I've read somewhere that traps should be tuned below the band of
interest.
Then adjust the loading wire to compensate. That reduces the extremely
high
RF voltage across the trap.
Charlie, N0TT
On Sun, 24 Oct 2021 01:32:13 +0000 WW3S <ww3s@zoominternet.net> writes:
> 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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> >TowerTalk@contesting.com
> >http://lists.contesting.com/mailman/listinfo/towertalk
>
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>
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