Hi Stefan,
You wrote:
...
However it does not work really well in the first attempt. The probes are
just 2 short wires from the resistors. If i come closer to one of them with
my hand i am getting some V (!) output signal from my own 136 kHz
transmission which take place in the moment.
> ...
O.K., that's how a well balanced amplifier should behave:
only the difference matters. So try using longer "legs" and
check for SNR and local interferences.
...
So far i have no TLE2426 on hand, so i used 2x 100 Ohm / 2W resistors and
47uF in parallel to each one to form a virtual ground. The AF transformer
you mentioned does not work on 137 and 475 kHz of course.
> ...
No, the transformers I'm using are performing well from 2 up to >300 kHz.
Available: http://www.oppermann-electronic.de/html/ubertrager.html
TDK 205 U, 4:1 instead of 2.5:1 as mentioned there.
Capacitive coupling <10 pF.
...
What is your final configuration and where did you connect the shield of
the CAT5 cable? Have you found any improvements on the schematic? Or is the
project lost in the junk box? :-)
...
The configuration did not change. I made some tests last weekend out in the
field. "Alpha" peaked up to 30dB SNR and I could hear insects landing
on one of the legs quite well. I'm using well shielded AF-cable not CAT-X.
Both shields are kept floating from "real earth".
OT: more and more strong echos now at 49749 kHz from Perseides.
Peter, df3lp
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