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

[Stefan Schäfer <schaefer@iup.uni-heidelberg.de>]

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 ;-)

DHO38_91,5mHz,10s per pixel.jpg
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DHO38_3Hz_1s per pixel.jpg
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