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[TowerTalk] Rohn HDBX 40 - mast length

To: <towertalk@contesting.com>
Subject: [TowerTalk] Rohn HDBX 40 - mast length
From: <RShirbroun@newportlabs.com>
Date: Mon, 19 Aug 2013 13:17:44 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I have just erected a new HDBX 40 in place of my 30 year old HBX 48, 
sacrificing 8' of height to gain some strength and load capacity (and peace of 
mind!).  The stock rotator plate allows 2' of mast below the top plate and I 
will be using the heavy duty Yaesu thrust bearing (along with the Yaesu heavy 
duty 2800 rotator plus the absorber plate).   I have added steel angle braces 
to reinforce the rotator plate.

I'm looking at using a 15' chrome/steel 2" mast (in place of my previous 9' 
mast), so 13' of the mast would extend above the tower.  The mast would support 
a TX38 tribander just above the top plate, a 6 m beam half-way up, and a 40m 
rotatable dipole near the top, 12' above the top tower plate and the thrust 
bearing.  The mast, of course, is very heavy, weighing around 75lbs.  The 
tribander weighs 40lbs and with 5 ft2 surface area; the 6 m. beam weighs 10lbs 
with 1.5 ft2; the dipole weighs 10lbs and is 0.5 ft2.

Is this too much mast for this tower?   (BTW - I'm aware the boom length 
exceeds the 10' maximum for this tower, but the HBX 48 handled a similar 
tribander for 30 years, with occasional severe ice-loading, without any 
problems.)

Thanks and 73,
Randy, ND0C



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