[AMRadio] Re: new antenna and matchbox a bust.


Craig C. Heaton wd8kdg at worldnet.att.net
Tue Jan 30 22:49:52 EST 2007


Craig C. Heaton wrote:
> I give in: if the parts n' pieces raise the contacts you wish to QSO with
so
> be it. Sort of like trying to get some where, different routes all work.
You
> can travel east far enough to get back within two feet of where you
started.
> Easier just to do a 180 and take a step.
>
> Why bother with playing with coax, switching to open wire, etc. Open wire
> all the way is an easy balance situation, no muss, no fuss, and even a
> johnson matchbox with limited range will work, given there is a real
antenna
> connected to the open wire.

I don't think you're understanding what Brett is doing, Craig...

the two coax runs have the center conductors attached to the balun
output of the tuner.  The shields are tied together (and I ass/u/me
grounded).  The run extends from the output of the tuner to the antenna,
where each side of the 100' overall length dipole is connected to each
of the two center conductors on the twin-coax run.

So.... what's not balanced about it?

--
73
-Geoff/W5OMR


As I look at my station, the shields of the few feet of coax that I use to
connect receiver, transmitter, dow-key, etc they are tied together too! All
connect to SO-239's, to each other, and the radios chassis are grounded.
Still unbalanced. Sort of like the antenna described. Apples & bananas but
the shields are tied together. Coax isn't balanced. Nothing to balance the
outside shield. Ask the engineering staff of the company that makes coax,"Is
your coax balanced". I know what the answer will be. But, yes it can be used
in different ways, you could use it to wire all the 120VAC receptacles in
your house too.

Yes, I can see what Brett is trying to do. But why that way. Two runs of
coax,(weight to be suspended in air, shields tied together at the feed point
(places for water to get in and ruin coax). Yes, coax can be used in many
different ways, balun, impedance matching, stubs, etc.

Don, K4KYV, has a good view as to a fix for the issue. Short antennas and/or
the wrong length of feed line are asking for problems. Bretts original post
was for 50 feet of wire on each side of the dipole, feed with 40 feet of
open wire, then 2 RG214 runs to the johnson tuner. " A worse working thing I
ever put up."

Not sure why the switch from open wire to RG214, maybe impedance
matching,,?? Not sure why just 100 feet of wire trying to get on 80 meters.
Not impossible, just not as efficient as a full size antenna. That's why the
suggestion to try a loop. My small city lot will not hold a full size 80
meter dipole either, tried loading coils but they just arc under any power.

But it is fun trying,

Craig,

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