[TowerTalk] 2 vs 3 ele 40m yagi - opinions?

[Jim McDonald]

My experience with the F-12 EF-340D, the predecessor to the MAG-340, seems
to have been better.  The original boom/mast bracket broke, much like the
picture in QST (February?).  I should have checked before it broke apart,
but the boom guys held it.  Had lots of wind in Albuquerque but that bracket
was the only failure.  The "D" model is rated at 100 mph rather than the
standard 80 mph, and the "H" model is rated at 120 mph.  F-12 even has an
"HH" model in the catalog for 140 mph.  The higher wind ratings appear to be
available for most antennas according to the catalog.

I just replaced the bracket with the new Mangum one, and it's about three
times the size and significantly thicker.  I asked for whatever it takes to
make it into a MAG340 and got new linear loading wire (seemed to be the
same), the beefy bracket, and new fiberglass spreaders (with crimped
aluminum center tubes) to support the linear loading wires.  Will put in up
near Phoenix near some mountains so we have quite a bit of wind, and I'm
comfortable with it.

Jim N7US


----- Original Message -----
From: "Robert Cummings" <robert@gi0kow.freeserve.co.uk>
To: "Dan Levin" <djl@andlev.com>
Cc: "tower talk" <towertalk@contesting.com>
Sent: Tuesday, February 06, 2001 3:29 PM
Subject: Re: [TowerTalk] 2 vs 3 ele 40m yagi - opinions?


>
>2) I have to choose whether to use full size 40 meter elements, or to load
>them somehow (probably capacity hats at the ends of the elements.  4 2'
>spokes shortens the elements to about 56' - 8' of hat spokes saves 5.5' of
>tip length (per side).  Maybe F12 style linear loading line the new N
>elements.).
Not sure what the difference is between the F12 N elements and what they
used on the Mag 340 but if it is similar to what was used on the Mag 340
be sure to design yours to a much stronger standard than what F12 use.

My Mag 340 has failed in this area (and in most other areas) and is
pretty much ready for the scrap heap.

Make sure you over-engineer the components
Good luck with the project.
73
--
Robert Cummings GI0KOW

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