Message-ID: <5.0.2.1.2.20011004082609.00a1f080@mail.pncl.co.uk>
Date: Thu, 04 Oct 2001 09:51:29 +0100
To: rsgb_lf_group@blacksheep.org
From: "Walter Blanchard" <blanch@pncl.co.uk>
Subject: LF: Big/small antennas
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This big/small antenna business :<br>
<br>
Let's get this straight - what matters is RADIATED power not how big the
antenna is.&nbsp; Radiated power is the ONLY determinant of how far we
get . An antenna is only a launching device for em energy and as long as
it is capable of launching whatever power we think we need that is all
that matters.&nbsp; Its efficiency is irrelevant if we don't mind how big
our electricity bills are and we are able to control the lost energy
properly.&nbsp; One watt from a tiny antenna will get across the Atlantic
just as easily as one watt from a huge one.&nbsp; The big difference is
how easy it is to produce that one watt.<br>
<br>
Something of a legend has grown up in the amateur community that you need
a huge antenna to get anywhere. This originated in the old licensing regs
that put a lid on the&nbsp; DC power you were allowed to use in the final
amplifier<i>.</i>&nbsp; It was easy to measure and when we had inspectors
running around they could check it quickly and simply. This put a premium
on final amplifier and antenna RF efficiency and&nbsp; a &quot;big&quot;
antenna, at any frequency, was the best way of obtaining maximum
ERP.&nbsp; Hence the big DX names with multi-multi-element HF arrays
hundreds of feet in the air. Now the limit is on <i>radiated</i> power
which is much harder to measure (see almost any posting on this reflector
for the past few years) but gives us the freedom to use any final
amplifier power we like to make up for antenna inefficiency.&nbsp;&nbsp;
So if it takes a 100 kW amplifier who cares?&nbsp; As long, of course, we
can control all the flashovers, corona, arcing, melting insulators etc.
<br>
<br>
To say that a &quot;big&quot; antenna is necessarily better than a
&quot;small&quot; one is therefore rubbish. It's only true if you're a
professional wanting 100% reliability under all conditions; are prepared
to go into mechanical engineering in a big way; pay lots of money and
have vast amounts of real estate. Some are, but it's hardly
&quot;amateur&quot; radio and what exactly does it prove anyway?&nbsp;
Only what the professionals have known for many years.&nbsp; Far better
to play about with Micky Mouse antennas that no self-respecting
professional would dream of using and get an occasional DX contact.<br>
<br>
Final word - the ERP rule is of course open to considerable abuse. The
field strength figures produced recently on this reflector seem to
indicate that considerably more than 1 watt is being radiated by some
people.&nbsp; Have they got a special licence like the one we got for
Puckeridge?<br>
<br>
Walter G3JKV.<br>
<br>
&nbsp;<br>
&nbsp;&nbsp;&nbsp; <br>
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