[aprssig] Bad Wiring diagram?

Stephen H. Smith wa8lmf2 at aol.com
Mon Mar 11 19:00:45 EDT 2013

On 3/11/2013 4:25 PM, Robert Bruninga wrote:
> Bad mini-DIN wiring diagram?
> Connecting my D700 to my APRStt engine tonight I noticed the most prevalent 
> wiring diagram for the D700 data connector PG5A found on the web is wrong.  
> It shows both the 9600 and 1200 baud radio outputs connected together.
> Yet the D700 manual has a warning "Connecting both PR1 and PR9 (1200 and 9600 
> baud outputs) together will cause the TNC to malfunction".
> Yet that note is not shown on ANY of the dozens of pages that refer to this 
> wiring diagram:
> http://www.cqham.ru/0imgs/5060yq.jpg
> So, if anyone has ever had problems with their external use of the Mini-Din 
> connector to the radio, then this might be why.  Amazing that this kind of 
> error can be out there for over a decade and be the most widely referenced 
> drawing on the internet!
> S

This diagram is obviously wrong with only a cursory glance.

The "9600 baud" pin is just raw non-demphasized non-squelched  FM discriminator 
audio; i.e. a DC-coupled direct connection to the radio's discriminator.

The so-called "1200 baud" pin is actually de-emphasized and squelched audio 
exactly like what comes out of the speaker but at a fixed level unaffected by 
the RX volume control.    Note that on all-mode CW-FM-AM-SSB rigs (FT-857, 
IC-706, TS-2000, etc) the "1200" baud pin is live in all modes, while the"9600" 
baud one is live only on FM where the discriminator is in use.

In other words, wiring these two pins together is essentially shorting the FM 
RX discriminator output to the output of one of the audio driver stages.

Full details on the 6-pin mini-DIN "data"/"packet" connector (which is really 
just audio connections + PTT + SQUELCH), including a downloadable PDF-format 
pin-out diagram of the jack, is here on my website:




Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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