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
conductivity ground is available."
The method of operation proposed is that there is a degree of tilt of (1 to
4 degrees depending on ground type) to the wavefront passing over ground so
that there is a horisontal component which will produce an induced emf in
the wire.
If I read the explanation right, the degree of tilt is greater over poor
conductivity ground, and this gives 4 times as much emf as over good ground.
I don't see that 300m of wire can really be referred to as a Beverage,
representing only about 1/7th of a wavelength.
73
Hugh M0WYE
----- Original Message -----
From: "Alan Melia" <[email protected]>
To: <[email protected]>
Sent: Thursday, September 11, 2003 11:16 AM
Subject: LF: Re: re EWE aerials
Hi Mike, that is an interesting philosophical / technical point....what is
the length of a Beverage ?? they obviously work better if they are longer,
and the aerial has more "coupling" to the wave front....maybe more time to
integrate the energy in the wavefront.....but does that make a short (less
than a wavelength) travelling-wave aerial not a Beverage?? I tried to
relate
these type of aerials to the terminated directional coupler loops used in
coax and waveguide....but the "direction" seemed to be the wrong way
round.....I never quite understood why.
This leads on to the oft quoted ground aerials....where an insulated wire
is
laid along the ground or buried in a shallow trench. Reading the history
and
comments by Beverage would suggest that the reason for using this
configuration was the "low-pass" effect it produced. In the days when
selectivity was relatively poor, and there was a lot of noise at higher
frequencies, the ground aerial did not respond to the higher frequencies.
Then being generally laid on poor ground that VLF signals could easily
penetrate, even a zero altitude aerial had some "effective height". This
suggests that the aerial would be "relatively poor" at 136kHz, though I
certainly pick up a substantial signal on my counterpoise wire when I use
it
as an aerial. It is obviously a lot cheaper to lay a wire on the ground
that
support it for several kilometres on poles. No doubt this was an important
factor in the early competitive period of radio.
Cheers de Alan G3NYK
[email protected]
----- Original Message -----
From: "Mike Dennison" <[email protected]>
To: <[email protected]>
Sent: 11 September 2003 09:42
Subject: LF: re EWE aerials
> On 10 Sep 2003 at 21:11, Alan Melia wrote:
>
> > Finbar has also had reasonable success
> > with a form of Beverage (no, not Jameson's) 900 feet long run about 5
foot
> > in the air down the beach. It only worked in some directions, which is
odd
> > because a Beverage is not supposed to work at all over good ground
(like
> > sea-water).
>
> Ah, but at less than one-sixth of a -wavelength long it wasn't really a
Beverage, was it?
>
> Mike, G3XDV
> ==========
>
>
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