[HomeBrew] Panadaptors

[Ray Anderson]

John-

>From your description it sounds like the crystal is functioning
as a simple roofing filter to filter the output of the
mixer before it is fed to the diode detector.

A single crystal used as a filter won't provide a really
great passband shape, but will scrape off a lot of the
unwanted responses coming out of the mixer prior to
the detection stage.

73,
	Ray  WB6TPU
	

>
>Many years ago I constructed a very simple Panadaptor,
>so I could see about 500 KHz of each band I used.  It has
>been so long since I used it that I have forgotten the purpose 
>of the crystal in the last receiver stage of the adaptor.  Anyone
>who might be able to help, I will gladly send you the schematic.
>
>As I recall, the unit samples the output of the first mixer in the\
>Rx, and heterodynes it with a local HFO that is swept in sync
>with the sweep of the display CRT.  Then come a stage of
>intermediate frequency amplification, then this crystal stage, then
>a diode detector to drive the vertical plates of the CRT.  I wonder
>if the crystal is used as a second mixer to rescale the sample to
>original frequency, since the crystal matches the offset of the HFO
>from the sample exactly.
>
>Any assistance appreciated
>
>John
>
>
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