my recent 80M trap experience.....my previous 160m ant was an inverted L
suspended off a hazer on my Rohn 25 tower.....when higher winds or
storms I cranked the hazer down, so was out of business on
160M......been looking for an alternative, and one of my other antennas
is a Hygain Hytower.....most of what I heard about the 160M kit for the
Hytower wasnt good......I just so happened to have a W2AU 80M trap with
the ability to mount via tubing......so.....bright idea, I would replace
the stinger on my Hytower with different size tubing, allowing me to
mount the trap on top of the hytower, and attach a loading wire to
it.....I had most of the tubing I needed, ordered what few pieces I
needed....I built the new stinger to the length of the old one (probably
my first mistake), attached the trap, and about 47 ft of wire (per the
instructions from Unadilla for a wire antenna)......tilted the tower
back up, swr was a little higher than before on 80M, but was less than
1.5:1 at 1820 so I left it.......worked a few stations on 160, worked a
few on 80, everything seemed good......until........until I tried to
work S9OK on 160M.....with the amp.....at about 1400 watts.....calling
for about an hour and them something went south in a hurry.....swr all
over the place on 160 and 80.....I havent had the chance to tilt it back
over but I suspect the trap overheated.......another bright idea that
wasnt so bright after all.....
------ Original Message ------
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Sent: 10/23/2021 2:54:20 PM
Subject: Re: [TowerTalk] 80 Meter trap design needed
On 10/23/2021 4:56 AM, Mark - N5OT wrote:
I hope to make a trap vertical that works on 80 and 160.
First question is, why a trap? If it's not height, consider a fan.
Second, there's a design for 2-band 2nd harmonic dipoles where there's a
loading coil (NOT a trap) near what would be the quarter-wave point of the
lower frequency band, with a relatively short wire beyond it. That design has
relatively narrow SWR bandwidth on the lower frequency band, but bandwidth
comparable to dipole on the higher band.
This design works quite well, and there have been several successful commercial
implementations of it. Hypower Antenna Company (tiny ad in QST) sells them, and
may sell the loading coils separately. I measured their coils for the 160/80
and 80/40 designs many years ago, and can probably find the data. But it's a
fairly easy design to do in NEC, and I recently did one for a 40/20 dipole made
from Al tubing for use on CQP county expeditions.
73, Jim K9YC
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