Deja vu all over again? Didn't like our responses then?
Gary posted 4/18:
Hello from N5PHT,
I am N5PHT, Gary, writing from Savoy, Texas. I have a tower and new
antennas project in the works and it is exciting to me but I have some
questions. I am putting up a 45G at 80 feet. The antennas on top of the
beam: Optibeam 17-4 and the WARC-7 above the big Optibeam.
My first question is about separation? I have read that you can put them
closer if you put one of them 90 deg out of the other. I have a
22 foot mast and will be using the M2 2800DC with two thrust bearings so
that will leave about (?) 18 feet above the top of the tower. What
separation would be good to have both antennas aimed the same direction? I
would think 10 to 12 feet would be fine? If 10 feet is ok that would allow
me to mount the rotator a bit further into the tower?
Secondly, does anyone have experience with putting together the OB17-4 (or
the WARC7 for that matter)? The OB17-4 weighs in at a little over 200 lbs
and has a 39 foot boom. The WARC-7 is much smaller. Any tips on either of
these antennas appreciated?
Third, what about antenna height? I am thinking that 80 feet is much better
for the 3 elements on 40 meters but is that too high for 20 or
15 meters? I realize many hams put up antennas very high, well over 100
feet so I am thinking 80 feet is no problem for any band 10 - 40 meters?
Lastly, any speculation on the improvement this will be over my Cushcraft
A4S at 45 feet for 10, 15 and 20 meters? I am looking forward to have some
gain in other bands, especially 40 meters!
73 de N5PHT, Gary
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Gary Stone
Sent: Wednesday, April 27, 2005 9:39 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Tower height questions
Hi to all,
I am currently planning on an 80 foot tower - Rohn 45G. I am interested to
know if there is data or personal views about two things:
1- Antenna height. My plan is to put up an Optibeam
OB17-4 at about 82 feet (77' tower plus a few feet of the mast and the
OB17-4 would sit right above the tower - so a height of 82 feet).
QUESTION: How would the performance differ if I dropped one section of
tower? That would leave 67 feet of tower and the antenna would therefore be
at
about 72 feet? This antenna has 3 elements on 40
meters and that would be my most concern on the 10 foot drop? I don't think
10,15 or 20 would suffer too much from 82 to 72 feet but I am not sure about
40 meters?
2- Strength. The 45G will be guyed in two places.
What would be the suggested guying placements for the
77 foot and for the 67 foot? I would think for the 77 foot the first guy
would be at 35 feet and the next (and last) at about 65 or 70 feet? But
would the 67 feet still be guyed about the same: 35 feet and maybe then
again at 63 feet or so. IF I go with this 10 foot less what would be the
strength gain since I will still be using 2 sets of guys.
Overall my goal is to have a better performer than my current A4S at 45
feet. I also don't want to sacrifice 10 feet of tower if it will make a
marked difference.
The main consideration is that I can easily get a crane into the right place
but the tip of the crane goes to 87 feet only so if I drop on section that
would be very manageable.
Thanks in advance for any ideas?
73 de N5PHT, Gary
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and ask for Sherman, W2FLA.
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