[amsat-bb] Journal 435MHz Pre-amp

[G0MRF@xxxxxxx]

Hello all.
 
A number of people on the reflector have bought kits of my  pre-amplifier 
design published in the Journal in Aug 2005.
 
The design was intended to give good performance at 435 and 1296MHz and the  
article showed a graph giving details of the performance to 1500MHz.
 
Thanks to some further testing by a UK constructor who is an RF  
professional, I now have some figures for gain and noise figure beyond  1500MHz.
 
 
Freq     NF      Gain
432      0.6      21
1296     0.48    20
1500     0.49    18
2000     0.64    14
2320     0.65    14
2500     0.66    12
2900     0.8      12.5
3000     0.78    12
3400     1.0      11
 
As you can see, the  performance is still quite useful at 13cms but is 
beginning to run out of gain  3400. On this particular example the coils were wound 
with an internal diameter  of 2.5mm and the NF at 432 is a little too high. 
2.7mm coils would improve the  performance by moving the cut-off down to 400MHz. 
 The best noise figure  was measured at 850MHz where is was a fraction below 
0.4dB. 
It was also observed that  cooling with a pletier device to 0 degrees 
centigrade improved the NF  performance by a further 0.05dB.
 
Regards
 
David   G0MRF
 
_www.g0mrf.freeserve.co.uk/432LNA.htm_ 
(http://www.g0mrf.freeserve.co.uk/432LNA.htm) 
----
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