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Attention S-Band Downconverter "Tinkerers"



The following link is a used CalAmp d/c that has been sold on eBay one-at-a-time for a a few months now.  I bought one just to see what it was.  I don't know how many the seller has.

http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1294295274

The device has the "standard" MMDS frequency conversion scheme, so 2401 MHz is heard at 123 MHz in the stock configuration.  I checked it out on local MMDS TV signals and found it to be of average gain (sorry, can't quantify it), maybe equivalent to a Drake 2880 or Norsat 2500.  The LO crystal is soldered, so lifting the board would be required to replace the crystal with a 8.8125 MHz one.  The filter is traced on the board, so any of the popular resonant-frequency-reduction methods would work just fine here as well.

What is interesting, though, is the built-in antenna construction.  It has a round patch (linear) antenna with a short feedhorn assembly built right into the case and directly connected to the RF-amp on the d/c circuit board.  It also has a parasitic array of "washers" that screws in ahead of the patch.  Throw away the washers-array and the basic d/c+patch would make a pretty nice all-in-one feed for a dish antenna.  Maybe one of the patch guru's could design a replacement patch to bolt right inside the housing to get circular polarity.
73,
Jerry, K5OE



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