Plot of variation of NAA diurnal amplitude for year 2013. http://abelian.org/vlf/tmp/naa_2013a.png Dark areas are where NAA was off. White areas are when my equipment was down. -- Paul Nicholson --
Hi Jim yes its a complicated subject.....but nice to kick ideas around......there is always something new to learn. Alan -- Original Message -- From: [email protected] hvanesce To: rsgb_lf_group@b
Jay, are these plots based on measurement or simulation? 73, Markus From: [email protected] Sent: Sunday, March 09, 2014 4:32 PM To: [email protected] Subject: Re: LF: Daytime 29.499 k
While not VLF, WWVB at 60 kHz shows no significant difference in signal level at various receiving locations summer vs. winter. http://www.w1vd.com/WWVBwintersummersig.jpg As expected though, SNR is
I'm plotting the signal in 20 minute integrations so there isn't much loss due to the phase change. We had about 120 deg phase change on the night of 6th/7th but it took 6 hours, not 2. Here I plot t
I'm pretty sure now this is a propagation change. Info from Bob via PM indicates that the antenna current is essentially constant during the transmission with negligible tuning adjustments. I can thi
Hi Jim I have been pondering those plots, but beware they are "relatve amplitude" I'm not quite sure what Paul means here but the big swings on a small signal v small swings on a big signal may not b
A better signal last night from WH2XBA/1 and I was able to go back to using 10 minute averages to improve time resolution http://abelian.org/vlf/tmp/29499_140310a.gif 120 deg phase change as usual bu
Paul, thanks for this work! carrier would be sqrt(2) times stronger than opera. I think the difference between 100% carrier and 50% keyed Opera is actually 6 dB, because the central spectral peak is
Thanks, you are right. My measurements are in a bandwidth wide enough only for the carrier component of the opera signal. Allowing for that, last night's test wasn't really any stronger than recent o
Paul, thanks very much, these are impressive plots. Some time ago Peter Schnoor had posted similar annual graphs for 75 kHz http://lf-radio.de/misc/hbg/chart_all.png and 135.43 kHz http://df3lp.de/mi
Yes Jim the 'z' scale is proportional to amplitude (flux density), not power. I completely agree with your interpretation of the plot - - The nighttime window doesn't quite close and even in high sum
Here is the background noise diurnal for 2013 at 29.5kHz http://abelian.org/vlf/tmp/29499_noise_2013.png The noise is averaged over a 500Hz band and converted to units of fT per root Hz. The noise is
I have no information. You would expect ground resistance to rise, but would that make noticeable difference to propagation if it is only a freezing of a shallow surface layer? I had to go to a narro
Thanks Jim for the detailed information. Bob and I had discussed the temperature effects in a private mail exchange, and hadn't quite come o the same conclusions. My take on the subject was that with
Reviewing Bob's direct mails, he mentioned a body of evidence of improved groundwave propagation at low temperatures and frost, based mostly on mediumwave broadcast experience. That seems to contradi
I think the propagation at 29.5 has changed, even though NAA looks normal at 24kHz. There's a new pattern to the phase change: a fairly rapid reduction of phase lead by about 120 deg during the first
I would have to ask how do you know what is actually "groundwave" It is extremely difficult to determine because at these frequencies there is return from the ionosphere at very short ranges. Also wh
