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?
...
