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Sunday, 31 January 2010

501-504kHz LO for Field Strength Meter


As per previous post about 500KHz (http://m1kta-qrp.blogspot.com/2010/01/500khz.html), based loosely on PA0SE field strength meter which is a DC RX just built a 4MHz LO and used a 74HC4040 and divide by 8 to obtain 500kHz. Video of the initial 4MHz oscillator here:
video
Current playing with the required L and Variable C in series with the crystal that might allow the 4MHz oscillator to be pulled from 4.008MHz to 4.032MHz. I think probably too far for the crystal oscillator version so I might look at using a ceramic oscillator next.
Yes this is the oscillator circuit from M0MBU FEt TX for 500KHz which you might be able to make out in the background.
I'd prefer to keep it simple but if no luck then the next option will be a K5BCQ Si570 DDS VFO with frequency readout that will be fed into the divide by 8 logic of the 74HC4040.

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