[TowerTalk] Cushcraft/MFJ Traps

[K9MA]

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

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