Today's Message Index:
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1. 06:34 AM - Re: Transmit troubles on comm radios (Dave Lammers)
2. 08:39 AM - Re: Transmit troubles on comm radios (Ron Raby)
Message 1
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| Subject: | Re: Transmit troubles on comm radios |
It might be as simple as a poor ground from the PTT switch to ground
Regards,
Dave Lammers
DEAN PSIROPOULOS wrote:
>
>
> 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 (all metal
> 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.
>
>
>
Message 2
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| Subject: | Re: Transmit troubles on comm radios |
Dean
I had a very similar problem. It turned out to be a poorly crimped pin on a
purchased harness. Try inspecting at all the related connectors and pins.
Ron Raby
Lancair ES
----- Original Message -----
From: "Dave Lammers" <davelammers@mchsi.com>
Sent: Tuesday, September 22, 2009 9:33 AM
Subject: Re: Avionics-List: Transmit troubles on comm radios
>
> It might be as simple as a poor ground from the PTT switch to ground
> Regards,
> Dave Lammers
>
> DEAN PSIROPOULOS wrote:
>> <dean.psiropoulos@verizon.net>
>>
>>
>> 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 (all metal
>> 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.
>>
>>
>>
>>
>>
>>
>>
>
>
>
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