My previous posting provided an lengthy answer from W4LNB which might
help disspell myths about trap losses. He also provided his WWW address
and I found a lot of interesting data from a traped dipole simulations.
An example is given with 10/20m dual band traped dipole which shows max.
gain on 10m with trap resonant as low as 23 MHz. As the gain exceeds
the theoreical maximum for halfwave dipole of 2.15dBi, we are actually
seeing an extended dipole for higher frequency and shortened one on 20m!
It might be a good engineering RF practice to use the full lengths of
available antenna radiating wire but the impedance matching becomes more
complex and we eventually end up with my beloved Windom antenna fed at
1/3 with 1:4 balun without any traps! But a good RF choke is required
because of strong ground imbalance...
W4LNB wrote:
>To the best of my knowledge, coaxial traps have yielded the best trap Qs
>>(lowest losses), although they tend to be heavy.
I was told that coax traps exibit Q=60 because of poor L/C ratio.
We definitely know how to wind better and tighter HF coils and use good
high voltage capacitors instead of heavy lumped elements.
73 de Mario, S56A, N1YU.
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