[TowerTalk] Takeoff angle-new perspective

[n4kg@juno.com]

N4KG response follows below.  Note the re-formating
that results when responding to word-wrapped text.
Truncating lines at 2/3 to 3/4 line length avoids this
reformatting problem.


On Wed, 20 Dec 2000  "Tom Hellem" <redpines@cybrzn.com> writes:
> Hi all:
> I have been following with interest the thread on takeoff angles, 
> etc. and
> there has been a host of very useful information. Bottom line seems 
> to be
> the more aluminum one can get into the air at many different 
> heights, the
> better. But one thing has become apparent to me- it has almost 
> wholly
> pertained to working DX and DX contesting. I would like to offer 
> another perspective.
> 
> I think a large percentage of hams have neither the pocketbook nor 
> the real
> estate to erect multiple towers and stacked yagis. Many of us have 
> to settle
> for one tower of modest height with a tribander, and we are pretty 
> much
> resigned to the fact that we are probably not going to make it into 
> the
> record books in CQWW. But, being of a somewhat competetive nature, 
> we think
> that we have at least a chance of making a showing in the stateside 
> contests
> like NAQP and SS.
> 
> So the question becomes this: What would be the optimum height for 
> say a 3
> element triband beam for stateside contesting use? Say up to a 
> maximum
> height of 70 feet or so, as that would be about tops for Rohn 25 
> with 2 sets
> of guys, and would be able to fit on an average sized lot.
> 
> I would be willing to bet there are thousands of us out here who 
> would be
> very interested to see some input on this question.
> 
> 73 to all.
> Tom K0SN
> Porterfield, WI
> 

An 80 ft high antenna places a NULL at typical 
mid-range skip distances for domenstic contests,
typically 800 to 1400 miles, depending on band.

High antennas ARE useful for backscatter, with
backscatter signals often peaking if both stations
point their antennas toward the SUN (a trick I 
learned from CD parties in the 1960's).

A 40 ft high antenna gives excellent coverage for
single hop F layer skip from 600 to 1200 miles or
more.

At 40 to 50 ft, a single tribander is the best solution.

At 60 to 80 or 90 ft, a high and low tribander make
a POWERFUL combination, even if they are not
phased.  With two tribanders, you get both 
directional and waveangle diversification.

Even a trapped dipole (CC D3, Mosley D.E., etc)
mounted on the side of a tower leg at 35 to 45 ft
will produce more signal than a higher tribander
at the NULL angle of the top mounted antenna.

A low beam / dipole can be "rope rotated" if the
clamp is not fully tightened.  Use a piece of 
1-1/4 inch PVC, slit lengthwise, to protect the
tower leg.

de  Tom  N4KG


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