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Re: LF: Test signal needed, observations...

To: <[email protected]>
Subject: Re: LF: Test signal needed, observations...
From: "Graham" <[email protected]>
Date: Thu, 21 Jun 2012 00:28:17 +0100
Importance: Normal
In-reply-to: <[email protected]>
References: <[email protected]>,<[email protected]> <7E7DFBB4D102A04DB5ADC88D66628A4A0FAB195C@ICTS-S-MBX5.luna.kuleuven.be> <[email protected]> <[email protected]> <[email protected]> <[email protected]>
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Yes just a wall of noise , now can see why Digital comms are popular on 500 !

G. .

--------------------------------------------------
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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