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[TowerTalk] V-beam Gain and R+/-jX

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Subject: [TowerTalk] V-beam Gain and R+/-jX
From: (Jim Reid)
Date: Thu, 17 Jul 1997 13:36:34 -1000
Hi again to those interested in the topic;
and again,  thank you for your comments and advice.

Ok,  will stop optimizing for VSWR.  Decided,  since
Lloyd Colvin's V's did so well at 584 foot legs,  all
spaced 45 degrees,  that I would run that through AO.

Don't know how he came up with 584 foot length back in the
middle 50's,  but it models well.  Per AO,  these are the
results of Lloyd's array:

Freq    3.510   3.795   7.005   14.005  14.195  18.110  21.015  28.050

Gain,   6.4     7.14    10.4    8.9     8.9     10.5    9.9     9.9  dBi

Zr      283     165     176     522     2985    414     405     865  ohms

Zi      -j1144  j69     -j371   j752    -j1073  j534    -j872   j869  ohms

SWR     12.4    2.8     4.46    4.19    7.51    3.23    6       4.14 :1
@450 ref

Per Lloyd's Aug '56 QST article,  he was very pleased with the
array:  he netted 171 countries across the bands (course, he
didn't have 18 mHz band then) in one year; probably during
1955;  1954 was the year of Sunspot minimum,  and 55 appears
to be just about as 1997 is turning out to be.  Lloyd
was in Germany at the time (Signal Corp) and signing DL4ZC,
so he did have a lot of countries near by,  unlike the situation
out here near mid-Pacific. Wonder how he did as the sunspots went
on to a huge peak thru about 1959.

He fed his switched array via a tuner (type not stated,  but was
balanced tuner) and then he used 600 ohm balanced line to go up
to the relay switch box,  which he made up using a refrigerator
plastic food storage box and a couple of 115vac antenna relays.

So,  I will pull across as long a wire legs as I can to trees
at close to equal angles around 40 to 45 degrees apart.  Per AO,
one does not loose too much should the V legs not be even exactly
equal.  As Lloyd had no trouble matching with his tuner,  and
as several of you suggested that I should have no trouble with
the Johnson "big" matchbox,  will no longer be concerned about
that issue (can always vary the feed line length a bit if
necessary to bring the terminal Z down to a Matchbox useable

Thanks again,  and the trades are supposed to weaken by 
Saturday,  so maybe more can get done.

73,  Jim, KH7M  

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