[TowerTalk] Bushcraft Traps

[K9MA]

Unfortunately, I've recently had a lot of experience with Cushcraft traps.

To get them apart, remove the end caps, place the inboard end on a vice 
with the jaws just catching the case (not the insulator), and use a 
block of wood and a hammer to drive the innards out. Carefully.

The difference in TB and TC is a small difference in resonant frequency. 
TB may have one fewer turn, or it may just be tuned higher with the case 
position and/or number of outboard insulators. I don't know about TD and 
TE, but the higher resonant frequency probably goes in a director.

The best way to identify the traps and determine if they're working is 
to measure the resonant frequencies. (I can find the data, if you want 
it.) I found it almost impossible to couple a dip meter to the trap. 
However, I was able to measure the resonance by placing a probe on 
either side of the outboard end, extending just beyond the end of the 
case, so they were loosely capacitvely coupled to the center tube. One 
probe came from a signal generator (just a clip lead coax), the other 
was a 10X scope probe. At resonance, I could see a sharp peak on the scope.

The original Cushcraft traps are built much better than the new MFJ 
ones. If you're using the MFJ ones, I can suggest some modifications.

Hope that helps. Contact me offline for more info.

73,
Scott K9MA

On 11/13/2019 13:02, Tom Wylie wrote:
> Anybody got good advice re the opening up of traps for an A4S without
> destroying them.  What physical difference is there between TB and TC.
>   And TD and TE?   The markings are worn off the traps
>
> Tom
> GM4FDM
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-- 
Scott  K9MA

k9ma at sdellington.us