Such a traps are described in Chapter 9 of ON4UN's "Low Band DXing" book.
together with proposed LC tuning units.
73 Mirko S57AD
V V ned., 24. okt. 2021 ob 06:18 je oseba Jeff Blaine <
KeepWalking188@ac0c.com> napisala:
> Back in the attic antenna days, I used a trap 160/80 at the house. Was
> running CW & RTTY then and kept frying coax type traps. As they heated
> up the SWR would move around and you could see it on key down. The
> failures of those coax types were impressive! Lucky I did not burn the
> house down, when I think of it in retrospect.
>
> Eventually went to a 1/4" copper tubing + Russian fixed vac cap
> construction type - and that was the end of those trap failures. The
> trap was a monster, but it was low loss, high Q and indestructible.
>
> 73/jeff/ac0c
> alpha-charlie-zero-charlie
> www.ac0c.com
>
>
> On 10/23/21 8:32 PM, WW3S wrote:
> > 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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> >
> > _______________________________________________
> >
> >
> >
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--
Mirko S57AD
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