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Re: Pseudo-Sine?

 

Amazing what you can find in the forum archives with a little digging.
The audio oscillator thing on the Collins KWM-2 only sorta worked slick,
though I don't personally have any objections if you want to do it this way on a QRP rig.?

Jerry, KE7ER


From post? ?/g/BITX20/message/22372

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Dennis Kidder W6DQ
02/21/17???#22372??

Collins did, indeed, use an audio tone to generate CW in their early S-Line equipment.? The Collins design fed the sidetone oscillator into the audio section on the KWM-1, KWM-2/A and 32S-1/2.? And if you know the history of this, they realized the "error in their ways," and soon went to a different design. If the balanced mixer is not properly nulled and/or the filter passband is off a bit, the result can be three carriers!? Many amateurs using this equipment on CW received "pink tickets" from the FCC.???
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Collins changed the design with the 32S-3/A.? Today, CW is not recommended with the 32S-1/2 or KWM-2/A radios without careful monitoring of the output signal.
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The earlier Collins KWS-1 (Collins Radio's first amateur SSB transmitter) produced CW by inserting the BFO signal AFTER the bandpass filter, bypassing the balanced modulator a well.? This produces a very clean output.
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Don't get me wrong -- I am not saying NOT to use an audio oscillator to generate CW -- I?AM?saying that you need to be careful and understand the potential problems it can produce.? Personally, I am choosing to insert the keyed BFO signal, with proper shaping, after the crystal filter to generate CW, bypassing the TX first mixer and filter.? Keep in mind that the TX and RX frequencies will be zero beat unless provision is made to shift either the TX or RX when going from TX to RX.? I believe adding RIT is a probably an easy solution here.? Of course, I will also need to add sidetone.
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Thanks to all for maintaining such a great forum for a great little radio!
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73,

-dennis W6DQ
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On Mon, Mar 4, 2019 at 02:00 PM, Tim Gorman wrote:
Evan,

IIRC this is how the old Collins KWM-2 used to do CW. Injection of an
audio tone. Again, IIRC that's how you did the spot function on cw, turn
on the audio osc and zero beat it with the received cw signal.

Worked slick for the KWM-2. Should work with the ubitx as well! It
would be a simple add-on.

tim ab0wr
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