[TowerTalk] 25G vs 45G

[n4kg@juno.com]

Two factors come to light when you carefully compare the
R25 and R45 drawings and specifications.

First, as has been pointed out before, R45 ASSUMES an 8 sq ft
side mount fixture already applied (see note 4).  This number can
be added to the R45 antenna load if no sidemount fixture is used.

Second, the TOP guy wires are NOT placed at the same positions
relative to the top of the tower.  One of my catalogs shows R45
guyed 9 ft below the top for all heights while showing the TOP guy
wires placed 5 ft below the top of the tower for R25.  

Another catalog shows the TOP guy wires placed either 5 or 15
ft below the top of the R45 tower, depending on total tower height, 
versus placing the TOP guy wires only 2 ft below the top of the
R25 towers.

Remember, GUYING arrangements shown in the Rohn catalogs
are NOT the only options.  They represent specific applications,
usually commercial, which are typically NOT optimized for 
Amateur applications.

Regarding your placement of your KT34XA at 80 ft, I would want
to either stack two tribanders or place the single tribander at
60 ft.  My 80 ft high tribander (TH6) is my WORST daytime
antenna on 10 and 15M.  Other antennas (TH7 at 40 ft and
monobanders at 40 and 60 ft) are almost always better when
the sun is up.

Second, I would recommend a good strong mast (1/4 inch wall,
>90,000 psi yield strength) and a "2L shortie 40" placed 10 to
12 ft above the tribander.

de  Tom  N4KG


On Tue, 11 Jul 2000 18:52:16 EDT TheMardster@cs.com writes:
> 
> I am getting ready to put up my first "real" tower. I am trying to 
> decide 
> between Rohn 25G and 45G. On the Rohn website, the windload specs 
> for 25 and 
> 45 are virtually the same at 80 feet. Is this true? How can this be 
> correct?
> 
> I will be putting up a KT-34XA on top with various VHF antennas. 
> There will 
> also be a 40m-10m rotatable dipole at 60 feet or so. Later I would 
> like to go 
> with a Force-12 C31 on top and replace the dipole with the KLM. I 
> think I 
> should be able to get by with 25G. (70MPH zone)
> 
> Any help will be appreciated.
> 
> Thanks,
> 
> Marty, N9SE
> 
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