Re: LF: Re: G3XBM - very long carrier VLF transmission test Dec 15th

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Dear Jim (and others),

Very many thanks for trying to detect my Dreamer's Band signal today. I was aware of 3 stations definitely looking within 70km of my QTH and, not surprisingly, not one was successful. I was hoping that a couple of stations in the 10-20km range might have been looking and possibly might have had marginal copy. As it was, only more distant stations were, to my knowledge, looking. It is still possible some further reports will be received. If anyone is interested I have a record of my transmission sequence/times between 0900 and 2200z. The transmitter has now been turned off.

I am most interested in the ERP calculation suggested by Marcus and will attempt to calculate the ERP for my present VLF system in the next few days. I suspect it will be <<1uW. With this data I expect someone here will be able to hazard a guess at what my far-field (radiated) range might theoretically be, although I suspect "not very far" field at all :-)

My next test (probably after Christmas and in better weather) will be some 8.76kHz transmissions using the elevated (in the air) loop rather than the earth electrodes to compare range. I would also like to do some more "forensics" to try to better understand just how my signals are getting out across the fens as well as they do locally and of course to find the absolute limit of range with earth mode conduction or whatever mode it is.

Thanks again - even negative results are results.

73s
Roger G3XBM

On 15 December 2010 22:10, James Moritz <james.moritz@btopenworld.com> wrote:

Dear Roger, LF Group,

I left the VLF RX set up on your stated frequency today, but no signals have been detected so far. There was a rather curious spectrogram trace close to your stated frequency - see attachment - but I assume this is local QRM, since it repeats every 31Hz or so over the nearby frequency range, and I have seen similar things here before a number of times.

Cheers, Jim Moritz
73 de M0BMU

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