[Boatanchors] Pair of Crystals needed

[Bill Cromwell]

On 03/08/2014 11:39 PM, hwhall at compuserve.com wrote:
> Could he perhaps get away with using a crystal or crystals in a VXO type oscillator? The VXO maybe could be adjusted to pull crystal(s) that are close onto the desired frequencies.
>   
> Wayne
>
>   WB4OGM
>
>
Hi Wayne,

A crystal in that range won't pull very far. I thought about that a 
along time ago. Crystals don't pull very far and the amount they will 
pull is a small percentage of the operating frequency. So, the higher 
the frequency the farther they can be pulled. The exact amount will vary 
a little from crystal to crystal. At forty meters they are good for 
around three to five kilocycles. That scales to around about 200 or 300 
Hz at 455 kc. So basically you already need to have the xtal cut for the 
frequency and can maybe adjust to compensate for the strays in your circuit.

I have found that it doesn't need to be a division of gnat's whiskers. 
The L-C oscillators running near 455 kc as the BFO can be stabilized to 
be better than "good enough". Tube or solid state. Otherwise the best 
choice is probably those programmable oscillators that others have 
mentioned or build your own PLL or DAC oscillator referenced to a more 
readily available crystal.

Good luck with your project.

73,

Bill  KU8H