[amsat-bb] RE: S band for 6 bucks

["Woody" <kj4so@xxxxxxxxx>]

Hi All:

I replaced the crystal in the Cal Amp 13215 downconverter today and all 
went very well.  Observing the LO output on a spectrum analyzer, the 
signal is strong, clean, & stable.  The crystal was manufactured by JAN 
and is slightly low in freq.  The LO is 2.25588 MHz. instead of 2.256 
MHz.  I prefer "International Crystal" crystals, but I already had the 
JAN crystal.

With an input level of -70 dB, the 144 MHz. IF output level is -38 dB. 
This is the same level that the unmodified Cal Amp 130215 downconverter 
shows with an input of 2.5 GHz.

I retuned the combline input filter and touched up the LO reference 
crystal's trimmer capacitor to get the LO as close as possible to 2.256 
GHz.  I have not made, nor do I plan to make any other adjustments or 
modifications to the downconverter.

I have modified several Drake, AIDC, and other models of Cal Amp 
downconverters.  This downconverter is the simplest one that I have 
modified so far.

The seven-pole combline filter on the input is very impressive. 
Properly
tuned, it should really help to keep unwanted signals out of the 
downconverter's input.

Thanks again, Drew for the "heads up" on the $6 S-band downconverters.

73,

Woody
KJ4SO
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