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

[DK7FC <selberdenken@posteo.de>]

Hi Jim,

You can still find the single decodes in the WSPR database. Most of the reports were with the wire in loop configuration (ends grounded). This gave clearly better results! I switched to the dipole config yesterday 09.SEP. 17:38 UTC
Yes, 10 W RF out, at least in the loop config.

73, Stefan

Am 10.09.2018 16:35, schrieb hvanesce@comcast.net:

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: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK7FC
Sent: Monday, September 10, 2018 8:36 AM
To: rsgb_lf_group@blacksheep.org
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 hvanesce@comcast.net:

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: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Markus Vester
Sent: Saturday, September 8, 2018 5:53 PM
To: rsgb_lf_group@blacksheep.org
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 <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
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?
...