From: DL4YHF@aol.com
Message-ID: <9c.b79b2c8.27b31b6f@aol.com>
Date: Wed, 7 Feb 2001 16:43:11 EST
Subject: LF: CW-Keying via Soundcard or PC speaker
To: rsgb_lf_group@blacksheep.org
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

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.