[Elecraft] Re: Wire Antennas

[Rick Hiller]

Dave (and Don),

Not a silly question, Dave, what so ever.

My suggestion was to open it up 90 degrees from the present feed-point, 1/4
way around...this being a voltage maximum (loop) and current minimum (node).


This enables the loop to still act like a loop on 80, if you desire to
maintain it's present performance.  And then on 160 it acts like, as Don
states, "a folded back 1/2 wave dipole on 160 meters" but in this case it
will be off center fed.   Auto 80/160 band switching, once you get the
lengths correct for the two bands, if that is possible in this case, as I do
not know what modes you operate.

If you open it at, as Don suggests, 180 degrees or half way round, the 80
meter loop turns into a bent 80 meter "2 Half-waves in Phase" with a very
high Z feed, if you maintain the feed point as is.  This also shifts the
standing wave current distribution by 90 degrees, which might cause you
problems if your original antenna was set up to favor a particular area of
the world.  Not convinced that is the case though, as it does sound like you
have up 270 feet of wire in a triangular loop, "cause that's where the trees
be".  Wish I had those trees -- hi.

60 feet above ground is low for a horizontal 160 meter sky hook, but you do
what'cha gotta do.

Sounds like a fun modeling and empirical experiment to say the least.

Regards -- Rick -- W5RH

-------------------------------------------------

Dave,

Open it at the point 180 degrees (midway around) from the feedpoint.  If
your existing loop is a full wavelength on 80 meters, opening it will turn
the loop into a folded back 1/2 wave dipole on 160 meters - not as good as
straight out, but it should work since you are feeding the line with a tuner
anyway.
In fact, you may be able to make it automatic by using a trap tuned to 160
meters - that will electrically open the loop on 160 and only add some
inductnce on the other bands.

73,
Don W3FPR

> -----Original Message-----

>
> Not sure where you are suggesting I open it.  I was considering
> disconnecting the feedline on one side where it connected to the balun.
>   Is this what you mean.  My apologies if it is a silly question.
>
> David Wilburn
> dave.wilburn at verizon.net
>
>
>
> Rick Hiller wrote:
> > Dave,
> >
> > Another possibility for 160 -- Don't know to what extent/effort
> you want to
> > go to get on 160, but here is an easy way, although, a bit of a
> compromise.
> >
> > Simply open the loop at one of the 80 meter voltage loops (also
> a current
> > node).  The 80 meter standing wave current distribution
> /performance will
> > not change, but it will force the wire to be an off center fed 1/2
> > wavelength for 160.  Although not quite resonant within the 160
> meter band,
> > if you feed it with open wire and run it thru the appropriate matching
> > network, you should be right.


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