Hello Jim, Piotr, Alex, Markus, Chris, Mike, LF :-)
Thanks all to this interesting observations and your reports about the
LF ferrite antennas and propagated signals. I'm sure there will be more
useful nights for such tests, anyway the tests have been successful,
very happy about that.
If QRSS-60 is possible with O copy in such conds, CW should be possible
on a quiet sunday morning. Maybe we can test that later :-)
Piotr, congrats to your successful reception. The QRM is stronger at
home but the signal levels as well, compared to the previous antenna. So
if you go outside with that ferrite antenna, you can easily gain 20 dB
S/N or so. Fascinating, 800 km distance with an indoor antenna during
QRN+QRM!! :-)
Looking forward to further tests!!
A few minutes ago, i improved my ferrite antenna a bit more: Have
replaced the fixed 2.2 nF cap by (1+1+0.15+0.033)nF + a variable 47pF
cap with an axis for hand adjustment + a switchable 47pF cap. This is
rather compact than a 500 pF variable cap and reduces the volume of
conductive materials near the ferrite rod. So this allows me now to
easily tune over the entire amateur LF band. Even more useful: If i tune
the variable cap to 137.7 kHz and just switch the fixed cap, i come out
at 136.5 kHz (CW!) without the need to further adjustments. Excellent,
isn't it? :-))
The high-Z preamp is still an open project but soon i have it completed.
What a fun!
73, Stefan/DK7FC
Am 26.08.2011 03:43, schrieb Piotr Mlynarski:
James Moritz pisze:
Dear Stefan, Markus, LF Group,
A screenshot of DK7FC and DF6NM received in IO91VR between 2230 and
0000utc, with 84mHz FFT resolution, and using the ferrite rod
antenna. DK7FC seems to be about 6dB stronger than DF6NM here, on
average. But not really a very good night for testing receive
antennas - the QRN level is so high that the proverbial piece of wet
string would be just as good!
Cheers, Jim Moritz
73 de M0BMU
Dear Markus, Stefan, Jim, LF
Maybe this night is not a very good one for testing different rx
antennae according to Jim observations , nevertheless, some of us
decided to do it ... :)
Enclosed, there is a SL capture from my night 'experiments' - at
first, i have used my air loop antenna ( 1 sq. meter, 11t ) About
2:25 a.m. local time I disconnected my air loop while SL was running
, then, i reconnected SDR-IQ to my ferrite-rod antenna which was
inside the room !!!
( i only managed to raise it some 40-50 cm above the floor) and to my
real amusement i could still copy Markus DF6NM, also Stefan, though i
got some constant qrm line almost
on Stefan.. 172 freq i did not play with brightness/contrast etc..
just to see how the noise changes.
Anyway, i am very happy - it is my first positive observation of a
distant amateur signal on 136 kHz band ( if i have correct data Stefan
grid-loc is JN49IK, Markus JN59NK so this makes
800 and 640 km , respectively) using ferrite rod antenna ( described
in earlier mails). As an amplifier i have used Roelof, PA0RDT
miniwhip circuit , simply
using as a high Z-input the LC parallel network.
73, Piotr, sq7mpj
qth: Lodz /jo91rs/
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