Message-ID: <3855453F.152AF742@netscapeonline.co.uk>
Date: Mon, 13 Dec 1999 19:13:04 +0000
From: "malcolmg3kev" <malcolmg3kev@netscapeonline.co.uk>
Organization: Netscape Online member
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Lowfer's Net - sunday 12 december
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Re-A single ant to use on all bands. Don't do it, especially on VLF. Use a
single antenna for each band. It is difficult enough to get max efficiency on
136 using an antenna specifically built for the band, anything else is a
compromise and would result in poor and disappointing results. The same applies
to 160 metres. If you are serious about vlf achievements look for a small farm
in the country and large antennas.
Good insulators from marine/yacht outlets only cost 35 pence each. Why bother
about toothpicks, hard boiled eggs and shoe laces. A tooth brush would cost more

and melt down at about 11 watts when dry, and less when wet.
73 de Mal/G3KEV


john sexton wrote:

> Hi Dave, G3YXM,
>
> Just to finish our brief discussion yesterday on the Lowfer's Net, my reason
> for trying a transmitting loop first is so that I can operate on both HF and
> LF without having to put up two antennas.
>
> The problem is that the garden is rather short and so I have had to bend the
> ends of the G5RV downwards. The top is 64 feet and so each end descends 19
> feet. If I were to use the antenna as a top-loaded vertical, I would
> probably have to chop off these two descenders, which would probably ruin
> its low-angle radiation for HF. The ends come down to about 7 feet above
> ground and so it is easy to attach another 64 feet or so of wire a couple of
> feet above ground to complete the loop. It is then fed via the vertical
> feeder to the centre of the top. At the bottom of the feeder will be a
> water-proof box containing alternative matching to heavy gauge 50 ohm coax
> (Mr Westlakes best) for either HF or LF. To operate on HF, I would have to
> disconnect the lower part of the loop and switch to an HF balun. For LF
> reconnect the lower loop and switch to a Loop Tuning Unit as described in
> Steve Rawlings home page. He has kindly given me pointers to sources for
> components.
>
> Ideally the switching might be made using high voltage relays as in the
> article on Transmitting loops on page 2.25 of the LF Source Book, but
> initially I would do it manually.
>
> The principal problem I have found during initial tests, is that the DC
> resistance of 300 ohm feeder (best quality air spaced) is 0.7 Ohm for 34
> feet - very high! So I am making my own out of 50/.25 wire with 3inch
> spreaders, which will reduce it to about a tenth of this figure. By the way
> can anyone complete the graph of RF resistance against frequency from Les
> Moxon's book (HF antennas for all Locations fig 3.10) for the bit of
> interest between 1 MHz and 0Hz. The graphs are shown as straight lines, with
> the resistance increasing with decreasing frequency, but it must turn over
> at some point in order to come down to the DC resistance at 0Hz.
>
> This must be a problem others have faced, how to use a single antenna for
> both HF and LF - but I haven't seen any discussion about it.
>
> Nice to meet you on the air for the first time, all be it not on 136 yet,
> but I have heard you on that band many times, including twice on Sunday,
> when you were S8 here in Reading despite the fact that the RX loop is
> East-West at the moment.
>
> 73s
>
> John, G4CNN, IO91ML
>
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