Yo Paul,
Actually it's Ferg, but the error is easily made, not that it
matters that much
It is difficult to assess from here because different makers assign
different terms to various functions. I will await your scouring the manual
for any clues.
Basically, I think your problem is acoustic feedback, but RF feedback may
also be present. The latter is less likely with transistors than with tubes,
so I think your earphones may be leaking excess volume to the region of the
mike. VOX in a Stearman is a constant problem because of the large
background volume of the engine in an open cockpit.
Also, there is always 'noise' in an electrical/electronic circuit
(called internal noise) due to ions and so forth jumping about but always
worse in tubes than transistors. The squelch is installed to make the mike
insensitive to this and that's the "threshold" for sensitivity. Noise below
that doesn't get through. The other datum sets the level at which your voice
triggers the audio. It gets sticky beyond that, but the Squelch knob on the
front usually sets the level at which external noise shuts off the mike -
but then perhaps I'm being too simple.
Let's see what the manual says - probly makes an ass of my remarks.
Ferg
----- Original Message -----
From: "Paul McAllister" <paul.mcallister@qia.net>
Subject: Re: Europa-List: Feedback problem with the radio
<paul.mcallister@qia.net>
|
| Hi Fred,
|
| To answer your question my set up has a push to talk for transmitting. If
| your theory is correct I should be able to improve the situation by
reducing
| the microphone gain. The GX60's internal intercom has the following
| parameters that can be set:
|
| - RF Level
| - Headphone level
| - Side tone level
| - Intercom level
| - Intercom squelch
| - Noise level
|
| I was hoping to set one that said "Microphone gain", but alas no. I will
dig
| out the manual tonight and see if any of the above settings might help.
|
| Cheers, Paul
|
|
| ----- Original Message -----
| From: "Fergus Kyle" <VE3LVO@rac.ca>
| To: <europa-list@matronics.com>
| Subject: Re: Europa-List: Feedback problem with the radio
|
|
| >
| > Paul,
| > It can sometimes be transmitted through tight clamping of
| units
| > in the system, but this does not sound like that symptom. If your
headset
| > earcups 'leak' then the acoustic feedback would be the cause. Tight
| earcups
| > tend to reduce that.
| > Is your system operated as 'VOX' - voice-operated
| transmission?
| > That is, do you have the sound of your voice open the transmitter, or do
| you
| > press a transmitt button? If the former, the sound from nearby will
| trigger
| > the transmitter open as well as the intercom. VOX is operated by two
datum
| > voltages - a large one which triggers the transmission and a smaller one
| > below which the transmitter shuts off. Both of these voltages is set by
a
| > pair of potentiometers usually somewhere moderately available to the
| > avionics bod who installs/repairs same. The same may apply to the
intercom
| > unit.
| > We'll keep an eye open for your solution when it comes.
| > Cheers, Ferg
| > ----- Original Message -----
| > From: "Paul McAllister" <paul.mcallister@qia.net>
| > To: <europa-list@matronics.com>
| > Subject: Europa-List: Feedback problem with the radio
| >
| >
| > <paul.mcallister@qia.net>
| > |
| > | Hi All,
| > |
| > |
| > | I have an odd problem with my GX60 when trying to transmit. I found
it
| > would start oscillating, it would start with an echo and then break
into
| > full audio feedback, similar to as what a PA system does when the
| microphone
| > is too close to the speaker. I fooled with the problem for the longest
| time
| > and I finally narrowed it down to my LightSpeed headsets. I called
| > LightSpeed and sure enough they knew about the problem. They invited me
to
| > send the headsets back and they would fit a new shielded battery box.
| They
| > came back and they "sorta" worked, but unfortunately they would still do
| it.
| > |
| > | A this point I resigned myself to using my Telex 3500's. These always
| > seemed to work, but today they started to exhibit the same problem...
now
| I
| > am in a bit of a quandary on how to trouble shoot this problem. I do
not
| > have an audio panel at this time, I am using the internal intercom in
the
| > GX60.
| > |
| > | Does anyone have any ideas where to head with this.
| > |
| > | Paul
| > |
| > |
| > |
| > |
| > |
| > |
| > |
| >
| >
|
|
|
|
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