Yes, I know traps are a compromise and some people don't like them, but
my feeling is that it is often the design and construction that are the
main problems.
I plan to build one for 15m (for a 15m/20m elevated vertical) using a
heavy duty doorknob capacitor and small diameter copper tube for the
inductor, which should optimise the construction issue.
Question 1) What should the design frequency be? I vaguely remember
reading somewhere that the design freq should **NOT** be the middle of
the higher freq band (eg 21.225 in this case) but on some other freq
somewhere between 21MHz and 14MHz. I have done several Google searches
and cannot find any references, in particular I would like to know the
reasoning behind doing this, and how using such a mid-freq affects the
length of the two parts of the antenna?
Question 2) Are there likely to be any issues measuring the resonant
freq of a trap using a RigExpert AA-54 analyser, or is there a better
way? Again I vaguely remember reading that a dip oscillator is the
best way, but I don't have access to one.
73,
Dave, G3UEG / K1MDX
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