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
Sent from my iPad
And YES it's cool!
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