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

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.

Since you plan on covering the wires anyway, you might concider looking
for cheap chicken wire to cover the entire deck, which at HF will look
like a solid metal plate.

Also, after you connect the antenna ground to whatever you wind up with,
check the SWR then add a second temporary connection and recheck the SWR.

If the second connection makes a difference, make it permanent and repeat
until additional connections make no difference.

I have a backyard vertical with all the radials tied to a common plate
with the plate tied to the antenna ground. There was a significant
difference on the upper HF bands between one and two tie wires, no change
with three. Even a straight wire has inductance...


--
Jim Pennino

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.

wrote:


(snipped for brevity)
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.

Good idea Jim, especially reinforced by Mark's opinion. The floor is
concrete so I'd expect it to have some rebar in there. I'll check and
see what I can get. I'll also see if copper screen is available. It
might be a little better than the chicken wire, and easier on the
rubberlike deck coating they have over the cement.
Thanks for both inputs.

Irv VE6BP

wrote in message
...
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.

The vehicle acts more like a capacitor to couple to the ground instead of a
radial system.

On Tuesday, January 27, 2015 at 6:46:43 PM UTC-6, Ralph Mowery wrote:
wrote in message
...
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.

The vehicle acts more like a capacitor to couple to the ground instead of a
radial system.

Yep. The reason I mention this is some claim the the typical
mobile system acts more like a dipole, with the whip as one
half of an element, and the car body the other. But in actual
operation, I've never noticed this to be the case.
It acts the same as the typical ground mounted vertical.

If it did act like a perverted dipole, switching to a different
size car, or even on different parts of the same car would cause
a drastic change in the resonant freq. But that has never been
the case with the various mobile systems I've run.
I've run several different mobiles with the same whip, from a small
Honda Accord, to large Ford trucks, and I've never had to adjust the
loading coil setting for any of them. The only difference is varying
levels of efficiency per the size of the vehicle, and the location
of the whip on the vehicle. The best performer is the Ford truck I
have that has a ball mount on the upper roof pillar of the cab.
It's a bit better than the other truck with the utility box mount.
All the cars had trunk mounts, and they were pretty good overall.
A good bit of metal under the whip. I used drilled hole mounts on
those. I've never used any kind of magnet mount. Both trunk mounts had
to be reinforced under the trunk lid with steel plates to take the
abuse of the fairly tall HF whips, even though I was using fairly light
"plastic bugcatchers". Still lots of rocking motion that will distort
the metal of the trunk lid pretty fast if you don't.

Irv Finkleman VE6BP wrote:
wrote:


(snipped for brevity)
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.

Good idea Jim, especially reinforced by Mark's opinion. The floor is
concrete so I'd expect it to have some rebar in there. I'll check and
see what I can get. I'll also see if copper screen is available. It
might be a little better than the chicken wire, and easier on the
rubberlike deck coating they have over the cement.
Thanks for both inputs.

Irv VE6BP

One other point; there will likely be a lot of RF on your coax shield,
so a choke of some sort will be a good idea.


--
Jim Pennino

wrote:
Irv Finkleman VE6BP wrote:
wrote:


(snipped for brevity)
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.

Good idea Jim, especially reinforced by Mark's opinion. The floor is
concrete so I'd expect it to have some rebar in there. I'll check and
see what I can get. I'll also see if copper screen is available. It
might be a little better than the chicken wire, and easier on the
rubberlike deck coating they have over the cement.
Thanks for both inputs.

Irv VE6BP

One other point; there will likely be a lot of RF on your coax shield,
so a choke of some sort will be a good idea.


I'll do that for sure. Thanks for the tip!

Irv VE6BP