[TowerTalk] Bushcraft Traps
K9MA
k9ma at sdellington.us
Wed Nov 13 15:17:30 EST 2019
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
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
--
Scott K9MA
k9ma at sdellington.us
More information about the TowerTalk
mailing list