A few replies are inline.
Chuck
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: "CHARLES HUTTON" <charlesh3@msn.com>; <ford@cmgate.com>;
<topband@contesting.com>
Sent: Friday, August 20, 2004 4:47 PM
Subject: Re: Topband: Two Wire Beverage Query...
> > I'd say that given "average" elevation angles for DX, you
> should treat both
> > arrival elevation angle and tilt from ground loss as being
> roughly equal
> > factors.
>
> None of that matters anyway Chuck when the pattern of the
> antenna isn't any good. We know a lot more about antenna
> patterns and how antennas respond over earth than we did
> back in the earlier part of the 20th century.
CH: Then why do all the measured plots from the massive Litva and Rook 1976
report and all the Rome AFB data from the 70's all show patterns that match
what I said? Do you have references to measured, published data that we can
look at? Sure, we "know more", but can you be more specific?
>
> The fact is we want the horizontal area of the antenna to
> have as much response as possible. If we put a wire below
> the antenna that *really* changed things we know by where it
> is located it could only make things worse.
Not sure why you replied to me with this - I posted nothing about adding a
wire.
>
> A Beverage responds in the horizontal area only because of
> the high loss in the media below the antenna. Without a
> highly conductive media below the antenna, it's a cloverleaf
> with a null off the ends caused by the vertical ends
> dominating the response.
> It's all in the antenna pattern. We can have all the tilted
> wave we like but if the antenna has a zero response slice
> looking at it and major lobes 20dB stronger 45 degrees to
> either and off both ends, we won't be very happy with the
> results.
A Beverage is incapable of discriminating between wavefront tilt caused by
local ground losses and tilt caused by azimuthal arrival angle from
ionospheric propagation. A horizontal gradient is a horizontal gradient.
That's certainly a basic tenet in any text on travelling wave antennas that
I have ever seen, and have never seen anything saying that it responds only
due to lossy ground.
>
> The only thing that prevents people from shooting themselves
> in the foot with the wire below the Beverage is the wire
> couples to the lossy media below it so well it becomes very
> lossy, and of course that means it doesn't help with
> stability or termination.
>
> If you think it does, lay a very long wire on the ground and
> measure the input impedance. See how it looks compared to a
> ~50 ohm ground rod connection....I guarantee it won't look
> pretty.
Again, I wrote nothing about a wire under the Beverage.
Chuck
>
> 73 Tom
>
>
>
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