48 Ft Booms

[Frank Donovan]

Hi Gary,

Nice to see a message without the N.... word!
My replies to your queries follow each of your questions below:

On Tue, 7 Jan 1997, Gary E. Jones, Ph.D. wrote:

> 1.  Don't you have problems with dissimilar metals?

I've never had a dissimilar metals problem with galvanized steel and
aluminum.  The situation may be much worse in coastal climates than here
in the Piedmont region.

> 2.  How far out do you support the booms when they are up?

Depends on the antenna design!  All of my boom trusses are made of 2100
pound Phillystran with Preformed Line Products terminations.  The 40M
trusses attach to the boom just a few inches from the elements attached to
each end of the boom.  The 20, 15 and 10 meter trusses attach a few inches
inward from the driven element and mid-way between the last two directors
at the opposite end of the boom.

>  3.  How long are the junctions that you turn out of chrome moly (2 feet?)

Yes, about two feet, but any length over 18 inches would be adequate..
Earlier I erroneously stated that the diameter was 2.74", in fact it was
turned down to 2.69" prior to hot dip galvanizing.  2.74" would not fit
after hot-dip galvanizing!

> 4.  I wouldn't think that 48' of 3" with a junction in the center would 
> hold itself together as its going up.. I guess that you have found that
> is not the case... that seems too long for that wall... must be tougher
> stuff than I think... 

No problem at all, Gary!  The 0.125" wall booms are very stiff and require
absolutely no TLC during installation.  

73!
Frank
W3LPL
donovanf@sgate.com



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