SSB rig idea using cheap filters

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From: Wayne Burdick (burdick@interval.com)
Date: Thu Jun 17 1993 - 14:25:32 EDT


As an alternative for using the cheap 10.7 MHz SSB filters discussed
recently, how about using an 18.000MHz crystal (about $1 from digikey) in a
VXO circuit, and subtract to get to the 10.7 MHz I.F. In other words:

        18.0 - 7.3 = 10.7

The VXO crystal can easily be moved down to 17.95 MHz, so you can tune from
7.25 to 7.30, i.e.:

        17.95 - 7.25 = 10.7

Since this is a subtractive mixing scheme, you'll need the USB BFO crystal
to get LSB reception. (Hopefully someone is checking my math here!)

I don't think there will be any birdies at all with this mixing scheme, and
as a bonus, the image frequency gives you USB operation on 10 meters
([17.95->18.0] + 10.7 = [28.65->28.7]). If you don't mind paying $13 for a
custom 17.900 MHz crytal (try JAN crystals, 800-526-9825), the range
becomes 7.15->7.2 and 28.55->28.6 MHz. Anyone in the mood to build a 40/10
SSB QRP rig?

73,
Wayne, N6KR

Wayne Burdick Interval Research Corp.
wayne@interval.com 1801-C Page Mill Road
(415) 354-0928 Palo Alto, CA 94304


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