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Re: LF: RE: DLF passive received with earth antenna

from [Stefan Schäfer] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: RE: DLF passive received with earth antenna
From: Stefan Schäfer <[email protected]>
Date: Thu, 22 Jul 2010 18:44:05 +0200
In-reply-to: <[email protected]>
References: <[email protected]> <[email protected]> <[email protected]> <BF4A524700075746A6467658DFC7102C51094D0E37@ICTS-S-EXC2-CA.luna.kuleuven.be> <[email protected]> <BF4A524700075746A6467658DFC7102C51094D0E44@ICTS-S-EXC2-CA.luna.kuleuven.be> <263121BD51374246B3F184A43B2E9619@JimPC> <BF4A524700075746A6467658DFC7102C51094D0E45@ICTS-S-EXC2-CA.luna.kuleuven.be> <[email protected]> <E21763BAE3DF42FAA9E57979CFC3F5CD@JimPC> <[email protected]> <[email protected]> <[email protected]> <[email protected]>
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Dear VLF interested OMs,
This mail is written with dirty hands out of my car, now in 520m ASL. Raindrops are falling on the car roof and i am listening the CW-beacon "HDL" at 426 kHz (AM mode) in my IC706MK2G...
I just increased the earth antenna length to 700m! The distance betweens the earth electrodes is now about 580m. This will be the final length of my antenna unless i can't reach Michael Oexner in ~50km in some weeks.
Here in Heidelberg it rained several hours in the afternoon but i was fascinated to hang up the wire anyway. Now i am fascinated by the QRN impulses that are well audible in AM mode in the 706. There is a real fascinating component when listening AM. I prefer it to all the digital modes ;-)
Just befor some minutes i checked the signal level of DHO38. Indeed, measured with 3 Hz FFT the level has now increased to -12dB (averaged over some pixels my me), so a gain of 8 dB! Maybe it will even be better when the upper layer of the soil gets dry again! Attached you find some screenshots. Note the bad S/N due to the high QRN! I think there starts some IM due to the very strong signal of DLF (500kW at 153 kHz in 40km dist).
Like in my last test (below) i measured the signal levels of some transmitters on LF/VLF. Maybe there is a difference not just due to the antenna changes and WX but also due to the time (propagation) but anyway. Settings on the 706 like in the last test: 

DCF39: S7
129 kHz: s9+20 dB
137,7: S0, QRN up to S5
DCF77: S8
75 kHz: RST 509
60 kHz: RST 309 QSB
36 kHz: RST 209
425 kHz: S9+20 in AM mode
153 kHz: DLF carrier S9+40 dB, AM mode: S9+50 dB (compared to the last test, DLF transmitted 500kW during the measurement) 

additional:
580 kHz AM S9+60dB
1140 kHz AM (US BCD stn) S9+60dB
7250 kHz AM S9+60dB
All this seems very promising and i hope for some more distanced reception with the new antenna. Later, i will test it as a loop and/or long wire for 137 kHz... 

VY 73, Stefan/DK7FC/m



Am 17.07.2010 00:19, schrieb Stefan Schäfer:
Additionally i tried what happens when i connect the earth antenna directly to my IC706MK2G, without any matching and resonating. The RX was set to CW mode with the noise blanker and without the preamp and a 250 Hz CW filter. 
Some results:
DCFG39: S7
129 kHz: S9+10 dB
137.7 kHz: S0, little noise audible
DCF77: S6
75 kHz: RST 409
60 kHz: RST 309
36 kHz: RST 409
425 kHz: ("HDL") RST 559
153 kHz: (DLF carrier) S9+20 dB AM mode: S9+30 dB (after 18 UTC DLF transmits with 250 kW in 40 km distance)
Since the 706 is rather not one of the top class RX and there is no matching of the antenna these results are not to bad i find.
Maybe Horst Stöcker can do some similar RX tests? Would be interesting to see a difference.
Today i prepared 400m wire and tomorrow i will increase the length of the earth antenna by some 100m ;-) About 600m should be the maximum length to form the first half of a dipole for 137 kHz so the rest will be attached on the other end... 

73, Stefan/DK7FC
PS: If David Gibson is right when he says that a earth antenna acts not like a single turn loop there should be some RX results out of a direction of the minimum of a loop. The should be more RX stations in a radius of some Lambda ;-)

Attachment: DHO38_91,5mHz,10s per pixel.jpg
Description: JPEG image

Attachment: DHO38_3Hz_1s per pixel.jpg
Description: JPEG image

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