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LF: Re: activety/stationlist

To: [email protected]
Subject: LF: Re: activety/stationlist
From: "James Moritz" <[email protected]>
Date: Sun, 21 Mar 2004 13:03:54 -0000
References: <[email protected]> <[email protected]> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Dear Dick, LF Group,

What interests me is to know who's active and with what power and antenna.
I wonder is there is any list which contains that info.
I know for example that such lists where quite common in the EME
(moonbounce) scene.

Maybe it gives a better picture of what would be a reasonable set up to
start with.
Ahh, if only... The Effective Radiated Power is the best measure of the
transmission capability of a station on LF. But it is not a simple matter to
give a meaningful figure for ERP, since as well as TX power and antenna
cofiguration, the radiated power depends a lot on the losses in the antenna
and its surroundings, and also the environment around the antenna. The
efficiency of "back garden" amateur antennas is normally < 0.1%, but varies
a lot. An antenna in an urban area can have several dB less ERP than the
identical antenna in an open field. For a comprehensive discussion and
calculations, see Rik's web pages on http://www.qsl.net/on7yd/136ant.htm. So
attempting to give a meaningful ERP for a station is not easy.

The only real way to get an accurate measure of ERP is from field strength
measurements - through a long series of measurements, I found the ERP of my
station was about 400mW using my normal 10m high inverted L antenna and
1200W RF. After dark, when the neighbors can't see, I put a fibreglass mast
under the centre of the antenna span to turn it into an inverted V
configuration that is 14m high at the apex. This increases the ERP to 1W
almost exactly. Even so, changing weather conditions cause a significant
change in ERP due to changing antenna losses - the ERP may be 3dB lower in
wet weather compared to dry, very cold weather. So the signal coming from my
QTH can vary several dB even when using the same TX power.

I believe UA licence conditions limit TX power to 100W on LF - but Ed has
always done a good job in finding very big antennas - eg. 80m high for the
current expedition. For antennas this big, efficiencies of a few percent
should be achieved quite easily, giving UA0LE maybe 10W ERP, even though
using a relatively low power. Most of Europe seems to be limited to 1W ERP
maximum, and this is quite hard to reach in practice, which is probably why
Ed's expeditions put out such good signals.

Cheers, Jim Moritz
73 de M0BMU





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