[linrad] IM2 in RXHFA

[Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxx>]

Hi All,

The first production RXHFA unit has arrived here (much later than 
anticipated)

When checking it I found I have made a mistake in the layout of the
input switches that are used to select the appropriate band pass 
filter for the desired frequency band.

These switches use J310 and as it turns out stray capacitances
from gate to ground degrade IP2 seriously. This problem is
corrected by mounting the gate resistors in the air close to
the transistors rather than on the PCB. 

For details, look here:
http://antennspecialisten.se/~sm5bsz/linuxdsp/rxhfa/imd2_hfa.htm


73

Leif / SM5BSZ


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