Did you try rewiring the mic element so that it is powered all the time?
Maybe the mic power is going through the PTT switch and the turn-on
transient is putting out an audio pulse.
On 12/18/2010 10:50 AM, K8JDC wrote:
> I recently got a Tentec 700 hand mic and noticed that it causes the
> radio to transmit a spike every time the PTT lever is pushed. The mic
> was set up to use a 9V battery when I got it but I have wired it to
> operate directly off my Paragon II. It spikes on either power source
> and the spike is basically full output power so it's a bit alarming.
> I originally thought the spike was related to the operation of the
> PTT switch...i.e. a little clicking noise causing the spike but that's
> not true. If I key the PTT with the mic disconnected from the radio and
> then connect the mic to the radio, the spike still happens so it appears
> that it is related to applying the voltage to the mic circuit or
> cartridge. I played around a bit trying to add a capacitor to stabilize
> the power in the circuit and eliminate any transients but the spike is
> still there.
> Has anybody seen this and/or have a fix? The existing caps in the
> circuit appear to be okay (i.e not shorted) and I think the cartridge
> itself is the cause of the spike. There is a resistor feeding power to
> the cartridge but I have not tried raising the value (yet).
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