John:
To determine operating height you need to know: what the intended
operating frequency range, the size of the loop and the operational area
you wish to communicate with. Also if you will be operating on multiple
bands, square loops have phasing problems on even harmonics. For NVIS
to 400 to 600 mile radius on multiple bands the Double Delta at 30' is
optimum for 1.8 Mhz to 15 Mhz continuous and has gain over a one wave
length loop. During field day operations I use my portable DD Loop at
16" and was using a SG2020 with 20 watts. There were less than a dozen
stations which I heard which I could not work. And I was working
stations the rest of the group on the mountain could not hear on their
rig/antenna setups. Rough dimensions for the DD Loop are 150' x 80'
with 500' of radiating wire fed with ladder line to a transmatch. I
however use a 1:1 w2du balun and rg8-x in the portable setup to a
Dentron Monitor Jr. transmatch. The layout of the DD Loop can be
altered BUT you MUST use a design program as little as a foot or two of
spacing change can alter the phasing dramatically. The feed point
impedances vary all over the map when used over a wide frequency range.
I use mine on both ham and non ham frequencies. SO... open ladder line
is best for long runs. Keep Coax short if you are using power! And, a
transmatch is a must.
Overall the DD Loop on 1.8 to 15 Mhz should not be lower than 16' as the
gain drops dramatically. However as we all know use what you can get
away with and what will do the job.
PS: I do a lot of HF Emcomm field work/design here in the state of Oregon
Also if you are trying to do DX with a horizontal loop ... different story.
I hope this helps.
Michael
John Geiger wrote:
> How high does a horizontal loop (the look skywire) need to be for decent
> performance? A quick google search revealed that people were running them at
> 25 or 30 feet with good results (in their opinion). I know that high is
> better, but how high does it need to be to show real improvement over a
> dipole?
>
> 73s John AA5JG
>
>
>
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