[Elecraft] Slinky Question

[Mike McCoy]

>
> >        2. Does anyone have experience with a slinky antenna?
>
> Slinkys are not the most effective way to shorten an antenna.

I agree that 'slinkys' are not the best antenna. I have one in my attic and
it was pitiful. Nothing I did would make it resonate in any amateur band. I
finally got tired of crawling in/out of my attic so I just streteched it as
far as it would go and hooked it up to my SWL receiver as a 'listening'
antenna. Unfortunately it doesn't perform that well in that role either.
It's better than nothing I suppose.

> If you need to
> make a dipole shorter than 1/2 wl one good way to do it would be to use
'linear
> loading':
>
>    ------------------------+   +-----------------------
>              +-------------+   +------------+
>              +------------->   <------------+
>                          feedpoint
>
> You can make the folded sections out of ladder line.
>

I just tried building such an antenna out of 450 ohm 'windowpane' ladderline
per the above and it doesn't work as designed/expected either. I fed the
center matched to some RG8X with a 4:1 balun, insulated the ends (at the
middle) of the 'top' wires and shorted the far ends. I cut it for 40 mtrs
(about 33' overall) and it worked best on 17mtrs (1.4:1 SWR)! Thing is, I
could have hung a simple 17 mtr dipole and it would have been shorter ;)
Then after using it for a couple days for some odd/unexpected/unexplained
reason I haven't figured out the SWR suddenly jumped to 4:1 so I took it
down.

The lesson I (think I) learned was if you are going to make a folded dipole
the wires need to be at least 6-8" apart (and not the 1" or so of 450 ohm
'windowpane' type ladderline). Maybe *true* wire ladderline (not the plastic
variety) might work. I plan to experiment some more soon as I get my hands
on some.

73,
Mike K5PU