[TowerTalk] Cushcraft/MFJ Traps

[K9MA]

Since MFJ also owns Hy-Gain, it wouldn't surprise me if they were using 
a common trap design. If so, I'd suspect the Hy-Gain traps would have 
the same issues. Has anyone seen the insides of one?

I can't tell what kind of material they're using for the coil form. Two 
of the MFJ traps are currently on my A3, but I think I'll put the 
originals back.



73,
Scott K9MA

On 9/12/2019 16:54, Glenn Pritchard wrote:
> Scott,
> That looks a lot like the Hy-Gain trap design they used years ago that 
> MFJ is now using. They had that plastic trap form that cracked easily 
> under pressure. I had an old 18AVT that used those, meh.
> Why on earth they went cheap is beyond anyones guess.
>
> Glenn, VA7UO
>
> On Thu, Sep 12, 2019 at 2:44 PM K9MA <k9ma at sdellington.us 
> <mailto:k9ma at sdellington.us>> wrote:
>
>     Here are links to photos of the A3 TC 15m trap, the original
>     Cushcraft
>     version circa 1992 and the recent MFJ one:
>
>     sdellington.us/hr/TC_CC1.jpg <http://sdellington.us/hr/TC_CC1.jpg>
>
>     sdellington.us/hr/TC_MFJ1.jpg <http://sdellington.us/hr/TC_MFJ1.jpg>
>
>     Note the two pop rivets in the CC trap, missing from the MFJ one.
>     There
>     are two more rivets on the other side. The extra screw in the CC
>     trap is
>     one I added.  Note also that the wire on one end of the MFJ coil is
>     wrapped the wrong way. Originally, both terminations looked much
>     worse.
>     Later, I wrapped both the right way, and added SS flat washers. I
>     also
>     fixed that almost shorted turn.
>
>     The MFJ trap has 4 fewer turns than the CC trap, though the
>     resonance is
>     about the same. It looks like the MFJ coil form is slightly larger.
>
>     I don't like to bash MFJ, as I think they provide a useful service to
>     the ham radio community, but I do wish they paid more attention to
>     QC,
>     especially for antennas, installation of which involves a lot of work
>     and expense.
>
>     73,
>
>     Scott K9MA
>
>
>     On 9/12/2019 13:22, K9MA wrote:
>     > I recently ordered some replacement traps for my old A3S. One was
>     > defective, so I took it apart. I was appalled at the poor quality.
>     > While the original traps had several pop rivets, in addition to the
>     > coil screws, connecting the tubing to the plastic insulator, the
>     MFJ
>     > version had only the two screws in the very end of the tubing. The
>     > coil wires were sometimes wrapped the wrong way around the
>     screws, and
>     > some of the screws weren't even tight. Where the original coil was
>     > coated with some kind of thick lacquer, the MFJ ones were bare.
>     >
>     > 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.
>     >
>     > 73,
>     >
>     > Scott K9MA
>     >
>
>     -- 
>     Scott  K9MA
>
>     k9ma at sdellington.us <mailto:k9ma at sdellington.us>
>
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> -- 
> /Never believe and Atom, they make up everything../


-- 
Scott  K9MA

k9ma at sdellington.us