Bottom posted...

"Dick, AA5VU" wrote in message
...
In article 2%HQf.12296$wH5.7544@trnddc02,
"Dale Parfitt" wrote:

Absolutely zero reason to place that wire in series with the dipole- in
fact
it will not yield the same results if you do so- you will end up having
to
redo the length. It will also mechanically weaken the antenna and also
change 80M resonance. There is no current in that short stub-i.e. no
effect
on radiation. Let it dangle.
Dale W4OP

Thanks..... going to let it dangle. Not hurting anything and it has a
good attachment.

Hi Dick,

Dale has got it EXACTLY right here! Variable-length stubs from the
inboard screws on the "resonactors" is how Bill (W9INN) INTENDED
his antennas to be tuned! He called this--logically enough--"stub tuning."

The obvious advantages of stub tuning a
1. It's much easier than changing the length of the primary antenna wire,
and
2. The two (or more) bands can be adjusted INDEPENDENTLY of each
other; i.e., changing the length of the 40m stubs does not affect 80m
tuning; and changing the length of the 80m stubs does not affect 40m
tuning.

This is absolutely the right way to build dipoles in which precise tuning of
resonance is desired.

Now that you've got your 40m resonance set to mid-band, you're pretty
much done on 40m; you can get the full band under 2:1.

But 80m is another story. Because of the "resonactor" loading (which
conveniently reduces overall length), your 2:1 BW is probably 90 to 140 kHz.
By changing the 80m stubs, you can put this wherever you want in the 80m
band; but it's still pretty narrow.

I made a small mod on my W9INN 80/40/17 dipole by putting Rat Shack
banana sockets on the ends of the primary 80m stubs. This enables me to
swap stubs (each with its own banana plug), to move the 80m resonance
around in the band. Because my antenna is in an inverted vee configuration
with fairly low ends, it's easy for me to change the stub(s).

My normal tuning point is 3950 kHz, where I get 1:1 SWR. To move to
3850 kHz, I plug in ONE stub of appropriate length. (Absolute mechanical
symmetry isn't necessary; in fact, asymmetry in the preferred direction can
actually lower SWR.) It takes me 90 seconds to go from my second-floor
shack out to the antenna, make the change, and come back again.

Naturally, the WX is sometimes such that I don't want to go outside and
play with stubs. That's one reason I just replaced my trusty W9INN with
a Buckmaster OCF; but the Buckmaster is a subject for another thread.

73, Ed, W6LOL