deltamike197
Member
Hi all:
Maybe you can help with my transmit problems. I have a UPS Aviation Technologies (now Garmin AT) radio stack with SL-30 Nav Comm, GX-65 GPS/Comm, SL-70 transponder and SL-10MS audio panel (actually a PS-6000 with UPS AT nameplate). I checked out everything according to the installation manuals while the airplane was sitting on the ramp and the engine NOT running. Now that I've been flying a lot, I'm getting a crackling in the sidetone and when I look at the "TX" light on the radio it's flickering as if someone were pulsing the press-to-talk switch 4-5 times per second, even though I'm holding the PTT down tight. This happens on both radios and people in the pattern say I'm breaking up and garbled. I've tried several things looking for a solution, they are:
1) Turn down the MIC gains on both radios (in steps, a little at a time, over several flights). In the end I had them turned down so much I couldn't get a side tone in the earphones and suspect no-one could hear me at all.
2) I tried a couple different headsets (inexpensive non ANR types, Sigtronics and Pilot Avionics units, both around 15 years old but well taken care of and worked just fine in the Cessnas I used to rent). No joy.
3) I tried both headsets with and without foam muffs over the microphones. No difference that I could tell with or without the muffs.
4) Placed ferrite beads over both coax lines running to the transmit antennas (about 3/4 of the way down to the antennas, don't have access to the base of the antennas right now, but will when I remove the floor panels for annual inspection). No help!
5) Shut off the field in my B&C LR-60 alternator (with external regulator) to operate on battery only. No change (I'm using forest of ground tabs ala AEC philosophy and I'm NOT getting alternator noise in the reception of either radio so I didn't expect this to help but it was easy to test).
6)Since I used fine (24 gauge 5 condutor MAC servo cable, no shielding) wire to take the PTT signal from the PTT on the control stick to the pilots mic jack, I thought maybe that was causing a problem so I tried using the passengers PTT (wired with 22 ga shielded tefzel) instead of the pilots. No change.
7) The audio panel has a built in fail-safe feature that routes the PTT and mic/earphone signals direct to the number 1 NAV/COM in the event of audio panel failure. I shut off the audio panel and tried that. The NAV/COMM TX light comes on but still flickers and is crackly so it's not that. I of course could not test the #2 radio this way but would expect it to be the same.
Transmit antenna location is under the belly of the airplane (RV-6A). Two Comant bent whips about 40 inches apart just aft of the wing spar.
The GPS portion of the GX-60 and VOR/ILS portion of the SL-30 work just fine. Comm reception on both radios is loud and clear (at least I can hear people in the pattern even if I can't talk to them).
When I originally ran through the installation checkout I left the settings on the radios at the factory recommended (transmit worked fine so I left the settings alone) and have been making changes to the Mic gains only. These are computer controlled radios so I'm wondering if I need to adjust any other parameters such as squelch (no pots to control squelch like the old days) after making the Mic gain adjustments. Could the two be somehow related through logic in the computer program that runs the radios?
I'm really stumped, any suggestions? Any UPS AT radio stack users have this problem? How did you fix it? Should I run through the installation checkout with the engine running so as to have more noise impinging on the microphone while making adjustments? Don't like the idea of head down in the cockpit with engine running but I can tie down the airplane while doing the checks (I'm talking ground running here not trying to make adjustments in flight)! Thanks for the help.
Dean Psiropoulos
RV-6A N197DM
Flying and tweeking.
Maybe you can help with my transmit problems. I have a UPS Aviation Technologies (now Garmin AT) radio stack with SL-30 Nav Comm, GX-65 GPS/Comm, SL-70 transponder and SL-10MS audio panel (actually a PS-6000 with UPS AT nameplate). I checked out everything according to the installation manuals while the airplane was sitting on the ramp and the engine NOT running. Now that I've been flying a lot, I'm getting a crackling in the sidetone and when I look at the "TX" light on the radio it's flickering as if someone were pulsing the press-to-talk switch 4-5 times per second, even though I'm holding the PTT down tight. This happens on both radios and people in the pattern say I'm breaking up and garbled. I've tried several things looking for a solution, they are:
1) Turn down the MIC gains on both radios (in steps, a little at a time, over several flights). In the end I had them turned down so much I couldn't get a side tone in the earphones and suspect no-one could hear me at all.
2) I tried a couple different headsets (inexpensive non ANR types, Sigtronics and Pilot Avionics units, both around 15 years old but well taken care of and worked just fine in the Cessnas I used to rent). No joy.
3) I tried both headsets with and without foam muffs over the microphones. No difference that I could tell with or without the muffs.
4) Placed ferrite beads over both coax lines running to the transmit antennas (about 3/4 of the way down to the antennas, don't have access to the base of the antennas right now, but will when I remove the floor panels for annual inspection). No help!
5) Shut off the field in my B&C LR-60 alternator (with external regulator) to operate on battery only. No change (I'm using forest of ground tabs ala AEC philosophy and I'm NOT getting alternator noise in the reception of either radio so I didn't expect this to help but it was easy to test).
6)Since I used fine (24 gauge 5 condutor MAC servo cable, no shielding) wire to take the PTT signal from the PTT on the control stick to the pilots mic jack, I thought maybe that was causing a problem so I tried using the passengers PTT (wired with 22 ga shielded tefzel) instead of the pilots. No change.
7) The audio panel has a built in fail-safe feature that routes the PTT and mic/earphone signals direct to the number 1 NAV/COM in the event of audio panel failure. I shut off the audio panel and tried that. The NAV/COMM TX light comes on but still flickers and is crackly so it's not that. I of course could not test the #2 radio this way but would expect it to be the same.
Transmit antenna location is under the belly of the airplane (RV-6A). Two Comant bent whips about 40 inches apart just aft of the wing spar.
The GPS portion of the GX-60 and VOR/ILS portion of the SL-30 work just fine. Comm reception on both radios is loud and clear (at least I can hear people in the pattern even if I can't talk to them).
When I originally ran through the installation checkout I left the settings on the radios at the factory recommended (transmit worked fine so I left the settings alone) and have been making changes to the Mic gains only. These are computer controlled radios so I'm wondering if I need to adjust any other parameters such as squelch (no pots to control squelch like the old days) after making the Mic gain adjustments. Could the two be somehow related through logic in the computer program that runs the radios?
I'm really stumped, any suggestions? Any UPS AT radio stack users have this problem? How did you fix it? Should I run through the installation checkout with the engine running so as to have more noise impinging on the microphone while making adjustments? Don't like the idea of head down in the cockpit with engine running but I can tie down the airplane while doing the checks (I'm talking ground running here not trying to make adjustments in flight)! Thanks for the help.
Dean Psiropoulos
RV-6A N197DM
Flying and tweeking.
