris (at Stein Aviation) said to check the cable by connecting it to a second radio and see what happens. I hooked up my handheld today, flew 20 miles from the airport and the tower received me 5X5. We Will have our unit back Monday and I Will reinstall it with paint sanded off of the sub panel and a ground wire attached to check it out. Stein said if it still doesn't work, he will send a new radio to see if the problem is corrected. I Will report back on Tuesday to let you all know the outcome. Here's hoping.
 
We'll, MJ and I reinstalled the 525 module and it looks like everything is back to normal. We still have to flight test it but I think it will be ok. Thanks to Dynon, Stein, Chris and Nathan for all of the great advice.
 
We'll, MJ and I reinstalled the 525 module and it looks like everything is back to normal. We still have to flight test it but I think it will be ok. Thanks to Dynon, Stein, Chris and Nathan for all of the great advice.

Well, did Stein change or fix anything? Or did it check out OK?
 
Since we haven't flight tested yet, i don't if the returned unit is 100 percent. If it isn't up to par, Stein said he will replace the Dynon radio under warranty. I Will give a final report when the weather let's us get up in the air to make a final assessment.
 
Did a flight test today and everything is working 5X5. I do really like this radio because of all of the shortcuts and clarity. Cheers to Dynon and Stein.
 
Did a flight test today and everything is working 5X5. I do really like this radio because of all of the shortcuts and clarity. Cheers to Dynon and Stein.

Same question as earlier....:)

Well, did Stein change or fix anything? Or did it check out OK?
 
Stein never saw the unit. I sent it back directly to Dynon. Stein said that since I purchased it from him, he would stand behind the warranty if necessary.
 
Stein never saw the unit. I sent it back directly to Dynon. Stein said that since I purchased it from him, he would stand behind the warranty if necessary.

Ahh, thanks. So it was a Dynon factory fix/exchange that solved the problem...
 
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