Today's Message Index:
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1. 11:19 AM - Re: Transmit troubles on comm radios (Noel Loveys)
2. 08:21 PM - Re: Transmit troubles on comm radios (Tammy and Mike Salzman)
Message 1
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| Subject: | Transmit troubles on comm radios |
Do receiving stations (tower etc) hear the crackle on your transmissions? Is
the crackle only in your side tone. Do you hear the crackle on incoming
signals?
Noel
-----Original Message-----
From: owner-avionics-list-server@matronics.com
[mailto:owner-avionics-list-server@matronics.com] On Behalf Of Dave Lammers
Sent: Tuesday, September 22, 2009 11:04 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.
>
>
>
Message 2
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| Subject: | Re: Transmit troubles on comm radios |
Hi Dean,
There is a Garmin service bulletin out for spurious RF emissions. See link: SB
0921
Regards,
Mike Salzman
Lancair ES
Fairfield, CA
________________________________
From: DEAN PSIROPOULOS <dean.psiropoulos@verizon.net>
Sent: Monday, September 21, 2009 9:54:31 PM
Subject: Avionics-List: Transmit troubles on comm radios
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......SNIP............
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