Hi Hugh, thanks for that I don't have that book but that is what I have
"believed" to be a Beverage. However being cantankerous ( as a G3 I am
entitled to that condition ;-)) ) It occured to me that like your book a
lot of these text-books are simply repeating the content of older tomes, and
possibly perpetuating some myths. It does not say why the aerial has to be
longer than a wavelength....is it just the case that it needs that length to
really show the effects? I can see this in directionality as longer aerials
have narrower main lobes. But I would have thought that a travelling wave
aerial should work (to some extent) whatever its length since it is
aperiodic, may be the longer it is the bigger the "aperture" hence the
bigger the signal-voltage at the terminals. In fact a lot of us pick up
very big signals with aerials at 10m which are less than 100m long. I really
wonder whether anyone has done proper measurements....it is obviously
difficult. I must try and contact a ex-BT wireless man who was involved in
long-distance short-waves before the war.
Terman (1943) for instance refers to it as being between half and several
wavelengths long. He also quotes a height of 10 or 20 feet. I guess to show
directionality it would need to produce a much great voltage from the
travelling wave effect than from its low effective height as a top loaded
vertical (which would be almost omni-directional) Terman does quote a couple
of references from 1923/4 and these might be worth me ferreting out.
Another though is that since the aerial is so critically dependent upon the
slowing of the phase-front, the use of insulated wire may well nullify the
effect, by causing the velocity in the wire to be much less than that of the
wavefront.
Now, anybody got a spare 20 miles or so of old telephone pole-line in the
middle of a desert??
Cheers de Alan G3NYK
[email protected]
----- Original Message -----
From: "Hugh M0WYE" <[email protected]>
To: <[email protected]>
Sent: 11 September 2003 12:57
Subject: LF: Re: Re: re EWE aerials
Alan, et Group,
The Services Textbook of Radio (1958) Volume 5, (page 336) says that "a
Beverage, or wave aerial, is a straight wire several wavelengths long,
usually carried by insulators on telephone poles at about 30 feet above
the
ground..."
Further on it says "Such aerials should be at least one wavelength long,
so
that for the very low frequencies involved, several miles of line are
required. They are therefore only suitable when a large area of poor
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