RadioBanter - View Single Post

August 24th 04, 01:54 AM

On 23 Aug 2004 22:32:00 GMT, oUsama (Yuri Blanarovich)
wrote:
I had the problem with statement "the wire below the Beverage is the wire
couples to the lossy media below it so well it becomes very
lossy" as far as I know wire maintains it's conductivity regardless where it is
laid.

Hi Yuri,

In fact, no one has said otherwise. It follows of common sense unless
ground were exceptionally conductive such that its magnetic field were
to compress the skin-effect layer of the wire. If that were so, it
would be a new world for us all.

Perhaps more accurate statement would be that wire laying on the ground
becomes less significant in its contribution to the performance of the above
Beverage.

Quite so - if demonstrable.

To find out the reality, the exact systems should be compared in various
situations. Modeling might not provide fool proof answers due to some programs
having hard time to model reality, that can be confused by varying ground
characteristics along the Beverage.

C'mon now, with only two or three wires involved? The only problem
modeling programs have difficulty with are with modelers.

I compared two such designs. Nothing very involved with a 3M high
100M long Beverage operating in the 80M band (perhaps not long enough,
I will let others do their best if they find fault). I then compared
it with another which had a wire running below it 1cM above ground
level. The two showed more than 8dB difference with the ground wire
model clearly lossier (EZNEC declared at that same 8dB).

Now, I know that such antennas are not designed to be transmit
antennas (and again, perhaps too short to boot); so I will leave that
to others to engage as a receive antenna if they doubt reciprocity (or
I will do that later this eve for them as I often have to).

Yuri, the problem with you arguing Tom's position is that nothing is
said of this glaring difference. It is quite remarkable (or I made
some remarkable mistake or the wire is just too short as I mentioned)
and it DOES denote a dramatic departure from accepted Beverage
characteristics which has been undisclosed as a comment from Tom, if
in fact he offered it. This 8dB loss does make sense in that you have
a leaky transmission line in a death embrace with ground. The wires
would split the power and the lower power contribution would certainly
attempt to warm the worms with more gusto.
[ IF perhaps we were to employ the old twinlead twist every foot or
so, we might find things evened out ;-) ]

I will let that simmer for this evening.

73's
Richard Clark, KB7QHC