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From: drassew2@interalpha.co.uk
Date: Fri, 26 Mar 1999 13:32:20 GMT
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: 137 Carrier
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Reply-To: rsgb_lf_group@blacksheep.org

>At 10:01 26/03/99 -0000, G3XDV wrote:
>>On a similar subject, it would be really useful to be able to plot 
>>signal strength against time (say, 24 hours) using a computer - for 
>>simplicity it would help to use the sound card so that the same 
>>connection can be used as Spectrogram.


For anyone who built the PIC based DSP interface (April 1997 RadCom) you
have suitable recording hardware to hand.  Just feed the AGC voltage
conditioned to 0 - 5 Volts directly to the PIC input pin - disconnecting
audio op amp buffering and audio gain of course.  The OP amp could be used
for the voltage conditioning but I'll that to individuals to sort out.  An 8
bit word representing this voltage level is then sent along the RS232 port
at 10 kHz or whatever sampling rate is set.   I wrote some logging software
for this (somewhere in the 'JNT archives) that reads the serial interface at
prescribed intervals and logs the data to disc.  This was actually done at
the time for mains voltage monitoring but that's another story.  If anyone
is interested I'll look it out or write some more suitable logging software.

With the advent of Gram and 56002EVM boards, this 8 bit interface is
obsolete for DSP now but I supplied at least 40 pre-programmed PICs any many
others requested the software to blow their own devices so a number must be
lying around on shelves unused.   
With a PIC software modification, and changing the clock crystal to a 3.6864
MHz device it can be used for sampling at 7200 Hz for the VE2IQ BPSK
software instead of the rather inelegant interface circuitry described - but
I believe even this mode used the soundcard now!  

Andy  G4JNT