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Hi Peter,
Further to your request for info/experience with
recievers ,I have tried several.The station here includes a 4 section BP
filter(PA0SE design)modified for 137.I hope that this keeps big signals out of
the front ends of my Rxs although DCF39 138.8 is a bit too close for comfort!
This filter is followed by about 12db of gain since my Loop and EWE type ants
have very low outputs.An emitter follower OP stage enables me to drive 2 or 3
Rxs.The main reciever is an old Icom IC781 which has 2 excellent 250Hz CW
filters.Gain is more than adequate on 137 and the spectrum display is useful for
keeping an eye on band noise but too wide for anything else.The 250Hz filters
are very good but sometimes too wide so I can switch in a NIR-12 DSP filter
which can go down to about 60Hz.There is very little ringing with this filter
but I would like to try the optimal design by PA0LQ. For monitoring the band and
for QRS and DFCW I use a Racal 1792.This an excellent reciever and I agree with
the comments by Andy G4JNT but although mine has 1Hz tuning steps,search tuning
is very difficult,so I leave it set to a fixed frequency and use Spectrogram or
Spectran to display the band or part of it as required.I have also tried an Icom
IC756 PRO which has very excellant digital filtering the 50Hz setting is quite
useable under all conditions even with high QRN.The display of filter width and
pass band tuning is very useful but again the spectrum display is not too useful
although somewhat narrower than the 781.The big problem with this Rx is that is
a bit deaf on 137 about 18db down on the old 781.
I hope these notes are of intrest.73s
Laurie..
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