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AIDC-3733 Noise Figure and Gain Measurements



I recently made NF and gain measurements on three unmodified AIDC-3733 
downconverters using a calibrated laboratory NF system. All three 
indicated a NF around 2.3 dB and gain of 30 dB at 2.401 GHz. NF 
readings were later confirmed by performing sun noise measurements. 

The NF at 2.401 GHz can no doubt be improved by re-tuning the comb 
filter. My experience with homebrew S band equipment on AO-13 
indicates that a downconverter with a 2.3 dB NF will work nicely 
(with a suitable antenna) with AO-40 when the spacecraft attitude 
problems are corrected. I chose not to re-adjust the comb filter.

FWIW, I could not perform meaningful sun noise measurements using a 
Yaesu FT-817. Although the AGC was turned off, there was an indication 
of a second active AGC loop. I'm sure the 817 will make a nice 
portable IF radio for use on the microwave bands.

Gene Marcus W3PM GM4YRE
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