[CQ-Contest] Re: [TowerTalk] Antenna Height Optimum for Caribbean/South America

[T. A. Russell]

re: Antenna Height Optimum for Caribbean/South America?

Good Question Rod!  (N5HV  de  N4KG)

A Tribander at 35 to 40 ft will cover all of the higher angles
supported by the ionosphere, even during high sunspot activity,
assuming FLAT ground.  For sloping ground, even lower may be
warranted.  That is why I believe and recommend that everyone have a
low tribander if possible.  (For USA contests, my 40 ft TH7 is often
20 dB better than my 80 ft TH6 at distances of 600 to 900 miles due to
the pattern null of the higher ant!)

The situation from W4 to the Caribbean and Central America gets a
little tricky.  During mid-day, a high angle two hop mode works fine.
Later in the afternoon and early evening, the MUF drops, especially
during lower sunspot activity.  Under these conditions, the higher
angles are no longer supported and we must reach these closer in DX
stations in a single (LOW ANGLE) hop under 10 degrees while more
northern stations can still use 2 hops and lower antennas.
Eventually, the skip can lengthen to where we no longer hear the
Caribbean station (or only via backscatter) and a thundering pileup of
northern and western stations.

Interestingly, the MUF to Africa seems to stay higher for longer
periods of time and I usually park my 40 ft high TH7 due east.  This
same TH7 is often my best antenna to Europe, especially on 20 meters
in the afternoon. Late in the day, I turn my 80 ft high TH6 to South
America / Caribbean. (Higher would be even better for the late
afternoon/evening conditions to SA/CA/Carib. from W4)

Now that I have retired from competitive contesting, I guess it won't
hurt to let the cat out of the bag.  Put up those LOW tribanders now!
(Yes, my higher monobanders are usually better at night and for
opening and closing the bands.)

de  Tom  N4KG
............................

On Fri, 10 Oct 1997 21:32:27 -0500 w5hvv at aeneas.net (Rod Fitz-Randolph)
writes:
>I read with interest the e-mail message from Bill, W4AN, regarding
>tests performed with his entourage of 10 meter antennas.  I am about
>to put up a TH3 MKIII on the tower, attached permanently to the
>tower and pointed at the Caribbean and South America for my "Instant
>Point" antenna during the contest season.  I also have a KT-34A at
>72 feet and a TH7DXX at 132 feet.
>
>My question is: what height should I place the TH3 at for maximum
>performance from 1500 to 6000 miles to the South East?
>
>I had been thinking that 35 or 40 feet would be about right.  I have
>had the trees around the tower trimmed so that I could do that.  
>Before
>I put it up, though, I would like to hear from some of you that have
>an idea as to what height at which the antenna should be placed.
>
>Thank you.
>
>
>Rod, N5HV
>w5hvv at aeneas.net
>


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