[aprssig] Mic-E and HTs

Robert Bruninga bruninga at usna.edu
Tue Dec 13 14:51:24 CST 2005

Ah yes, I see now.  I was assuming the the old
PTT line was the combined line for HT's.  Not
realizing that it was the audio out line.  duh...
I was reading the "audio out" line as the audio
*from* the PIC, not *to* the radio.  My bad...

Back under my rock..  Bob

>>> ve7gdh at rac.ca 12/13/05 11:52 AM >>>
Bob WB4APR wrote on Dec 13 2005

> Also, I notice in the TT3 schematic that the 2.2k
> resistor that mixes the audio and PTT for
> combined handhelds seems to be in the wrong
> place. It should be in series with the Q1
> output so that the Q1 does not load down
> the audio. As shown, the audio is essentially
> shorted by the PTT transistor when it keys.

I don't think so. PTT OUT goes to pin 3 of J1 for radios with dedicated PTT.
Note that where it says AUDIO OUT after C1, it is connected to AUDIO OUT on
pin 1 of J1. On most HTs (non-Kenwood), the PTT is essentially via R8. When
used with a mobile or Kenwood HT, R8 shouldn't be installed.

Did I get that right? <g> Not enough sleep for the last week.

73 es cul - Keith VE7GDH
"I may be lost, but I know exactly where I am!"

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