[ARC5] Keying Approach

[AKLDGUY .]

Possible reason with carbon mike is that it cuts off current through
the carbon granules. You don't want current flowing at all times, even
with the modulator B+ cut off, since that would lead to shorter mike
life.

73 de Neil ZL1ANM



On Thu, Jan 15, 2015 at 10:08 AM, Robert Eleazer <releazer at earthlink.net>
wrote:

> Here is a question about something I have wondered about for some time.
> From what I have seen, aircraft PTT mikes typically use a DPST and key BOTH
> the mike line and the PTT line.  In other words, the mike is not connected
> to the transmitter until the button is pushed that also grounds the tip of
> the PL-68 and completes the transmit keying circuit as well.
>
> I am aware that some amateur radio transceivers simply turn the mike on
> with the PTT switch in series with the mike and that completes the circuit
> required to cause the transmitter to come on and the receiver to go to
> standby.
>
> Is it possible that the aircraft PTT approach reflects that on some
> transmitters just connecting the mike to the transmitter is enough to turn
> on the transmitter or is there some other reason?
>
> Wayne
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