[TowerTalk] BIG clamp on issue

Jim Thomson jim.thom at telus.net
Wed Jan 17 15:41:34 EST 2018

Im in the middle of some CM  experiments..using a single large clamp on, in addition 
to some 2.4 inch od cores.  For interest,  I connected my  B+K  875-B  digital lcr meter 
to the shield at each end.    These large clamp ons  are a six sided affair, on the outside. 
I measured  120 uh with just the torroids.  That increases to 137 uh with the addition of
one large clamp on.   However, with one side of the  big clamp  on, firmly against the inside
of a thermoplastic box, and squeezing really hard on the opposite side, the inductance increased
to as much as 157-158 uh !   Let  go, and it drops back down to the 137 uh region.   In both cases
the hinged section was shut solidly.   Ok, so what gives here ?   My plan was to use  2-3 x ty raps
and tighten the clamp on really good. 

##  I think the issue is the mating surface gaps on the hinged portions.    There is a pair of mating surfaces
at the 9 oclock position..... and another pair of mating surfaces at the  3 oclock position.   In this application, there
is only 3 turns of  RG-393  passing inside the big clamp on, so there is room for the 3 turns  with no fitment issues. 
The ID of these large clamps ons is  1 inch. 

##  Is this normal for these large clamp ons ?   I have never used them b4.  I was thinking of  88 tape to keep em
firmly closed,  but  2-3  wide ty-raps can be cinched up a lot tighter than any tape job.   Or do I use one wrap of tape
1st, then a ty-rap dead centered on the tape job. 

Jim   VE7RF.    

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