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@sdellington.us
<mailto:k9ma@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@sdellington.us <mailto:k9ma@sdellington.us>
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--
Scott K9MA
k9ma@sdellington.us
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