[aprssig] Mic-E and HTs

[Robert Bruninga]

Scott,

I think that the 2.2k is negotiable, depending on the
rig.  THe larger the resistor, the less load ing on the
mic.  I hope someone else has looked at all the rigs
and decided what the typical PTT pulldown impedance
is supposed to be?  Bob

>>> scott at opentrac.org 12/13/05 4:10 PM >>>
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






Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      14400    [Think bottom of the 2M band]
Home Page:          http://wa8lmf.com 

"APRS 101"  Explanation of APRS Path Selection & Digipeating
  http://webs.lanset.com/wa8lmf/DigiPaths 

Updated APRS Symbol Chart
  http://webs.lanset.com/wa8lmf/miscinfo/APRS_Symbol_Chart.pdf 


New/Updated "Rev G" APRS     http://webs.lanset.com/wa8lmf/aprs 
Symbols Set for UI-View,
UIpoint and APRSplus:








_______________________________________________
aprssig mailing list
aprssig at lists.tapr.org 
https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig 



_______________________________________________
aprssig mailing list
aprssig at lists.tapr.org 
https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig