Linux-Hams archive - September 1998: Re: soundmodem ptt circuit

Re: soundmodem ptt circuit

Hamish Moffatt (terhi.victor@logonet.com)
Sun, 6 Sep 1998 11:24:39 +1000

On Sat, Sep 05, 1998 at 08:30:00PM -0000, Mike Bilow wrote:
> Hamish Moffatt wrote in a message to Mike Bilow:
>
> HM> I see -10.9V on RTS. I see -0.61V on the base of the 548,
> HM> but 0V on the collector (no audio connected) and hence 0V on
> HM> the tip of the plug.
>
> HM> Any idea what might be wrong?
>
> A very American question: is a BC548 NPN or PNP? Which is the collector? :)

It's NPN. Unfortunately I couldn't work out how to put the arrow on the
emitter.. :-)

Turns out that it does work anyway; whoops. Originally I hadn't connected
the analog & digital grounds together, and it didn't work, but after I did
I just measured the voltages with the multimeter and assumed it didn't work.
Jaakko Koivuniemi suggested current might be more important, so I tried
it and it worked. Don't I feel stupid :-)

thanks,
Hamish VK3TYD

-- 
Hamish Moffatt, StudIEAust              terhi.victor@logonet.com, wilbzjy.yoxnicoxh@emengine1.com
Student, computer science & computer systems engineering.    4th year, RMIT.
http://hamish.home.ml.org/ (PGP key here)             CPOM: [*******   ] 73%
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