[TowerTalk] TowerTalk Digest, Vol 201, Issue 54

[Marv Shelton]

I have a 1980’s vintage Cushcraft A4 and just replaced it with a 3 element SteppIR.  I had the 40m add-on as well and never had a problem with it. 15 meters was it’s best band.  Only once did I take apart the traps and service them. Cleaning out bugs, and using scotch-brite and conductive grease with new SS hardware to make sure all the connections were solid. 
I once saw where someone had designed a special jig to measure and test the traps because the labels had worn off.  I do know that MFJ did a redesign and their traps are not made the same way nor at the same frequency as the original Cushcraft. I would compare the assy instructions for the two as I would the guess the element lenghts are different as a result and mixing MFJ’s traps with original Cushcrafts would require some modelling/tinkering to get things working right.
It sound like in your rebuild that you may have mixed traps in the wrong locations, as 20 meters represents the lowest freq band, it uses the total electrical length of the elements and the order of traps on the element isn’t important. For 10 meters, the electrical length is the shortest, so as long as there is some kind of trap in the 10 meter position, you a likely to get resonance somewhere in the wide 10 meter band.
You can’t go by the physical length of the traps to determine which one is for which band. You need to build a jig to test them. Due to their physical design inductive coupling to measure them is tricky.

Marv K7IU

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And YES it's cool!

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