[Hammarlund] Xtal Frequency Question

[Robert R. Kerr]

The resonant frequency of the crystal will be somewhat dependent on the 
characteristics of the circuit external to the crystal, i.e., if you 
have external capacitance in parallel with the crystal, it will lower 
the resonant frequency of the composite circuit relative to the 
resonance of the crystal alone.

I think in this application the best thing to do it align the receiver 
IF to the resonant frequency exhibited by the crystal in the circuit.

Bob
WB4TGG

K3PID wrote:
> I have determined that the 455 KHz HC-6 crystal that is used to form the filter in my HQ-145 is about 1 KHz low. That's about 1/455 or 0.2%.  I also noted that the marking is 455 kcs while I can purchase one marked 455.0 kcs. The extra decimal would imply another digit of accuracy. 
>
> QUESTION: Is that pretty typical? Since I can easily align the IF string to match the 454 KHz filter, and I can also adjust the LO to be in calibration, is there any significant downside to running with the 455 KHz IF a KHz low? Should I spring for the 455.0 Xtal? If I wanted to get real adventuresome, I could open it up and polish off a little which would raise the frequency. Haven't done that is 30 years and never with an HC-6 can.
>
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> K3PID
> Ron H.
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