Excellent Paul! Tnx for motivation ;-)
I know the LT1028 as the best audio op amp (available for noncommercial
customers) for such applications and have also built a narrow band LF preamp
with it. In comparison to the OP27 it gives 10...20dB more gain at 137kHz with
even less noise than 1nV/sqrt Hz.
PSE, what is your locator or the locator where your Rx antenna is placed? ;-)
What do you recommend to those, who just receive with a wire in the sound card?
I have thought about an active antenna, maybe with the BF862 wich gave vy gd
results on LF. Of course an isolating transformer for AF. And what about a
simple band pass filter to supress the 50Hz and it's harmonics? Necessary or
dispensable?
For 10 Euro i have bought an external USB soundcard that provides 30dB less
background noise! The input AF filter can be simply modified by changing some
SMD Ls and Cs.
Your RX system sounds professional. Except the mains ethernet that causes QRM
to other hams being active on HF!
What are your experiences about the needed distance between antenna wire and
the house and what about hight above ground? If one is using a simple wire,
which lenght is adequate? Is there principally the need for amplification or
can it just be reached by increasing the wire length? Sounds like simple
questions but maybe they aren't..
73 es tnx being QRV! :-)
Stefan/DK7FC
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