Yes just a wall of noise , now can see why Digital comms are
popular on 500 !
G. .
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From: "Stefan Schäfer" <[email protected]>
Sent: Thursday, June 21, 2012 12:19 AM
To: <[email protected]>
Subject: Re: LF: Test signal needed, observations...
Jan, Rik, MF,
I have made some measurements and observations:
When using the active E field antenna while having the transmit antenna in
resonance, the signal levels are 10 dB higher then with a de-resonated
antenna. So there is definitely a coupling between then. HOWEVER the S/N
is much better when the transmit antenna is out of resonance. This can
clearly be heared because i'm using a medium fast AGC now (USR file of my
last mail), so the lower audio levels become compensated. But the QRN is
very clearly louder than the background noise. So there is a receive
improvement (in this location) when the transmit antenna is out of
resonance! Now, the higher local QRM could be produced in the first amp
stage of the active antenna or is could come from the transmit antenna
itselfe. So i have connected the receiver to the transmit antenna and used
a switchable attenuator in series and set about to the same signal level.
The RX and netbook was running on batteries during the test. When
comparing these results (small active E field antenna versus large
transmit antenna) the S/N (e.g. of IQ2MI) of the small antenna is clearly
higher! In other words, the MF earth seems to be contaminated by QRM!
That means my receive sensitivity is another important step better than a
few days ago...
73, Stefan/DK7FC
Am 20.06.2012 02:17, schrieb pa3abk:
Stefan,
Just be sure that the TX antenna is not coupled to the E-probe. ( De-tune
the system when you check it)
I'm mostly listening on my TX antenna, the E-probe is only a few meters
away. These two interact in such that the E-probe is just a bufferamp of
the main aerial.
To give you an idea how heavy this is: With a portable (AWP20 AKAI) I
can enjoy MF in the toilet and bathroom providing the radio is near the
waterworks and TX aerial is tuned.
IQ2MI is "good" beacon, just before sunset it manifest itself here and
build up to S-6 during midnight. During the winter you can enjoy it the
whole day.
I
FYI sometimes during clubevenings (Tuesdays?) it comes "live" with CQ.
But assume they will not listen on 477 :-(
Checked Meteox, during our QSO a heavy thunderstorm was over your QTH, it
moved away and lost a lot of it's activity.
Just to advise you that you shouldn't misinterpret your observations.
Jan/pa3abk
NNNN
On 20-6-2012 1:29, Stefan Schäfer wrote:
MF,
I took the QRSS/CW beacon signal from IQ2MI as the test signal. It was
very well audible here, R5. It was interesting to see the deep QSB.
Both, my small active antenna and the transmit antenna show the same S/N
but maybe it would be useful to use a antenna switch to compare the S/N
without having a time delay (changing the antenna cables), due to the
QSB...
73s..
Am 20.06.2012 00:44, schrieb Stefan Schäfer:
Rik, MF,
Right now i'm testing the TX antenna as a RX antenna. This works much
better than expected. A 10 dB attenuator is needed but no problem.
Maybe you can give me a test signal again on 502 kHz, or someone else?
It looks like the QRN is much lower on that antenna. That means that
many of the crashes during my CQ calls have been charged rain drops
that were falling on the E field probe, just my guess.
I will listen another 20 min. on 502 kHz and apprechiate any test
signals from amateurs.
73, Stefan
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