[TowerTalk] Some Unique Heavy Lifting....

[john at kk9a.com]

I would love to see photos of this full sized 80m beam. I wonder if the
element spacing could be designed to cover the whole band without switching
in inductors.  So, after you design this beast and install a commercial
tower for it, you still need a rotator. I do not think even Kurt's large
P.P. is up to that task.

John KK9A


To:	<towertalk at contesting.com>
Subject:	[TowerTalk] Some Unique Heavy Lifting....
From:	"Jim Thomson" <jim.thom at telus.net>
Date:	Tue, 7 Nov 2017 10:40:03 -0800

##  hats off to you Kurt !   I just spent the last couple of hours running 
numbers through YM.... for a full sized  80m REF.   What a bitch of a job.
I 
took my
40M  full sized  REF  design, that started at 2.25 inch OD x .240 wall...and

tapered down to .375 tips.... and simply started adding bigger and bigger OD

sections inboard.  
I was up to 4.5 inch OD x .316 wall  to get anywhere decent  for 
windload...with no ice load.  Then started playing with  single and multiple

overhead truss lines, trussing each half of the REF, in
1-2-3 locations.   Even then, the  overhead truss lines dont do anything for

horz deflection, so started adding more truss lines in the horz plane, to 
minimize horz deflection. 
It all sorta works in the end, but I wonder if at that point,  Im designing
a 
80M REF.... or  a  biplane  or triplane, with truss lines galore !  It was
more 
of a fun exercise to get a feel for what is involved.
The weight of the 80M REF alone ends up beyond crazy, like 360 lbs, not 
including any hardware or truss lines.  
Aluminum tower sections, for the in board ends,  just might be  a better
bet.   
 But I have zero experience  with Aluminum tower sections used as eles.   

## IMO, this is one place where loaded 80M elements  would be a godsend.   
Something more reasonable in length, like say  90-94 ft max, with 28-32 ft
long 
T bars..aka capacity hats, and 
a seco systems tornado drive at the feedpoint,   would greatly reduce the 
weight... vs the 146 foot long REF on the full sized 80m behemoth.   With a 
tornado drive at the center of each element,
then the entire array  could be tuned for max FB  and flat swr across the 
entire band from 3500-4000.   Any helical hairpin would be a trick, not an 
issue if a 3 el used, and the DE could be gotten
to at the top of any tower.  On a 2el, perhaps either a much smaller 
compressible coil assy could be used, or vac relays employed to change taps
on 
the hairpin.  

##  The weight piles up... fast on these large arrays.   Then you have to
get 
it up there, keep it up there..and also rotate it. 

Again, kudos to anybody  who tackles these massive projects. 

Jim   VE7RF