Graham and Bob, Attached plot shows loss over land or water at 74 kHz and (with some imagination) 136 kHz; probably best taken with a grain of salt, although the plot is associated with J. R. Wait’s analytic solution for field strength vs. distance, frequency and attenuation factor. Next message will contain a plot generated from Wait’s solution using the attached attenuation factors. 73, Jim AA5BW Definitely strange propagation on 75K ! Thats 6000kmt 3 hours with 'no' QSB ? other than a rise and fall , the gaps are most likely qrm dropping the decode level , to under the -44 point These 2 decodes , even with the 4/5 db scale misalignment , puts the signal ~ 10 dB over the previous max and round 15 dB over the first decode level .band appeared to be closed down ... by what ?? . double take though ? how is the s/n level computed ? Opera is the average over the time line , in this case , 65 mins 0230 -28 0.4 0.074615 0 WG2XRS/4 30
0245 -28 0.4 0.074615 0 <WG2XRS/4> FN12LQ 30 So how ? its the same Ae as 136 , but path losses ( over water ?) seem to be much less that 136 ? Sent: Wednesday, December 11, 2013 10:34 PM Subject: RE: LF: OP65 late start for tonight-73 dial as usual... Bob, Graham, Hartmut, Henny, all, It’s interesting to see these recurrences of Hartmut’s grabber showing stronger signals than grabbers closer to Bob (such as Henny’s grabber), at later times in the dark cycle. I second (third?) the motion that skip/multimode-interference is a likely contributor, especially considering the number of months over which this characteristic has been observed. Has anyone seen long-distance Hollingsworth plots for frequencies near 74kHz? I attached a Hollingsworth plot for 24kHz that supports the concept, but I have had little success finding such plots for LF [Davies (1990/2008) suggests that there isn’t much data of this sort for long-range LF]. I have a copyrighted plot from Bracewell (1951) that shows (at 85kHz) Hollingsworth-type signal strength cycles of ~6dB over range intervals of ~ 100km near 1Mm, and an analytical study by Johler and Berry (1964) showing (at 100kHz) Hollingsworth cycles out to 1.5Mm. These would seem to be qualitatively supportive of the skip/multimode explanation of signals stronger/later at Hartmut’s grabber, compared to grabbers closer to Bob (such as Henny’s grabber), but the east-RX/west-RX signal strength inversions observed in the 73kHz-band experiments by this group sometimes seem much larger than the ~6dB values in the two LF (85kHz and 100kHz) references that I have found. Congratulations to all on the 74.5kHz Opera results! 73, Jim AA5BW We need the local decodes from Wolf , they have the fade pattern plotted out , the web linked plots have the fade % but not the distribution Op is giving a calibrated precision s/n level average along the time line , so what your getting is accurate propagation data , you can recover it from the psk-map data base with a web sql search , or keep the Opera software running on a web linked PC and any band activity will be listed The total lack of signal in the Uk is not expected ! but last night , you could of dropped to 10% power , which , considering the wavelength , from the same Ae , starts to point to better prop than 136 ? odd , the path would support OP16 at that level as well at full power ! Sent: Wednesday, December 11, 2013 3:48 PM Subject: RE: LF: OP65 late start for tonight-73 dial as usual... G;
Take a look at Henny's capture and see earlier signal. Compare with Hartmut's capture that shows more signal later. All in all the band was good but varies as to when it peaks in a given area.
Hartmut and Henny and a few others have hot antennas and receivers. Hartmut uses a directional ant. Do some write-ups on these hot-shot blokes and there equipment. They have very serious 73 band equipment that really "cuts the mustard". Bob
From: [email protected]
To: [email protected]
Date: Wed, 11 Dec 2013 14:49:37 +0000
Subject: Re: LF: OP65 late start for tonight-73 dial as usual... This new fangled 75KHz stuff , Gary , its going strait over our heads .... Sent: Wednesday, December 11, 2013 2:10 PM Subject: Re: LF: OP65 late start for tonight-73 dial as usual... 3 LF Guys in the UK still no show , but Wolf , up to -35 dB , looks like the hat trick , 3 in a row .. -35 is a significant signal , at that level OP16 would decode , g4wgt/g0ktn/g8huh all have good LF set ups , -35 is 9 dB over the op65 level ... Skip distance ? , where is Alan when you need him hihi -36 | OPERA | 0.073 | 11/12/2013 02:22 | WG4XRS | FN12LQ | DL-SWL | JO52HP | -35 | OPERA | 0.073 | 11/12/2013 03:27 | WG4XRS | FN12LQ | DL-SWL | JO52HP | -41 | OPERA | 0.073 | 11/12/2013 04:33 | WG4XRS | FN12LQ | DL-SWL | JO52HP |
Sent: Tuesday, December 10, 2013 11:52 PM Subject: LF: OP65 late start for tonight-73 dial as usual... OP/OPDS65 tonight as promised and WSPR 15 tomorrow night. Thanks to W1VD and group for decodes to get me dialed in-should be interesting tomorrow night for first time on WSPR 15 on 73 band full night-73-Bob WG2XRS/4 [WG4XRS] NY No virus found in this message.
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No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4259 / Virus Database: 3658/6909 - Release Date: 12/10/13
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Attenuation vs Frequency - CommSystemsCh2.pdf
Description: Adobe PDF document
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