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August 20th 03, 07:16 PM

(VE8AE Andrew) wrote in message . com...
I have an old Shakespear 32 ft antenna. Fed at side near bottom and a
large bottom plate. Want to know if I mount it up at the top of a mast
how long should I make radial wires for? Do I just calculate for
lowest freq and make them 1/8 wavelength? I am going to run it through
my tuner to get as many bands out of it as I can. Only about 40ft of
coax so it is not too long.
Or should I try and design my own trap vertical of some sort??
Thanks.
Andrew VE8AE

I assume it's an unloaded fiberglass whip....Perfect for a 40m
antenna. If elevated, use 1/4 wave radials "appx 32-33 ft". Trim for
best match. You could feed it as a 5/8 on 17m with a small series
loading coil at the base. It should work ok on 15m, if you use the
tuner. The other bands, the feedline and tuner losses will vary. Just
try it and see. For any certain band used, you would prefer at least
one or more 1/4 wave radial. But 3/4 wave radials can work also. So
40m radials can double for 17 and 15 with decent results. If you try
to use with a tuner on bands where the match is lousy, I would prefer
a thicker low loss coax. So I would use rg-8/213, etc instead of
rg-58. Matched, the differece is very small, but I think it can
noticeably reduce losses a bit when you have a big mismatch. The
higher the freq, the more you would notice the difference. On the low
bands, it would hardly matter. You could feed it as a 1/2 wave on 20m
with very good results, IE: gamma loop feed, but that matching scheme
is going to be quite different than a 40/17 antenna. If you do this,
consider it a single band antenna for the most part. You would need to
pick one or the other. Hard to do all at the same time. Maybe use a
autotuner...But autotuners seem to be sort of lossy in such cases.
Also, if you use a loading coil, say for 17m use, it's best not to
ground the base. Just run it in series. You don't really want to dc
ground an antenna you are trying to run on all bands with a tuner, or
even dual band like the 40/17 combo. If you ground the coil, it will
ruin it on 40m. If you don't ground the coil, it just drops the
resonant freq on 40m a bit. I used a 24 volt relay to switch on one I
ran. MK

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