On Oct 15, 6:24*am, Mike Coslo wrote:
On 10/14/10 8:31 PM, Richard Clark wrote:



On Wed, 13 Oct 2010 13:49:31 -0400, Mike *wrote:

I would
like to run a number of wires, maybe 6, to the coil as connections to
taps, and run them at an approximate 90 degree angle to the coil.

Hi Mike,

Run those wires to what? *What length wires?

* * * *Will these wires have much of an effect?

Sure. *Will it matter? *You (the reader who performs this aside from
you, but including you) wouldn't necessarily know where the antenna
would have resonated to begin with, and any change could hardly
surprise you in that regard. *Aside from issues of resonance, we would
consider loss. *As you are running them at 90 degrees (the ambiguity
has me wondering, do they spoke into the coil, or out?), then you are
seeking to avoid wire spacing issues that force Ohmic loss through
proximity. *Given that, loss would seem to be a non-starter. *If the
wires are long (again, the ambiguity of where they go), then they
become part of the radiator, and as such would intercouple. *As the
entire construction is a wild card in resonance, this would not seem
to be problematic anyway. *On the other hand, it could diffuse control
and present some odd tuning characteristics. *This would only add to
the lore and you might be able to call it the Beneficial Coslo Effect
and we are blessed with the BCE 'Tenna (I won't use the full word, as
doing that will depreciate the legendary value). *As we all know, any
new name inherits at least 6dB gain in performance.

Initial idea is to run the separate wires as taps on the coil. I'm
intending to run them on the outside of the coil, probably separated
about an inch away. The wires would then go to a (insert whizbang gadget
here that I'm still figuring out) which then switches taps as needed.
I'll probably start with manual switching. There is also the matter of
that tuning coil at the bottom of the antenna to ground, which varies
between 8 turns of number 12 on a 1.5 inch diameter coil on 75/80
meters, to no coil at all on 20 meters, which is the highest frequency
it will tune at.

The antenna itself is semi-standard bugcatcher, a four foot bottom
section, followed by the six inch coil, (standard GLA systems) followed
by another roughly foot and a half section, then a 16 inch Capacity hat,
then a spring and topped off with a 102 inch whip. Taps at the present
short out the remaining coil below themselves. The whole thing is
mounted on the spare tire holder - the spare resides in the back of the
vehicle while mobiling.

Needless to say, this thing is tall. There is a monofilament line
attached to the top of the antenna with loops at various places, that I
pull and hook around a convenient place in the interior. 50 *pound test
is what saves this antenna from trees, branches, etc. *Since people
can't see the line, the setup *- which as you can imagine gets some
stares to begin with - eyes bug out when it appears to be moving all by
itself. But I digress.

Anyhow, I pretty much assumed that there might be some small tuning
differences on the lower frequencies, but I was just making sure that I
wasn't running the road to perfidy with any hidden "gotchyas" - like if
a stinger goes too far into a loading coil - one of those things that
might not be completely intuitive until after the fact.

* * * * - 73 de Mike N3LI -

Really sounds like you are reinventing the old Swan mobile antennas. I
have an almost new in the box, motor driven unit that has the
switching mechanism just like you are thinking about. The motor in the
bottom unit has a dial-cord wound around it's shaft. The other end of
the coil loop goes over a pulley and a sliding contact is attached to
the dial-cord.

Is this what you are envisioning?

Paul, KD7HB