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[TowerTalk] Butterfly Beams

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Subject: [TowerTalk] Butterfly Beams
From: (L. B. Cebik)
Date: Fri, 6 Feb 1998 06:21:21 -0500 (EST)
The other side of the coin on the HF5B.  I have used one for over 10
years.  In that time, I have changed local QTHs.  I disassembled the
elements from the boom and (thanks to a considerate mover) reassembled the
elements to the boom at the new QTH.  I have also periodically lowered the
small tower I use (antenna presently at 35'--but atop a rather large hill)
for regular preventive maintenance checks.

Tuning up the HF5B took a whole afternoon originally.  Thereafter, the
beam has remained in tune without change of any dimension of the matching
networks.  Only an occasional precautionary screw-nut tightening has been
needed during maintenance checks.

On 10, the antenna is a solid 2-element Yagi, with proper F-B for that
band (about 2 S-units).  On 15, performance is similar.  (The natural
resonance of the fans is about 25 MHz.)  On 12, the antenna performs
backwards, with less F-B.  On 17, it is essentiall a dipole, shortened.
On 20, the antenna displays some F-B, but no especialy gain.  On all
bands, F-Side is quite good--as it would be for a rotatable multiband
dipole.  These figures are close to what the spec sheet shows.

The key to making a durable structure is patience in assembly and tune-up,
and doing things in the order specified in the manual.  I did my initial
tuning with the beam pointing straight up (or nearly so) with the
reflector about 10' off the ground.  (Flip for 12 meters.)  Use great care
in assembling the matching elements, including the use of the junction
compound where specified.  Use care also not to overtighten element to
boom and boom to mast junctions--and be certain of alignment before
tightening, since the tubing will deform slightly into a permanent shape.

Certainly, there are multiband beams with much higher performance
specifications in terms of gain and F-B.  However, for my type of casual
and net operation, where excessive F-B is sometimes a hindrance, the HF5B
as proven itself very satisfactory.  For other types of operation, it
would not be adequate.

For a beam with such a small footprint and light weight, the HF5B acquits
itself well.  If I wish sometimes for better 20-meter performance, I then
compare element lengths and ask myself if I am ready to maintain 35'
elements vs. 13' elements.  The antenna has survived multiple occasions of
winds in excess of 50 mph at my two locations of use--it slips the wind
very well.

If you need the gain and/or F-B and have the space and maintenance
abilities, then by all means select a larger beam.  If you need more than
a little F-B on 20, then also select a beam designed for 20.  If you need
high performance on 12 and 17, then buy or build a beam for those bands.
However, the HF5B has a niche for those willing to use care and patience
in assembly and tuning (including a non-frustrated willingness to reset
the components for a given band back to their starting points and to do it
again) and who need only casual operating abilities in a confined space.
I would not recommend heights below 35' or running the spread fan ends too
close to a roof top or other object.

I have no connection with the company and paid full price (at the time)
for my HF5B.  Also, I have never expected more of it than the design would
allow.  Within those parameters, it has met all electrical specifications
and has been mechanically very reliable.



L. B. Cebik, W4RNL         /\  /\     *   /  /    /    (Off)(423) 974-7215
1434 High Mesa Drive      /  \/  \/\     ----/\---     (Hm) (423) 938-6335
Knoxville, Tennessee     /\   \   \ \   /  / || /      (FAX)(423) 974-3509
37938-4443     USA      /  \   \   \ \       ||    

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