I live in a two-story slab house with aluminum siding on the walls. Has
anyone had any experience with mounting an external transmitting loop
antenna (for 80 or 160 m) near aluminum siding? I am guessing it is not
recommended, but I would be interested in any comments about this topic.

John N9JG wrote:
I live in a two-story slab house with aluminum siding on the walls. Has
anyone had any experience with mounting an external transmitting loop
antenna (for 80 or 160 m) near aluminum siding? I am guessing it is not
recommended, but I would be interested in any comments about this topic.

Hi John, Since it is not recommended to mount a loop antenna or any
other kind, near aluminum siding, I doubt many here have done so. May
not get comments about doing the undesirable.
On the other hand, a 160m full wave loop will be so large in
comparison to the small section that is in proximity to the aluminum
siding, you may not be able to tell much difference whether the siding
is there or not. Same thing with a full wave 80m loop. I would go for
it.
Gary N4AST

Thanks for your comments, but a full-wave loop antenna is much larger than I
had in mind. The ARRL Antenna Book contains a write-up about a loop antenna
that is 100 feet in total length. It is built in the shape of an octagon
with 3/4" copper pipe, and contains a capacitor in series with the side
directly opposite the fed side. The loop is mounted with its plane vertical,
and the fed side perhaps a foot off the ground so the lawn mower can go
under it. The capacitor has to be tuned remotely and has to have a rather
large voltage rating. The article implies the antenna has a 2:1 tuning
range.

An alternative one-band antenna is the DLM antenna and might be worth
trying. See
http://www.uri.edu/news/vincent/boxboro_files/frame.htm

wrote in message
ps.com...

John N9JG wrote:
I live in a two-story slab house with aluminum siding on the walls. Has
anyone had any experience with mounting an external transmitting loop
antenna (for 80 or 160 m) near aluminum siding? I am guessing it is not
recommended, but I would be interested in any comments about this topic.

Hi John, Since it is not recommended to mount a loop antenna or any
other kind, near aluminum siding, I doubt many here have done so. May
not get comments about doing the undesirable.
On the other hand, a 160m full wave loop will be so large in
comparison to the small section that is in proximity to the aluminum
siding, you may not be able to tell much difference whether the siding
is there or not. Same thing with a full wave 80m loop. I would go for
it.
Gary N4AST

John,
For what it's worth (not much), I used to run a 1/2 wave dipole
over a metal roof. It worked. The input impedance was reasonable,
certainly not the best, but reasonable. Your loop wuold show some
directionality, I would think, but that may/may not be 'bad', and
the input impedance ought to be adjustable with the capacitor, sort
of, maybe. Also ran a full wave 80 meter loop around a building
with aluminum siding. Had pretty fair clearance all around, so didn't
really affect things much (I'm sure it did, but it worked so who
cared?). Give it a shot, see what happens, then tell us!
'Doc

Thanks for your encouragement.

"'Doc" wrote in message
. ..
John,
For what it's worth (not much), I used to run a 1/2 wave dipole
over a metal roof. It worked. The input impedance was reasonable,
certainly not the best, but reasonable. Your loop wuold show some
directionality, I would think, but that may/may not be 'bad', and
the input impedance ought to be adjustable with the capacitor, sort
of, maybe. Also ran a full wave 80 meter loop around a building
with aluminum siding. Had pretty fair clearance all around, so didn't
really affect things much (I'm sure it did, but it worked so who
cared?). Give it a shot, see what happens, then tell us!
'Doc

From your description the antenna is a 100-foot-perimeter magloop for
160 and 80 meters. With a 3/4" diameter conductor it will do fine.

Provided it is not facing and very near to the side of the house it
should tune up and work OK. Have the plane of the loop at
right-angles to the siding, NOT parallel to it. If you can't manage
this then don't bother erecting it.

I would not like to see the edge of the loop any nearer to the siding
than 1/4 or 1/5 of its diameter. (Apparently it is intended to work
within a few feet of the ground.)

Aluminium is a good conductor, nearly as good as copper. Negligible
loss will be induced in it. Most loss will be in the ground by virtue
of its very low height. The close proximity to ground will also cause
unoticeable detuning.

