[Boatanchors] Microphone

[Bob Macklin]

There should be a COMMON (C) contact on the switch. Use that instead of the 
NO contact to connect to the shield.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "David C. Hallam" <dhallam at knology.net>
To: <Boatanchors at mailman.qth.net>
Sent: Friday, February 08, 2013 12:43 PM
Subject: [Boatanchors] Microphone


>I have a wiring problem with an EV 619 High Z dynamic PTT microphone.  I 
>have it connected to a 3 wire (2+ braid shield) cable.  One side of the 
>element is connected to the center wire, the other side is connected to the 
>braid shield. The PTT switch contacts short the element on receive and 
>remove the short on transmit.  The other wire in the cable for PTT is 
>connected to an NO contact on receive and a NC contact on transmit.  The NC 
>contact is connected to the shield.
>
> The problem is on transmit with no audio to the microphone, there is a 50 
> mV or so PTP signal from the microphone.  That is putting a 6V DC walwart 
> on the PTT wires and looking at it with a scope.  When I remove the DC, 
> the output from the microphone is normal with no output unless I speak 
> into the microphone.
>
> I have looked carefully several times and the PTT switch wiring and don't 
> see any shorted wires or other problems.
>
> I am baffled.
>
> David
> KW4DH
>
> -- 
> A democratic government is the only one in which those who vote for a tax 
> can escape the obligation to pay it.
> Alexis de Tocqueville
>
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