Message-ID: <000c01c10ae4$3a405380$bba97ad5@default>
From: "Fred Rattray" <fred.rattray@btinternet.com>
To: rsgb_lf_group@blacksheep.org
References: <7D653C9C42F5D411A27C00508BF8803D55C54C@pdw-mail-r1.dstl.gov.uk>
Subject: Re: LF: LF/Hyper test
Date: Thu, 12 Jul 2001 15:05:48 -0000
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Andy

Would be interested to know how you get on with your NOV application for
9Khz.
Still have the remains of my old 2.4Khz Tx and Rx  and aerials that I used
to use for cave radio location work before moving to higher frequencies.

73
Fred
G4SPR


----- Original Message -----
From: "Andrew Talbot" <ACTALBOT@dstl.gov.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: 12 July 2001 10:06
Subject: RE: LF: LF/Hyper test


> The far field of a radiated signal, where the reactive E and
>  H fields can be safely ignored in propagation loss
>  measurements, occurs at approximately lambda / 2.pi
>
>  At this frequency, with a wavelength of 33.5km this occurs at
>  5.3km so you are still well within the near field.  Inside
>  this region the reactive E field falls off much faster than
>  1/R^2  and the magnetic field H even faster still, so the
>  decrease of 20dB going from R = 1.5 to 2.5km does not sound
>  too unreasonable.
>
>  As a point to work from, "Reference Data for Radio Engineers"
>  gives groundwave loss at 10kHz for a 100km path as 33dB.  The
>  curve does not go much below 30dB loss so can't read off
>  smaller distances, but if you assume 1/R^2 as a first
>  approximation for the radiated field (although not strictly
>  true for groundwave propagation) it should give some very
>  rough indications of what to expect from the 5km range by
>  extrapolating back from 100km
>
> The RSGB are still pursuing my 9kHz NOV application with the
>  authorities, eventually I hope to be joining in at these VLF
>  freqs one day !
>
>  Andy  G4JNT
>
>
>  > -----Original Message-----
>  > From: Rik Strobbe [mailto:rik.strobbe@fys.kuleuven.ac.be]
>  > Sent: 2001-07-12 10:42
>  > To: rsgb_lf_group@blacksheep.org
>  > Subject: Re: LF: LF/Hyper test
>  >
>  >
>  > At 09:02 12/07/01 +0100, DJ2LF wrote:
>  > >Some weeks before Markus DF6NM and me made some tests and
>  > found a max.
>  > audible
>  > >distance of 1500m and a max. visible distance of 2500m (on
>  screen of
>  > laptop).
>  > >Rec. antenna was 10m vertikal.
>  >
>  > Hello Walter,
>  >
>  > congrats on the 9kHz crossband QSO.
>  >
>  > Did you measure the current you could get into the antenna ?
>  > Ground-loss
>  > must be extreme at these frequencies.
>  >
> > It is interesting to note that the signal seems to be audible
>  > up to 1.5km
>  > and visible on screen up to 2.5km. If good software (argo,
>  spectogram
> > etc..) was used this would mean that the signal level
>  > decreased about 20dB
>  > between 1.5 and 2.5km !
> > Or otherwise it would mean that you would have to increase
>  > power from 12W
>
>
> --
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