The presence of the siding will slightly detune the antenna but you
will not notice the difference because there is no way to make a
comparison. But if there is an intermittent contact between the
siding and other walls or metal roof of the house you can expect
trouble. Magloops are VERY sharply tuned!

The radiation pattern may be considerably different from normal. But
again, you will not be aware of it. The broad lobe in one direction in
the plane of the loop may be stronger at the expense of the opposite
direction towards the house.

I have myself run a near-to-ground 160-meter magloop very near to the
brick wall of the house and experienced the detuning which I assume
was due to being adjacent to internal domestic plumbing and house
wiring. The effect disappears when the loop is half its diameter away
from foreign conductors.

The performance of your proposed loop in normal surroundings can be
investigated by easy-to-use program MAGLOOP4 which can be downloaded
from the website below.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

==========================================

"John N9JG" wrote in message
...
Thanks for your comments, but a full-wave loop antenna is much
larger than I
had in mind. The ARRL Antenna Book contains a write-up about a loop
antenna
that is 100 feet in total length. It is built in the shape of an
octagon
with 3/4" copper pipe, and contains a capacitor in series with the
side
directly opposite the fed side. The loop is mounted with its plane
vertical,
and the fed side perhaps a foot off the ground so the lawn mower can
go
under it. The capacitor has to be tuned remotely and has to have a
rather
large voltage rating. The article implies the antenna has a 2:1
tuning
range.

An alternative one-band antenna is the DLM antenna and might be
worth
trying. See
http://www.uri.edu/news/vincent/boxboro_files/frame.htm

wrote in message
ps.com...

John N9JG wrote:
I live in a two-story slab house with aluminum siding on the
walls. Has
anyone had any experience with mounting an external transmitting
loop
antenna (for 80 or 160 m) near aluminum siding? I am guessing it
is not
recommended, but I would be interested in any comments about this
topic.

Hi John, Since it is not recommended to mount a loop antenna or
any
other kind, near aluminum siding, I doubt many here have done so.
May
not get comments about doing the undesirable.
On the other hand, a 160m full wave loop will be so large in
comparison to the small section that is in proximity to the
aluminum
siding, you may not be able to tell much difference whether the
siding
is there or not. Same thing with a full wave 80m loop. I would
go for
it.
Gary N4AST

I appreciate your comments very much; clearly you have had a lot of
experience with antennas. There was one question in my mind about aluminum
siding in contrast to plain aluminum; it is my impression that aluminum
siding is anodized, and anodized aluminum is an insulator. If my impression
is correct, would that make any difference in the interaction between a loop
and the siding?

"Reg Edwards" wrote in message
...

Aluminium is a good conductor, nearly as good as copper. Negligible
loss will be induced in it. Most loss will be in the ground by virtue
of its very low height. The close proximity to ground will also cause
unoticeable detuning.

Only the surface anodizing is an insulator. Radio frequency-wise, it
may just as well not be there leaving the high conductivity aluminium
siding to behave as if the anodizing didn't exist.

If the siding was covered with a 3" layer of plastic it still wouldn't
make any difference.
----
Reg, G4FGQ

=================================

"John N9JG" wrote in message
...
I appreciate your comments very much; clearly you have had a lot of
experience with antennas. There was one question in my mind about
aluminum
siding in contrast to plain aluminum; it is my impression that
aluminum
siding is anodized, and anodized aluminum is an insulator. If my
impression
is correct, would that make any difference in the interaction
between a loop
and the siding?

"Reg Edwards" wrote in message
...

Aluminium is a good conductor, nearly as good as copper.
Negligible
loss will be induced in it. Most loss will be in the ground by
virtue
of its very low height. The close proximity to ground will also
cause
unoticeable detuning.

Excellent reasoning - I guess I should have thought about how enameled
copper wire makes an excellent radiator.

"Reg Edwards" wrote in message
...
Only the surface anodizing is an insulator. Radio frequency-wise, it
may just as well not be there leaving the high conductivity aluminium
siding to behave as if the anodizing didn't exist.

If the siding was covered with a 3" layer of plastic it still wouldn't
make any difference.
----
Reg, G4FGQ

=================================