Stefan,
Thank you for the information. I was hoping for input from you and Uwe on ERP and antenna angle, and your information is very helpful.
Regarding antenna angle:
I am hoping to detect T/A VLF signals, and a long integration time is important. Without special integration algorithms, changes in phase of the received signal limit maximum integration time. Even at T/A distances, low antenna angles (angles far from vertical) can increase the sensitivity of phase to day/night transitions and other environmental/ionospheric factors, and thus limit maximum useful integration time. All of the above is for a constant non-vertical antenna angle; maximum useful integration time is even less when the antenna angle varies.
I don’t have solid numbers for phase vs. antenna angle, orientation and distance yet (the phase variations of interest are of multimodal origin, so multimodal analysis is required), but the information that you provided will help very much in converging to an estimate of maximum useful integration time with conventional integration algorithms.
For T/A VLF signal capture planning purposes, do you think that it would be safe to say that, in the next year or so, most amateur antennas long enough for potential T/A VLF communication will either be nearly horizontal (fixed at both ends), or fixed at one end with a variation in angles as in the example that you gave below? If so I will plan for something to assess, manage and possibly improve maximum integration time for the phase variations expectable from such antennas.
Thank you for the information that you provided and all of your remarkable contributions to VLF and LF.
73, Jim AA5BW
Hello Jim,
Am 27.12.2013 00:10, schrieb hvanesce:
Would 500W into a 300m antenna imply approximately 10mW < ERP < 50mW after coil losses, at 9kHz?
I assume that question is directed to me?
In these experiments i got up to 58mW ERP. A rough calculation of course. It depends on the angle of the kite, which can vary from 80 deg to 40 deg. The average on a windy day is something arround 65 deg.
But for a 300m vertical you will need a special permission in Germany and the air traffic control must be informed 48 hours in advance (giving out a NOTAM). So that was quite an effort. But most exciting! :-) My special permission expired some years ago.
Now the signal is 20 dB weaker, or must be 100x slower. But here i have mains power and don't need wind any more..
73, Stefan/DK7FC
Does your antenna orientation and elevation angle vary? (my maximum integration time is dependent on phase rate of change which is dependent on the antenna angle, even if the antenna angle is constant)
I enjoyed seeing the strong signals earlier this week on DK7FC, PA1SDB and other grabbers, thanks!
73, Jim AA5BW
From: [email protected] [mailto:[email protected]] On Behalf Of [email protected]
Sent: Thursday, December 26, 2013 2:53 PM
To: [email protected]
Subject: Re: Re: VLF: 8969.99
Hi Stefan and Eddy,
thanks for the reports. the equipment here is the same as ever (500W output into 300m aerial wire).
Markus asked for some OPERA OP4H tests. We have to schedule that test.
GL
Uwe/dj8wx as Tom dj8CAT.
Von: [email protected]
Gesendet: 26.12.2013 13:55
An: [email protected]
Betreff: Re: VLF: 8969.99
Hi Uwe, Tom, VLF,
Best signal ever from Tom, capture attached. Is it due to the propagation or did it improve your signal?
What about some tests in OPDS32 or maybe JT9-30? Unfortunately there is permanent rain here so i have to wait some days longer.
73, Stefan/DK7FC
Am 26.12.2013 10:58, schrieb g3zjo:
Hi All
Yes, yesterday was quieter on 8.9KHz with less catastrophic noise pulses. This meant that although Uwe's signal was less strong than during other tests I was in the catchment area. The low signal level means there are breaks in the line here in both 424uH and 47uHz FFT but I was able to catch some nice periods when the signal in 47uHz was10dB above the noise peaks. I can categorically confirm reception.
Thanks Uwe and (Tom DL8CAT) for the signal.
73 Eddie G3ZJO
http://www.g3zjo.talktalk.net/vlfgrabber.htm
