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RE: LF: Re: 137 kHz WSPR-2 on a 900m long ground loop, this weekend

To: <[email protected]>
Subject: RE: LF: Re: 137 kHz WSPR-2 on a 900m long ground loop, this weekend
From: <[email protected]>
Date: Mon, 10 Sep 2018 10:35:47 -0400
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Hello Stefan,

 

Excellent results, and fascinating.

 

For the 13 WSPR reports below, is the antenna in dipole-on-ground mode (ends not grounded) or in earth-loop mode (ends grounded)?

 

Was the 10W that you mentioned the power-amplifier output power?

 

73,

 

Jim AA5BW

 

From: [email protected] [mailto:[email protected]] On Behalf Of DK7FC
Sent: Monday, September 10, 2018 8:36 AM
To: [email protected]
Subject: Re: LF: Re: 137 kHz WSPR-2 on a 900m long ground loop, this weekend

 

Hi LF,

The experiment is finished. Batteries are back charging.
These are the best reports:

Timestamp

Call

MHz

SNR

Drift

Grid

Pwr

Reporter

RGrid

km

az

 2018-09-09 03:30 

 DK7FC 

 0.137425 

 -27 

 0 

 JN39 

 1 

 SM3LNM 

 JP82qg 

 1559 

 20 

 2018-09-09 10:30 

 DK7FC 

 0.137425 

 -24 

 0 

 JN39 

 1 

 2E0ILY 

 IO82qv 

 767 

 303 

 2018-09-09 04:10 

 DK7FC 

 0.137425 

 -25 

 0 

 JN39 

 1 

 G3XDV 

 IO91vt 

 568 

 300 

 2018-09-08 12:20 

 DK7FC 

 0.137424 

 -16 

 0 

 JN39 

 1 

 DL4RAJ

 JN68kj 

 449 

 103 

 2018-09-09 10:20 

 DK7FC 

 0.137425 

 -7 

 0 

 JN39 

 1 

 DL0AO 

 JN59vk 

 349 

 89 

 2018-09-09 01:20 

 DK7FC 

 0.137426 

 -24 

 0 

 JN39 

 1 

 PA0RDT 

 JO11tm 

 327 

 315 

 2018-09-09 16:30 

 DK7FC 

 0.137425 

 -21 

 0 

 JN39 

 1 

 PI4THT 

 JO32kf 

 306 

 359 

 2018-09-09 07:30 

 DK7FC 

 0.137425 

 -6 

 0 

 JN39 

 1 

 DF6NM 

 JN59nj 

 301 

 90 

 2018-09-09 01:40 

 DK7FC 

 0.137429 

 -14 

 0 

 JN39 

 1 

 DC0DX/RF 

 JO31lk 

 218 

 0 

 2018-09-08 21:50 

 DK7FC 

 0.137424 

 -28

 0 

 JN39 

 1 

 DC5AL-R 

 JO31lk 

 218 

 0 

 2018-09-09 00:50 

 DK7FC 

 0.137425 

 -27 

 0 

 JN39 

 1 

 DF2JP 

 JO31hh 

 205 

 354 

 2018-09-09 07:50 

 DK7FC 

 0.137425 

 +1 

 0 

 JN39 

 1 

 DK7FC/HD 

 JN49ik 

 127 

 91 

 2018-09-09 09:50 

 DK7FC 

 0.137425 

 0 

 0 

 JN39 

 1 

 DL1GCD/1 

 JN48ar 

 115 

 136 


It was interesting to see the special characteristic for such an unconventional antenna. Another interesting thing was to learn about the different feed point impedances. I had no idea before...

Markus calculated 0.4 % efficiency for daytime in low distances, which is not bad at all. The actual distance to Markus is 230 km and with just 10 W it is possible to have a normal CW QSO!
But the night characteristics are not really favourable :-)

It would have been interesting to have someone receiving with a loop antenna, which could pick up the high angle radiation much better than an E field antenna, eventually.
There is so much to play with. It never ends :-)

73, Stefan


Am 10.09.2018 07:06, schrieb [email protected]:

Hello Markus and Stefan,

 

Markus mentioned:

“high angle radiation …possibly leading to deeper fading at intermediate ranges”

 

I would guess the same.

 

I checked the following to see if the 900m/137kHz configuration (> 1/4 wavelength freespace, >> 1/4 wavelength in earth), or some particular earth conductivity, or very-close-proximity to ground, or perhaps some hemispherical spreading in earth ground currents might reliably mitigate high-radiation-angle fading at intermediate ranges.

a) https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2005RS003298

b) https://nvlpubs.nist.gov/nistpubs/jres/64D/jresv64Dn1p27_A1b.pdf

c) “Characteristics of a Power Line Used as a VLF Antenna” (Dazey, Radio Science 1982)

 

Items (a, b and c) augmented a perspective that experiments are more reliable than theory in this realm.

I couldn’t find any basis in theory for ruling out high-radiation-angle fading at intermediate ranges, even with 900m/137kHz, and earth-loop and dipole-on-earth configurations, especially given some possibility of Eh+Ev nulls.

 

Perhaps more valuable than much of the theory is that the transmitter provided good far-field signals on first attempts at 1570 Hz, 1970 Hz, 2470 Hz, 2970 Hz and 137 kHz. That’s really something to think about.

 

73,

 

Jim AA5BW      

 

 

 

 

From: [email protected] [mailto:[email protected]] On Behalf Of Markus Vester
Sent: Saturday, September 8, 2018 5:53 PM
To: [email protected]
Subject: Re: LF: Re: 137 kHz WSPR-2 on a 900m long ground loop, this weekend

 

Hi Stefan,

indeed your signal has been very consistent around 5 uV/m and -8 to -10 dB in the afternoon. At 230 km range, this would indicate a radiated power around 40 mW (EMRP), or 0.4% antenna efficiency. Around nightfall, heavy QSB set in, with occaional minima where the signal fell below the decode threshold but was still ghastly visible in the waterfall with heavy RDF colour aberrations. I suspect that the diplole emits more high angle radiation than a vertical, possibly leading to deeper fading at intermediate ranges. 

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Sa, 8. Sept 2018 22:45
Betreff: Re: LF: Re: 137 kHz WSPR-2 on a 900m long ground loop, this weekend


Thanks to the many stations beeing RX-active on LF WSPR tonite.

It is very strange, the SNR reported by the stations below 500 km
distance was very good in daytime but now at night there are not more
stations receiving me, except 2 reports by 2E0ILY.
Also the software just reports JN39 instead of JN39WI.
Maybe some reports are not uploaded or shown on the database, because of
conflicting locators for the same callsign?
I can hardly imagine that nothing comes through at night. Very odd.
Does someone have an explanation what can cause these good results
during the day and such bad results at night?

73, Stefan

PS: My QRG is 137.425 kHz and starts each xx:x0 (each 10 minutes). Maybe
someone can see somethning on the waterfall display?
...

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