Date: Wed, 24 Nov 2010 13:30:39 -0600
From: Chuck <Chuck@dxham.net>
Subject: Re: [TowerTalk] Cushcraft Parts From MFJ
On 11/24/2010 1:00 PM, Larry & Karen wrote:
I immediately thought of putting up a HyGain 6M antenna, so
I called Burghardt's and they sent me one right down.
The antenna LOOKED just like the ones made in Lincoln so I proceeded
with the assembly and installation. Many small parts and lots of
measurements and adjustments later, I had the beam mounted atop my 100ft
tower. The antenna performed as I expected a 4el beam to perform. SWR
was reasonable.....for awhile.
Here on the plains of Western Iowa, we get frequent high winds and many
storms. One day, I decided to get on 6 meters and make some contacts and
my SWR was way out of whack. I went out back to the tower and saw that
half of one of the elements was totally MISSING! I found it out in the
corn field a little ways from my tower.
#### Did the ele to boom clamp break, or did the ele just snap off,
right at the boom to ele clamp ?? What was the wind-speed ?
Unfortunately, after dropping the antenna down and replacing the element
with one I had on-hand, we reinstalled it only to have a different
element break off a couple weeks later! All in all, I lost 4 half
elements in less than 6 months. We yanked it down, boxed it up and off
it went back to Burghardt's! What a wonderful company! Jim credited me
the full price towards a new 5 element M2 6M5X beam, which I installed
in the spring. What a difference! The M2 antenna has been up for 8 years
now and performs flawlessly!
## This is bloody awful ! But that was >8 years ago too.
All you have to do is insert all the entire ele tubing schedule,
OD's, ID's, various wall thickness's, AND yield strengths, alloy's, temper,
into YS 2.15 OR the DX eng software, or ON4UN's software, and it will tell
you
exactly how much wind it will take, [with and without XXX ice]..and also
tell you exactly WHERE it will break.
## My guess is, instead of using 6061-T6 or 6063-T832, they have gone
to a cheap alloy, like 3003, which comes in various grades of hardness, listed
as H-0 to H-14. H-0 is only 6 ksi yield, and the strongest is no match
for
6061-T6 or 6063-T832. 3003 H-0-3 is used for refrig tubing..and comes
in 50'
rolls ! Another famous US ant maker tried using 3003 [ H unknown], for
ele
tips, and all the tips failed !
## a local ham went dumpster diving at the local airport, where an aircraft
rebuild
business is located, and obtained enough tubing to build 2 x 15m yagi's.
In the
1st wind storm, ALL the ele's bent badly... right at the boom ! Turns out
he had
pilfered 2024-T0 tubing.....which has zip for yield strength. Normally,
2024-T0
is 1st bent into various U shapes, for small aircraft tail sections, then
drilled, bent,
etc, etc,... THEN sent in for heat treating...where the max you can heat treat
2024
is T-3 [ aprx 45 ksi yield]. 2024-T0 has very little yield strength,
which is not readily
apparent when building yagi ele's.
Chuck K?TVD
> I have to agree with Ted on the quality of MFJ. I have had both the old and
> the new Hy Gain for example and my experience with the new has never been
> good. They have cheapened the HY Gain line to the point where it is
> basically junk. For example, I can understand and element breaking off in
> high winds,
but the last two feet of the element out at the end? Twice? Take a six foot
section of the boom of
> any MFJ/HY Gain tribander and hold it in one hand and in the other hold the
> exact same piece of an actual HY Gain boom from the past and tell me which
> one you want to put in the air. No contest.
## OK, is the wall thickness the same ? Or did they reduce it ? I assume
the OD is still
the same ? My old 6-el F-12 yagi only weighs 45 lbs..and boom consist of
6 x 6' sections,[all 2" OD]
nose to tail, with outer sleeve splices. They used .125" then .058",
then .049" for the boom
[repeat for other 1/2]. YS-2.15 says the boom is good for 122 mph.
F-12 uses 6061-T6 for
booms and eles. The new F-12 stuff uses bigger diam and thicker wall
booms. They have also done
away with all the .049" wall tubing and ele swedging, and have gone to all
.058" wall stuff.... including the
3/8" OD tips. [ old tips were all .035" wall].
## IMO... unless Hy-gain/ MFJ can state the exact alloy and temper of
both their booms and els [and those
flaky clamshell boom to ele brackets]... I would not touch their ant products.
It appears they have either used
a cheaper alloy /and /or the old alloy, but a softer temper... or both. IF
we knew what alloy/temper/yield strength
they used,it would take all of 2 x minutes for the software to spit out
exactly what windspeed it will break at.
6M els, made from 3/8" and 1/2" tubing [6061-T6 or 6063-T832] are good
for > 100 +++ mph easily.
Lemme guess, the pricesare the same, or slightly more than the original
hi-gain's ? This is probably a
case of [A] use cheap AL for the boom and eles... and [B] keep the price
the same, and [C] therefore enhance profits.
Joe ham will not have a clue what alloy /temper his shiny new hi-gain yagi
is built from. New/old Hams
will then assume that broken els in 65-80 mph winds is ...'normal'. It's
not folks.
They are selling you a bill of goods, plane and simple. US products are
very expensive outside the usa, esp ants,
and that's a lot of money down the drain. Shipping costs to sent the old junk
back to the factory, and back again, is
cost prohibitive...and a waste of time. IE: no point in replacing a damaged
mfj / hi-gain yagi, with a 2nd, identical
one.
later.... Jim VE7RF
> 73, Larry K0IS
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