G4DDK VLNA for 1296 MHz
When I saw results of N/F reached by Sergej RW3BP with VLNA of Sam G4DDK, I was looking for some possibility to improve also my N/F in VLNA. After the build of original kit from Sam I was easy reached N/F 0,4 dB. Than I have changed C1 - original value 2,7 pF to 2,1pF ATC http://www.atceramics.com/ with http://www.atceramics.com/products/700a.asp . Also out pin from SMA connector have to be as short as possible. Than I had also changed L2 to 2 turns on diameter 2,5mm with wire CuL diameter 0,28mm and L1 is original 3,5 turn on 2,5mm diameter and CuL wire 0,28mm, only position of L1 is different, see picture below. Than I slowly moved trimmer for -G1 voltages and with combination of moving of L1 I set up showed parameters. Easy was possible to reach 0,2 dB and after more time playing with L1 I reached 0,15dB N/F. Gain is not so high as was with 0,4dB N/F - 38 dB but N/F is more important parameter for my EME use. Used units are showed below and temperature in my lab was in the time of experiment 21°C. I will take this VLNA for measuring also to Martelsham 2009 comparing results with other noise source.
Sam congrats to your construction, very well done !!!!!
My N/F measuring equipment HP8970A showing after couple of small changeovers this result 1296 MHz - 34,25 dB gain and 0,15 dB N/F
New Noise source head from NOISE COM Inc NC346C 0,01 - 26,5 GHz
As looks coil for powering of source and input coil now
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