[TowerTalk] Misc. Feedline / Guying / Anchor Questions from a Newcomer
n4kg@juno.com
n4kg@juno.com
Sun, 30 Apr 2000 08:48:03 -0600
N4KG answers intersperced below.
On Sat, 29 Apr 2000 18:31:45 -0400 James Nipper <jnipper@southeast.net>
writes:
>
> After 25 years of using a Hy-Quad, I am going to put up a TH11DX, at
> 90 feet. My tower is a Rohn 25.
At 90 ft, you will find your antenna plays well at night,
is a good band opener and closer at sunrise and after
sunset, and during the summer when MUF's are lower.
During DAYLIGHT hours, you will find yourself waiting
in line behind the hordes of guys with LOWER antennas.
For full coverage of ALL of the angles which are supported
by the ionosphere, you need HIGH and LOW antennas.
I recommend another multiband antenna 35 to 40 ft, or
separate tribander and WARC bander. Fully rotatable
on a separate tower offers more flexibility. Side mounted
on the 90 footer is still better than NO low antenna. N4KG
I have several questions that I know many
> of you have expert experience on, and I would like to draw upon that
> experience. Some of these questions will seem quite elementary, but
> who> cares, huh??
>
> 1. Which is the best thrust bearing for me to use for this set-up?
With only one antenna on top, no need for a thrust bearing.
Since you have a 90 ft tower, I would recommend a GOOD
20 ft mast (10 ft in , 10 ft out) and a 2L40 on top. Put the
rotor shelf on the top rungs of the second section, cut one
horizontal brace on the bottom of the top section for access.
>
> 2. How high above the tower should my mast go? Stated differently,
> what is the ideal amount by which the beam should clear the
> tower?
The bottom antenna on the mast only needs to clear
the top by a few inches. Be sure the coax can clear
the tower without catching.
>
> 3. I am considering the Yaesu 800sdx rotor. Any real advantage of
> using the 1000sdx instead??
If you go with 2 antennas on top, a heavy rotor is
preferable.
>
> 4. I think that I have pretty well decided on using Phillystran. Do
> many of you fellows use it? Are there any drawbacks, except of
> course the expense?
Good idea. Good stuff. Use STEEL for the bottom
20 ft or so to prevent abrasion or susceptability to
fire or vandalism.
>
> 5. Which size Phillystran should I use ? 4000 lb, or 6100 lb?
> Should I use the same size at all levels?
4000 lb should be adequate if guyed at 30 / 60 / 90 ft.
>
> 6. I will only be able to guy at about 60% (instead of ideal 80%),
> so I plan to put my guy anchors in concrete for more strength.
> I will likely have about 2/3 cubic feet of concrete for each
> guy. Which Rohn guy anchor would you recommend ?
>
> 7. My coax run will be about 200 feet. I will need to direct bury
> the coax. What is the best, low-loss coax (not hardline). Does
> The Wireman (or anyone else) have any better offering than
> LMR400? Have many of you guys used the LMR 400 ?? Is it ok for
> direct bury?
>
> 8. What is the ideal length of mast?? Perhaps a total of 10 feet,
> with say seven feet down in the tower and about three feet above
> it?
That would be fine for only one antenna on top.
> 9. What is the best mast itself? With this relatively short mast
> (short distance above the tower, mainly) is aluminum alloy ok??
For a short mast, aluminum (or even galvanized water pipe),
is adequate.
> 10.I plan to use a remote antenna switch at the tower, so that I can
> switch from the beam to several planned slopers. Is it best to put
> that switch down near the ground, or up at the top?? I can see some
> pros/cons of both, but I want YOUR experience.
I like to have all feedlines available at the transmitters
for use with separate radios and improved reliability.
>
> -------------------------
>
> Well, I think that ten questions are enough for my first posting. I
> hope
> this isn't too much at one time, and I don't think any of these
> questions should be controversial. But then again, this is a ham
> list, hi hi.
>
> I do know that there is a wealth of experience on this list, and I
> will
> surely appreciate any comments that any of you may render, even if
> only> on one or two of my questions.
>
> 73 and the best of DX to all of you !! de Jim K4PYT
>
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