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Old March 14th 07, 05:47 PM posted to rec.radio.amateur.homebrew,sci.electronics.basics,sci.electronics.design
[email protected] cs_posting@hotmail.com is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 3
Default VCXO frequency isn't high enough

On Mar 13, 12:02 pm, "Anthony Fremont" wrote:

I believe this is direct conversion and that the crystal should exactly
match the desired station (3581kHz) I want to recieve, that's right isn't
it? Maybe this is close enough? I have to wait til tonight to see if I can
actually hear anything.


Depends on what sort of signal you are trying to receive.

To receive a single our double sideband signal (or, in a very touchy
way, an AM one), you want your direct conversion receiver's local
oscillator exactly on the transmitter frequency.

But to receive a CW signal, you want your local oscillator 700 Hz or
so above or below the transmit frequency. That will cause you to hear
a 700 Hz audio tone for the CW.

Unless I'm mistaken, 3.581 MHz is in the CW portion of the 80 meter
band.
If you can get to 1 KHz below the transmitter, you should be able to
copy CW as 1KHz audio. If you can only get to 1.5 KHz below, you'll
get 1.5 KHz audio... not ideal listening, but probably workable.