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How exactly does a CW rig work?

Jan 17th 2017, 17:23

KE0KCG

Joined: Aug 25th 2016, 00:00
Total Topics: 0
Total Posts: 0
Hi All,

Based on my question, you can probably tell I'm new to the concept. I understand that a key is used to turn the transmitter on and off. How does that result in the tones I hear on my receiver from distant stations? I don't see how simply keying up a transmitter produces the result heard on a receiver.

Cheers,
Chris
Jan 19th 2017, 04:19

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Chris -

For CW reception, the receiver mixes the incoming signal (a pure RF frequency, with on-off keying) with another frequency, called the "local oscillator" -- or in older rigs, the "beat frequency oscillator". (A mixer generates a signal having a frequency equal to the difference or sum of two input signal frequencies.) The local oscillator is more-or-less the frequency that your receiver tuning dial reads. (I'm simplifying here.) If you tune 500 Hz off from the incoming signal, you will hear a 500 Hz tone, with the same on-off keying. As you tune slowly back and forth, the tone frequency will vary according to the offset from the incoming signal.

I hope that helps a little.

73 Martin AA6E
Jul 2nd 2017, 21:08

KE0KCG

Joined: Aug 25th 2016, 00:00
Total Topics: 0
Total Posts: 0
@AA6E thanks for the info! I guess that's what the BFO option is on my Drake 2B!

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