I have a very small back garden so I am limited in the width of
antenna I can erect. I want to try and do better than a minibeam.
I am currently using a Cobwebb antenna which is a set of 5 nested
dipoles for HF bent into a square. For what it is it works quite
well, but I want to do better. I know it is not ideal, but I am
considering a 2 or 3 element trap yagi, but even with the loading
coils (yuck!) it is still too wide. So I am considering trying to
shorten the elements (particularly the reflector) by replacing the
outer tips (beyond the trap) with a shorter tip with capacity hat end loading.
I have modelled this in EZNEC for a simple 20m dipole (no traps) and
have got a feel for the cap hat sizes needed to shorten the tip by
varying amounts.
1) Has anyone tried this before? With what learning?
2) Is there likely to be a significant difference in effect putting
the cap hat outside a trap rather than on a straight element?
3) I am not sure I know how to model a 20/15/10 trap element. Does
anyone have an EZNEC model of a Mosley TA33jnr or Cushcraft A3S, or
advice how to build just a trapped element that I can play with?
4) Any other thoughts or advice would be appreciated.
73,
Dave, G3UEG
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