[amsat-bb] 13cm pre-amp problems

["William Leijenaar" <pe1rah@xxxxxxxxxxx>]

Hi AMSATs,

Because I can not here AO40 with the NORSAT convertor alone, I decided to 
make some pre amplifier. I decided to make the pre-amp that is published in 
the ARRL "UHF/Microwave Project Manual Volume 1" ,
on page 7-8. This design is made by WA8NLC and looks very good.

I made an copy of the lay-out and made it on teflon PCB as described.

Altough this has to be an pre-amp, it is more like an 13cm oscillator.
When I put my finger on the input microstrip-line the oscillation is gone 
and the ampliefier seems to work very good. The problem is that I tried many 
things to get ride of the oscillation, but I can not stop it.

The option that worked a little, was putting an 100E resistor at the input 
to ground. This is not the option ofcourse, and oscillation comes back over 
an longer period of time.

I have tried another FET, carbon foam, other Rsource to get other drain 
current, other L1&L2.... nothing works.

The thing where I now think of is the box where I soldered the PCB in.
Maybe it is the best size for resonance, but I really doubt it. Before I 
will de-solder the fragile PCB out of the box, I will first ask for some 
other sugestions.

73 de PE1RAH, William
pe1rah@hotmail.com



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