Yes Markus,
By some calculations, Bob’s signal is close* to being detectable 24/7 at Todmorden and often during daylight at your QTH, for the next two weeks or so. A 24-hour opportunity in April is unlikely.
* with nominal propagation conditions, 4-hour integration, some tweaking and a large can of corona spray
You mentioned the more realistic prospect of particular daytime slots of opportunity, such as 15UT, and I agree that the chances are good now.
Daytime increase in attenuation now may be ~ 15db typical; in the summer, daytime increase in attenuation may be ~ 35dB typical. It would be difficult to guess April prospects for daytime detection/confirmation, but for planning purposes a reference point of at least 6dB additional daytime loss per month may not be unreasonable. One consideration is that terrestrial and ionospheric conditions could advance seasonal daytime-window closure without much warning; and that could be it for 29kHz daytime until fall/winter, but the window appears to be open now.
73, Jim AA5BW
I would think that the main difference between Todmorden and Nuernberg is that I'm into the sunrise dip an hour earlier. And my noise background is higher, so I tend to completely lose a weak signal which Paul would still receive well.
Anyway looking at the attached NAA plot I'm sort of perplexed by the strong propagation during the day. If Bob decided to transmit sometime around 15 UT, there's a good chance we'd pick it up.
Sent: Friday, March 07, 2014 8:57 PM
Subject: RE: LF: New OPERA OP/OPDS 2H tonight on 27.945 Dial Freq...
Bob and Markus,
Thanks, this seems consistent with the shape of the late-night/early-morning amplitude characteristic in the LWPC simulation (for 43N, 75W to Todmorden) that Paul sent to the group on March 1, 2014: a smooth, fast transition (and particularly with minimal multimode peak/null effects).
It’s interesting to note this characteristic (for this month, frequency and path), but more interesting to note consistency of Paul’s LWPC result with last-night’s data.
I don’t think that the difference in paths from Bob’s location to Todmorden and to Markus’ location should make much difference in the shape of the late-night/early-morning amplitude characteristic, but I could be wrong.
In another example of rough agreement between VLF models and test results in this group’s efforts (for roughly similar paths and times of year): the shape and magnitude of the phase characteristic measured by Paul (for 43N, 75W to Todmorden) overnight March 1st/2nd was consistent with a published model (Chilton 1964, based on empirical data) for a path of roughly similar land distance and water distance. The diurnal phase characteristic for paths of this length and orientation (43N, 75W to Todmorden) varies considerably month by month, so it was most interesting to see the close correspondence between Paul’s March 1st/2nd measurements and Chilton’s 1964 results for a different but analogous transatlantic path in early March.
73, Jim AA5BW
Markus;
I closed at 0820 as I saw the signal went away at about 0700 on the Markus grabber. Had to be up early so couldn't stay on longer. Will stay on longer tonite-Bob
From: [email protected]
To: [email protected]
Date: Fri, 7 Mar 2014 11:37:49 +0100
Subject: Re: LF: New OPERA OP/OPDS 2H tonight on 27.945 Dial Freq...
I dont really know when Bob switched off... On my grabber, the signal dropped sharply around 6 UT, thus the correlation peak was probably based on the first half of the sequence which ended 6:52. But on Paul's spectrogram http://abelian.org/vlf/sg29499.shtml the carrier stayed visible until after 8 UT.
Sent: Friday, March 07, 2014 9:28 AM
Subject: RE: LF: New OPERA OP/OPDS 2H tonight on 27.945 Dial Freq...
Markus,
This is a welcome sight. Thanks to you and Bob. Was this detection made approximately ten minutes before Bob switched off?
73, Jim AA5BW
Just one detection here, but that makes it worth the effort:
2014-03-07 06:52:02 WH1XBA 6448km 29499.000Hz 1mHz -52.9dBOp 100% 15.3dB
Out of the last four nights, this was the one with the highest noise. The carrier was visible since about 0:30, but the detection occured only in the morning when the noise went down before the signal did. Unlike Paul in Todmorden, I don't have a steerable pair of loops, so only the blanker to combat the statics.
Bob, thanks for this signal!
