Obaid Vanjara Posted July 27, 2022 Report Share Posted July 27, 2022 Hi All, We seem to be having intermittent radio issues. Use Case: We do a radio check on the ground (be it with folks in the pattern or even with a hand-held) the reply is 5/5 - Clear We fly in the pattern and do a radio check, the feedback we get is little scratchy but readable We fly out (2500 feet) and it's almost unreadable by NorCal and a tower we were flying to would not even respond back to us (maybe they could not even hear us). We have two radios in the stack (older) and It’s the same (switching to either). I can remove and re-do the intercom/headset wiring but I am wondering if it’s a radio issue or potentially an antenna issue or something else? Trying to figure out what I can do before we take it to an avionics shop to troubleshoot. Anyone who may have had similar issues in the past? Quote Link to comment Share on other sites More sharing options...
PT20J Posted July 27, 2022 Report Share Posted July 27, 2022 Sounds like you have low transmit power since it works fine nearby by not in the distance and you seem to be able to receive OK. It's probably not the antenna since each radio should have it's own antenna and the chances of two being bad are low. It could be caused by something in the airplane causing interference. Try turning off all the other nav and com radios and see if it has an effect. It might also be caused by low voltage if the older radios have linear power supplies. Skip 2 Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 28, 2022 Report Share Posted July 28, 2022 Given separate radios, feedline, and antennae but BOTH radios exhibit the issue, I'm with @PT20J thinking this points to low voltage. Do you have a voltmeter in the panel? If not, I'd try to hook one up as close to the radio(s) as you can, read the voltage during receive (should be at least 13.7 Volts with the engine running) and then when you transmit. If you see over a 1 volt drop, I would be concerned. (A KX155 needs 8.5 Amps at 13.75 to reach its rated 10Watt transmit power) 1 Quote Link to comment Share on other sites More sharing options...
M20F Posted July 28, 2022 Report Share Posted July 28, 2022 2 hours ago, MikeOH said: Given separate radios, feedline, and antennae but BOTH radios exhibit the issue, I'm with @PT20J thinking this points to low voltage. Do you have a voltmeter in the panel? If not, I'd try to hook one up as close to the radio(s) as you can, read the voltage during receive (should be at least 13.7 Volts with the engine running) and then when you transmit. If you see over a 1 volt drop, I would be concerned. (A KX155 needs 8.5 Amps at 13.75 to reach its rated 10Watt transmit power) Where does the OP say separate wiring or antennas? The only thing I am clear that they have 2 of is 2 radios. Quote Link to comment Share on other sites More sharing options...
MikeOH Posted July 28, 2022 Report Share Posted July 28, 2022 3 minutes ago, M20F said: Where does the OP say separate wiring or antennas? The only thing I am clear that they have 2 of is 2 radios. Well, how many two radio installations have you seen where only one radio is usable at a time? 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 28, 2022 Report Share Posted July 28, 2022 Welcome aboard Obaid! 1) What radio are we discussing? Make and model…. 2) Learn how to R&R it…. It only needs a hex wrench for most…. 3) Spray contacts with contact cleaner… 4) Then expand the search to the rest of the antenna connections… 5) Be on the look out for the type of wire used for the antennas… many are getting replaced with the latest standard…. 6) If the plane is new 2U… don’t be surprised if you have ancient wire left from previous radio in stations that may not be the right spec…. 7) Antenna problem areas can often be found at the ground plane… see how much corrosion you have getting in the way… 8) get familiar with your volt meter and ohms meter… Something has gotten old and dirty… try to figure out what it is… then have your shop fix it without the hunt… PP thoughts only… any more complex… seek the services of a local radio guy… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
BobbyH Posted July 28, 2022 Report Share Posted July 28, 2022 If your antennas and power supply check out good you may be getting some RMI (Radio Magnetic Interference). To help troubleshoot it I would also try testing it at different engine RPMs and see if that makes a difference. If so I would look at your power source i.e. alternator and ensure it is functioning properly. It will also help the avionics shop troubleshoot it even if the alternator isn't a problem. Bob Quote Link to comment Share on other sites More sharing options...
EricJ Posted July 28, 2022 Report Share Posted July 28, 2022 It sounds like whatever it is is likely to be common to both radios, which eliminates the radios themselves and the antennas. That does suggest that the power supply or grounds are good first place to look, but there are a lot of other things that are common to both. OTOH, if we're talking about a pair of KX170s or something similarly old, it def could be radios. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted July 28, 2022 Report Share Posted July 28, 2022 Any chance of checking them with someone far enough away while your engine , transponder, and other radio is off? You could eliminate most of the rmi sources and isolate the issue to the radio or to engine/alt/etc. Another option is to pull your field/VR CB and turn off most other stuff to see if that changes/helps. Isolate the problem to what’s causing it. 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted July 28, 2022 Report Share Posted July 28, 2022 I’ll be the odd man out, and am not avionics expert. Work from easy to difficult, start with removing the antennas and checking that you have clean ground between the antenna base and the fuselage skin. Skin corrosion starts with poor sealing of the antenna base. Next would be the coax cables, radio ground and power connections. Clarence Quote Link to comment Share on other sites More sharing options...
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