Harry,
I found your paper most interesting, including two of your observations in particular (I’ll mention the two observations in a separate message). I’m interested in VLF phenomenology for its own sake, and for its potential merit in DX. Your observations address some aspects of the near field regarding which useful data is scarce, and which I think could ultimately assist amateur VLF communications (wherein antennas are electrically small, and particularly influenced by near-field characteristics).
I wonder if the following would interest you:
I ran a number of 8.9kHz tests at ~100W PA out, taking calibrated signal-strength data at roughly logarithmically spaced TX-to-RX distances from ~ 1m to ~ 12km. I used loop antennas for these tests, with TX loop diameters from 1m to 70m, with horizontal and vertical orientation of the TX loop axes*, and one buried TX loop; and many (x, y, z) orientations of the RX loop antenna. I was unsuccessful in making measurements at 20km and beyond, in part because my RX bandwidth was at that time limited to ~10mHz min, and I did not employ impulse noise cancellation. The interesting part: while my antennas and local environment were considerably different from yours, I was surprised and very interested when reading your report, to see some correspondence in observations.
Would you be interested in the data from these tests? The data and notes are handwritten, but I have always intended to capture in Excel/Mathcad/Matlab form with tables and plots, and having seen your observations, I’m particularly interested in making 3D plots of the two characteristics to which I referred above, which include the infrastructure measurements** and max-range measurements.
If you’re interested, I’d be happy to post the data and plots next week (I’ll need to figure out how to post; a member of this group sent info on that so I will search for it).
Thanks also to Stefan and Eddie for facilitating the presentation and discussion of Harry’s findings.
* I did not orient the 70m diameter loop axis horizontally (i.e. I did not orient the plane of the loop vertically), but I can orient it at angles from vertical of up to ~ 45 degrees
** For example, at RX locations near streets, I occasionally measured the field angle and amplitude as a function of horizontal and vertical distance from the curb. Streets ranged from suburban to desert-mountain, and I was quite interested to see some correspondence between our measurements.
73, Jim AA5BW
From: [email protected] [mailto:[email protected]] On Behalf Of Harry Woodhouse
Sent: Saturday, April 19, 2014 1:40 AM
To: rsgb_lf_group
Subject: Re: LF: Ground Tests at 8.9KHz
Many thanks for your comments.
Harry G3MFW
On 18 April 2014 18:48, g3zjo <[email protected]> wrote:
On 18/04/2014 17:08, DK7FC wrote:
Thanks to Harry and you for sharing the link to this most intersting experiments. I've been reading it carefully. It motivates myselfe to think a bit more about VLF experiments :-)
Please forward him my compliments if the other adress is not his.
Hi Stefan
I am glad you appreciated the link and Harry's work. He will see your comments as he is a member of this Group.
My involvement came in after I suggested to Harry that he popped his write up on the cloud, he asked me to handle that as he was happier knocking rods into the ground.:-)
73 Eddie
