Mike,

This problem is likely caused by Radio Frequency feedback into the
headset from
your transmitter. The transmitted RF field is fairly strong in the
cockpit;
something in the headset demodulates the RF and the resulting audio
feeds back around into the comm radio making the squeals.

It will be worse on some frequencies than others. Sometimes a radio
connected to an antenna on the top or top front of the cabin will be
worse. More power in the transmitter will be worse. The SL-30 has
more RF power than the '97 so could easily be more susceptible.

In Bonanzas, with the batwing antenna right over the cabin, and all
that glass, RF feedback is particularly troublesome.

I once had a Plantronics mic with a small wart on the cable that had
the problem. I wrapped the wart (which had all the semiconductors
that rectify in it) with sticky copper tape and that fixed the
problem.

I've seen the problem a lot with Telex headsets. For awhile they
were the worst. I thought they had solved this problem long ago. It
is a design problem. A headset should be designed with margin
and be bullet proof enough to work in any cockpit without feedback.

The Bose I (and to a smaller extent the X models) have sensitivity to
the frequencies used by ATC radar. When you are sitting on the
ground near one of those rotating antennas, you can hear it zip by
every time it points in your direction. But these headsets are OK at
the usual
VHF frequencies we transmit on, so there is no feedback with them.

It is true that if your cabin speaker is on while you transmit (very
unlikely)
that you could get acoustic feedback and lowering the mic gain might
fix it. But changing the gain will have little effect on RF feedback.

Bill Hale BPPP instructor bppp.org K0QA
Zillions of headset types flown in BPPP clinics


On Apr 29, 4:23*pm, "Mike Noel" wrote:
Adjusting the mic gain made no difference and so the headset went back to
Telex for warranty repair (36 month warranty on the Stratus 30 and 60 months
for the Stratus 30XT). *I'll report back later on my warranty repair
experience with them.
It's a nice headset at a moderate price so I hope I can report back
favorably.

--
Best Regards,
Mike.

http://flickr.com/photos/mikenoel/"Mike Noel" wrote in message

...

My Telex 30 headset and SL30 nav/com have developed a loud and annoying
oscillation during xmit. *The tone is both obvious in the headset
side-tone
and also is heard by other's listening on the frequency.

I've tried two other headsets (a DRE ENR and a non-ANR headset) and both
work fine with the SL30. *My com2 is a King 97a and it works fine with all
of my headsets, including the Telex.

The problem seems to have developed in stages over the past several
months.
First I was noticing the Telex and SL30 would occasionally give my voice a
hollow sound for the first few transmissions of the day, then sound fine.
Finally last week the tower controller mentioned the squeal which I was
also
noticing. *It tends to go away after a bit but it sounded odd for the
entire
flight.

Has anyone experienced a similar problem? * I'm hoping to try a few other
brands of headsets this weekend to see if the headset is the likely
culprit.

Best Regards,
Mike.

http://flickr.com/photos/mikenoel/