[TowerTalk] Cushcraft/MFJ Traps

[Glenn Pritchard]

Trapped yagis don't suck up gain, another myth easily dis-proven. I have
used trapped yagis and mono banders over the course of 30+ years and at one
time had the big Wilson 40M3 I believe it was called, 3 full sized 40 meter
elements on a 40' boom..
It is shown that maybe a trapped yagi has at worst a 0.6 dB loss over a
full sized yagi of the same band. It's no surprise that I like trapped
yagis because of space restrictions right now and having the ability to add
40 meters to one is skookum.

I would like to have mono banders only for 40 and 20 again, perhaps one day.

Glenn, VA7UO


On Thu, Sep 12, 2019 at 12:48 PM K9MA <k9ma at sdellington.us> wrote:

> I disagree, Jim. If trap losses were really significant, 1.5 kW would
> burn them up very quickly. Sure, a trapped beam is less effective than
> full sized monobanders, but can be made to work quite well. Witness the
> venerable TH7, which I used for 29 years very successfully. Not everyone
> has room even for a full-sized trapless tribander.
>
> I recently replace the TH7 with trapless tribander, not because the TH7
> performed poorly, but because I was concerned about bugs getting into
> the traps. It was almost 30 years old, and, as far as I could tell,
> performed exactly like it did when it was new.
>
> 73,
> Scott K9MA
>
>
>
>
> On 9/12/2019 14:42, Jim Brown wrote:
> > On 9/12/2019 11:22 AM, K9MA wrote:
> >> The moral of the story is don't even think about going to the trouble
> >> of putting up an MFJ/Cushcraft beam without taking apart all the
> >> traps and fixing the above problems.
> >
> > I have two very different takes on this. First, traps are an
> > inefficient way to build a multi-band antenna. That means they suck up
> > gain. Also, because the elements are shorter, their radiation
> > efficiency is reduced. The best multiband antennas don't use traps.
> >
> > Second, buying ANYTHING from MFJ is probably a bad idea. I was VERY
> > disappointed when G0KSC farmed out the NA production of his smaller
> > antennas to MFJ a few years ago. I've been very impressed with his
> > designs.
> >
> > 73, Jim K9YC
> > _______________________________________________
> >
> >
> >
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>
>
> --
> Scott  K9MA
>
> k9ma at sdellington.us
>
> _______________________________________________
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