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  #1  
Old 08-04-2017, 05:28 PM
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Default Dynon Radio Weak and Broken - Ideas requested

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.
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  #2  
Old 08-04-2017, 08:30 PM
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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.
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  #3  
Old 08-05-2017, 06:24 AM
jliltd jliltd is online now
 
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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
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  #4  
Old 08-05-2017, 01:50 PM
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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.
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  #5  
Old 08-05-2017, 02:05 PM
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Quote:
Originally Posted by jliltd View Post
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
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  #6  
Old 08-05-2017, 06:22 PM
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rvator51 rvator51 is offline
 
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Quote:
Originally Posted by jliltd View Post
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
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  #7  
Old 08-05-2017, 08:14 PM
jliltd jliltd is online now
 
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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
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  #8  
Old 08-06-2017, 03:31 PM
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Quote:
Originally Posted by rvator51 View Post

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,
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  #9  
Old 08-06-2017, 07:54 PM
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rvator51 rvator51 is offline
 
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Quote:
Originally Posted by Tommycat View Post
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.
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  #10  
Old 08-07-2017, 11:33 AM
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rvator51 rvator51 is offline
 
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Default 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.
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