[TowerTalk] Booms

[jimlux]

On 3/10/17 7:12 PM, Ed Karl wrote:
> Hey Troops-
>
> I've been around for a while, always wondered about this. Looking at the
> discussion
> of square vs round booms. How come the elements are on top of the round
> book?
> Seems like less inclination to rotate out of alignment if they were
> already on the bottom ...
>

Tradition?
Elements are on top with round booms too, probably because of assembly 
processes
If you're assembling it on sawhorses, it's easier to have the boom 
sitting there, and then bring the elements over and mount them one by 
one, on top of the boom. If they're on the bottom you have to thread 
them around the sawhorse legs, etc.

And then once it's assembled, who wants to try and flip it over 
(although it's not that hard, it is unwieldy.

I can't think of any *electrical* reason why you'd care.   On some 
LPDAs, the elements alternate top and bottom (both across and along the 
boom) if the boom is the transmission line.


(and we'll leave aside any theories about the fact that the north facing 
owl will tend to sit on the element rather than the boom, because it's 
higher, and if you put the elements on the bottom, you'll have a 90 
degree pointing error...)

On VHF/UHF arrays with CP antennas, a common error is to not have all 
the antennas oriented the same (there's this tendency to make it mirror 
symmetric, because it "looks" more balanced). I may overstate, I've seen 
this error once, but I've only seen an array being assembled a few 
times.  Generally by the time most people look at it, it's been fixed.