good info, but the questions beg to be asked...if audio tones can be used
for afsk on all these digimodes, why not vfsk/dfcw/qrss etc. the audio is
just audio. while i know that there is some small problems with overdriving
the tx and generating spurious tones, why can not vfsk/dfsk use the same
techniques as all the other modes?
i confess i am not a programmer, so dont know about what is involved, but if
one program can do it and not cause problems, then another could also be
made to act the same.
david
-----Original Message-----
From: [email protected] <[email protected]>
To: [email protected] <[email protected]>
Date: Wednesday, February 07, 2001 22:13 GMT
Subject: LF: CW-Keying via Soundcard or PC speaker
Hello Rik, hello group,
Consider this for 'audio keying' a transmitter to generate CW (morse code
with
ON/OFF keying) or DFCW (morse code using AFSK):
As long as you keep the audio frequency higher than half of your
transmitter's audio bandwith, you will not have problems -whatever waveform
you are using, because the harmonics of the audio wave would be out of the
TX
passband. You could even use a square wave (which is the only possibility
for
the PC speaker).
If you use an audio frequency lower than half of the TX audio bandwith,
your
signal will be audible on at least TWO frequencies if there is the
slightest
harmonic distortion. And, on 137kHz, this unwanted emission will most
certainly be 'out of band'... (made that experience myself a few weeks
ago).
So, if possible, stay above 2kHz, then you don't even need a sine wave.
The problem with Win95 (and later stuff) is, programming the speaker is not
as easy as under the good ole DOS, because direct access to the hardware
ports is almost impossible (at least for a 'well behaving' windoze
program).
If necessary, I could include a 'QRSSS' audio keyer in SpecLab, but I guess
Rik is the 'expert' in this business and I don't want to invent the wheel
twice.
73's Wolf.
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