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[aprssig] Mic-E and HTs

Scott Miller scott at opentrac.org
Tue Dec 13 21:10:49 UTC 2005


Ok, now you've got basically what I came up with.  Only I wasn't able to get 
PTT detection directly from the I/O pin (this was with a Motorola GP68 
handheld, don't remember the troubleshooting sequence exactly) so I added a 
transistor there.

The only problem I've encountered with this setup is that the audio is lower 
than I'd like.  Larger values for the capacitor help, but I think I'm still 
going to have to add an op amp or transistor there.

But my question remains - has this always been the accepted way of doing it? 
Why isn't there any documentation out there about it?

Scott
N1VG

----- Original Message ----- 
From: "Robert Bruninga" <bruninga at usna.edu>
To: <wa8lmf2 at aol.com>; <aprssig at lists.tapr.org>
Sent: Tuesday, December 13, 2005 12:59 PM
Subject: Re: [aprssig] Mic-E and HTs


>>> wa8lmf2 at aol.com 12/13/05 1:37 PM >>>
>bruninga at usna.edu wrote:
>>Ill draw it...
>
>I don't see how the second half of your diagram
>(the part labled "Combined PTT" could possibly work.
> You show one side of the mic element grounded all
>the time with PTT button then grounding the other
>side, thereby shorting out the audio.

Argh, your right.  I was too quick to draw that.
I fixed it now with the typical 2.2k resistor...

http://www.ew.usna.edu/~bruninga/mic-ePTT.GIF

sorry,
Bob






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