On Tuesday, January 27, 2015 at 1:59:44 PM UTC-6, Irv Finkleman VE6BP wrote:
I read an article somewhere, likely an antenna book, that you can get
away with short radials on a short loaded antenna as long as they
are at least as long and the antenna is high.

On my tiny 6ft by 10 ft by 10 ft high balcony I plan to deploy a
multiband antenna (by Superantennas) which is center loaded, with an
adjustable loading coil. The antenna when fully extended is
about 9 ft high. I am going to cut and attach about 8 or 10
radials, all about 10 feet long. They will have to be laid in
a relatively random pattern since the antenna will be located
in about the center of the balcony. I cannot have anything
extending or dangling off the balcony.

Once I have those short radials in place, I plan to cover them
with a piece of outdoor carpeting to hold them in place, and in
order that I can still step out on the balcony without disturbing
them or hopelessly entangling myself among them.

In the near future, I have a magnetic loop on order but it will
only cover the bands 20 thru 10M. With the vertical I hope to
operate on all bands, realizing that efficiency will be quite low.

Has anyone encountered the article, or the information supporting
this idea before?

Does anyone have any suggestions which might help with my
continued attempts to RADIATE OR DIE TRYING?

Thanks in advance for any input on this matter.

Irv VE6BP

Normally I would consider that a ground plane, and would prefer
tuned radials, either symmetrically layed out, or multi conductor
ribbon radials like Butternut used to sell.
But if that balcony floor is cement, likely with rebar in it, that
may well de-tune any tuned radials you would lay out.

So I'd probably prefer Jim's chicken wire plate idea in that case.
Would be kind of like an elevated mobile setup..
In such a case, the "plate" should have little effect on the tuning
of the radiator, same as the typical mobile whip when changing vehicle
sizes. So I wouldn't expect to see much change as where the whip is
resonant, when using an un-tuned ground such as that.
But as the ground system gets better, the bandwidth would normally
decrease a bit.

That's how I usually gauge the effectiveness of a ground radial system,
and whether or not extra radials actually helped much or not.
If adding radials decreases bandwidth, they helped.. If not, probably
not so much.
Of course, if you saturate a balcony with mesh, not much you can do to
improve things other than adding a solid round plate around the the
immediate base of the antenna for maximum density. That's where the most
current is, and having a solid round plate might be slightly better
than the mesh right around the base of the radiator. How much, I dunno..
I guess it would depend on the size of the gaps in the mesh used.
I know the amount of metal directly under a mobile whip can be fairly
critical as to the overall efficiency, no matter how well the various
metal pieces are bonded together. The more sheet metal directly under
the whip, the better, by a pretty noticeable amount.

I once installed a mobile whip behind the back window of one of my trucks
on a length of angle iron that was well grounded on both ends as it
attached to the bed sides, and even had grounded braid under it for
extra bonding. It was fairly terrible much to my surprise.. I could tell
the difference right off the bat vs the trunk mounting I had used previous
in a different car.
I then moved it to the side, on top of the much wider plate that was over
the utility bed tool boxes. "The truck has a utility bed, not regular."
It then came back to life in a normal manner. The much wider steel plate
under the antenna made a large difference in efficiency vs the fairly
narrow strip of angle iron, even with it well bonded to the truck.

There was no difference where the whip was resonant, same as I see no
difference between any of the vehicles I've used it on, both small cars,
and large trucks. Which tells me the vehicles act much more like an untuned
ground radial system, than the mirror image of a loaded dipole.
A cement balcony floor with mesh "should" act about the same way.
It should be about like a mobile parked on top of a multi story parking garage.