Jim Thomson <mailto:jim.thom@telus.net>
Thursday, September 01, 2016 10:09 AM
Date: Wed, 31 Aug 2016 13:44:25 -0400
From: "Joe Giacobello, K2XX" <k2xx@swva.net>
To: sawyered@earthlink.net
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] 6 mtr quad
I am currently using a two element duobander on 30 and 40M on a 20 foot
boom. It's almost equivalent to a three element monoband Yagi but on a
far shorter boom. Cubex's 26 foot spreaders have held up well at this
windy QTH, although the combination of ice and wind can be destructive.
73, Joe
K2XX
## 104 ft is nuts. A full sized 40m yagi element is typ 62-74 ft.
Heck, a buddys
m2 80m yagi uses 101 ft eles.......on 80m, shortened of course.
The F12 340N uses 52-59 ft long eles, aprx 85% full size, and is only
10.3 sq ft,
135 lbs.
Well, hardly nuts. First, It does work and it's been up about ten years
with relatively few problems. Remember those spreaders taper down from
about a 1.5 inch diameter to around a quarter inch at the tips. A
three element Yagi has three +/- 65 foot elements and around a 40 foot
boom. That's not a trivial cross sectional area and a lot more weight.
I have turned the quad with either a Ham IV or a T2X. Heavy winds can
make turning difficult, but I suspect there's little difference with a
40M Yagi. Flexing spreaders during high winds have not caused me any
problems.
Your poor experiences with quads may have been in the early days when
the quality and strength of the fiberglass was far poorer than that
available today. I remember when I was first planning the 40M quad, I
spoke with W4QN, who was then the owner of Cubex. His spiders (hubs)
had arms only about (IIRC) 8" long, which I considered much too little
support for the butt end of the spreaders. He assured me that there
would be no problem, and he was right. I had considered trussing the
quad a la Gem quad, but it hasn't been necessary. Of course, you guys
up in the North Country have a different set of conditions to deal with,
which is the reason those Gem quads were so sturdily designed. (I never
realized that the "porcupine" spreader mount was a problem with snow/ice
accumulation.) OTOH, we do often get ice storms, wet snow and serious
winds here in the Blue Ridge.
I agree re the free standing tower, and I use LM-470s here. When I
originally built the 40M quad, I had used #12 Teflon coated wire (not
cheap) too and with the same expectation regarding minimal ice/snow
buildup. At that time my four element multibander was also up but with
bare wire. There was little or no difference between the two antennas
re icing.
73, Joe
K2XX
## One really needs a freestanding tower...or a freestanding crankup
when using quads.
Back in the 70s, I helped a local buddy install a 4 el cubex on top of
his 60 ft tall rohn 25 tower.
The only way it could be done was to remove the guys at the tower..as
the boom was raised
past each guy station...pita, never again. Then the quad was mounted 7
ft up the mast....and the
mast bent in a high wind one day. Another gong show.
## Then helped another ham with his 5 el cubex..on a 70 ft
freestanding tower. One day a 75 mph
wind comes along..and trashes his rotor..and also a spreader....at the
end of the boom on the REF..
another pita. Once all fixed, next up was a once in 20 year ice storm,
with .375 inch ice build up.
Wires broke on the 20m REF.....down it comes again. This time he used
teflon coated wire, thinking
ice would not stick to teflon. Wrong, sticks like glue, and more
problems.
## meanwhile, another local, with his gem quad has snow build up
issues. The snow was packed in
super tight, where the 8 x spreaders all converge into one point.
Looked like a 1 cubic yard block of snow.
Those spreaders they use, may well have won some BS engineering award
in VE4 lands years ago, but they
attract snow and ice really bad. All these guys kept a 15-20 ft long
pole at the top of the tower...so they
could climb the tower, and use the pole to smack snow + ice off
everything.
## after being in on several of these up-down-up-down-up-down quad /
delta loop install and repair
efforts, I vowed to never own one. Seeing broken wires and broken
spreaders tangled up with the guy
wires of a guyed tower will make you cringe. Then u get the other
issues, like high winds..and flexing spreaders,
at which point the wire loops all go slack.
## The 2 el, triband quad was a good ant in its day. One fella here in
town worked 300 countries with his gotham
quad, and had minimal issues with it.
Jim VE7RF
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