Skyview dual coms tx rx issue

[mruffatto]

I've installed two coms and I'm testing them in my garage. RV7 with two delta pop aviation antennas mounted on the belly. Dynon intercom. Harness built according to the manual. RG400 coax.

When I transmit on com 1 it breaks the squelch on com 2. Different frequencies. Same vice versa. I have to turn the squelch setting up to about 80% to prevent receiving on the other com. I'm assuming this is too high?

They operate independently without any issues.

Any advice on trouble shooting?

Thanks
Mike

 

[Carl_Froehlich]

There are a boatload of things to check - but first move the plane out of the garage to see if you still have the problem.

Carl

 

[mruffatto]

I tried that yesterday. No change. I also swapped out the coax runs. I only had one cable so I tried each side independently. No change. The antennaes are installed with star washers and I checked for good contact. I double checked the isolation of the jacks from the airframe.

I did find that if I diconnected com2 antenna will transmitting on com1 it did not have any issues.

 

[Carl_Froehlich]

While there are many issues to rule out, I'd first look at the antenna systems (antennas, feed lines and connectors). Assuming you have > 12" of spacing between antennas then it is time to see if the antenna systems are operating correctly. If you have a ham radio friend ask him to come over with an antenna tester like an MFJ-259C: http://www.amazon.com/SWR-Antenna-Analyzer-MFJ-259C-0-53-230Mhz/dp/B00IRPMLTS/ref=sr_1_1?ie=UTF8&qid=1433168385&sr=8-1&keywords=mfj+antenna+analyzer

Connect the analyzer at the radio end of the coax.

In the meantime if you have another antenna to temporary connect to one radio at a time with your spare cable, even a handheld rubber ducky will work, and see if the problem changes or not.

I assume you did the simple continuity checks to make sure the coax and connectors are good, not shorted, etc.

Carl

 

[dynonsupport]

Mike:

Likely the two antennas are so close to each other that the transmit COM simply "overwhelms" the other COM in Receive mode; there's simply too much RF energy for the receiver to deal with.

Here's our relevant section of guidance for installation of dual COMs:
* Separation of COM antenna from another COM or NAV antenna: Recommended separation between COM antenna(s), NAV antenna(s), and ELT antennas is 6 feet (72 inches). Minimum required separation between antennas is 4 feet (48 inches). Ideally, install the primary COM antenna on the lower fuselage, and install the secondary / standby COM antenna on the
upper fuselage. 

(Page 16-17, SkyView System Installation Guide, Revision U)

I've installed two coms and I'm testing them in my garage. RV7 with two delta pop aviation antennas mounted on the belly. Dynon intercom. Harness built according to the manual. RG400 coax.

When I transmit on com 1 it breaks the squelch on com 2. Different frequencies. Same vice versa. I have to turn the squelch setting up to about 80% to prevent receiving on the other com. I'm assuming this is too high?

They operate independently without any issues.

Any advice on trouble shooting?

Thanks
Mike

 

[mruffatto]

Is it possible that low voltage/ weak battery could be the contributing to the problem?

I charged up my battery and started trying things again. It seems to be working fine now.

 

[Dynon]

There's no direct implication from a weaker battery, but can can theorize possibilities there. But two other things are more likely: First, how far apart were the radios tuned, and how close are your antennas? It's not unexpected that if the tuned frequencies are close, and the antennas are also close, that you could have a transmission from one radio open up the squelch of another radio on a close frequency. There's just too many watts too close to each other. This is one reason why aircraft com antennae are often on opposite sides of the aircraft (belly / top) vs just being separated by a couple of feet.

Also, the garage environment is ripe to bounce / contain the signal, so that's not really representative of the real world environment either.