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XMIT on oen Comm making RX on other light up?

dreed

Well Known Member
Hey folks- just added a 2nd Comm while down for first conditional. Now I have IFD540 as COMM 1 and Dynon as COMM 2 (was only comm before). Antennas are both belly mounted side by side about 18" (need tot measure) apart.

I was using COMM 2 (TX/RX) on Tue flying back and COMM 1 was on RX on guard. Pilot buddy in right seat noticed the IFD rx light triggering on guard when we'd transmit on the Dynon. I need to check and see if we see the same behavior if we switch the transmitting radio

Is this normal behavior given the radios are so close and one is so close it's blowing through (don't know the correct term to use) the other one even though they are not on the same freq?

If not- any recommendations.

Thanks in advance
 
Most likely, yes. 18” is pretty close.
Some radios (not familiar with yours) have a pin labeled ‘transmit interlock’ or ‘receiver inhibit’ or ‘receiver reduced gain’ or something like that. If yours do, run a wire from the com1 PTT line to the com2 interlock pin; and another from the com2 PTT line to the com1 interlock pin. That will fix the issue.
 
As a very broad based rule of thumb, no other antenna should be closer than the length of the antenna.

IOW, No other antenna should be closer than 21" from a 21" long antenna.

As Bob said, 18" is pretty close to another com antenna.
 
Dan

I just installed a GNS480 as my primary COM with my SL-30 as my secondary COM and when I transmit on the SL-30, the RX light on the 480 lights up but when transmitting on the 480, the RX ( T ) light on the SL-30 doesn't light up with no major adverse effects..

Sometimes I may have a little of noise in the 480 when transmitting on the 480 with both radios volume up, if I turn the volume down on the SL-30, no more noise....Turning the volume down does basically the same thing as the interlock.

I have a Top and Bottom antenna on my RV-4 ...

The 480 & SL-30 don't have built In interlock...Depending which Dynon Com you have, it may/ may not have built in interlock.

Bruno
 
Thanks All-

Our little strip 1W1 is shut down today for a "wings and wheels" event and I have a few small things I need to address- I'll get an accurate measurement and check the suggestion of the interlock wire. I'll reach out to the folks at Advanced too as I have an Advanced panel and most of the radio wiring runs through the ACM and they put it all together.

Need to verify the Dynon/Comm gets and RX when the Avidyne 540 is transmitting as well
 
Our antennas are belly mounted as well. We get cross talk if both radios are tuned within about 2 Mhz. So if radio one is transmitted on 121.0, as long as radio 2 is tuned above 123.0 its good to go. It's our work around until I can get the PTT interlock jumpers installed.
 
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