I'd guess that a brick wall would lower the resonance somewhat (due to
the brick's dielectric constant), but not introduce a significant amount
of loss. But that's a guess.

What I'd do, of course, is model the antenna with EZNEC (the free demo
program would be adequate). That would tell me where the antenna would
be resonant without the brick wall. Any major deviation from that could
be attributed to the brick wall. Of course, you'd have to include your
coil in the model, including its loss if you want to determine the
antenna loss, and the feedline to account for its impedance
transformation and consequent effect on resonance. To determine the
antenna loss I'd look at the bandwidth with EZNEC and compare it to the
measured bandwidth -- if the real antenna is considerably broader,
there's extra loss from somewhere that's not in the model.

If you don't think it's worth the effort to model, you might just try
doubling the distance from the wall and remeasuring. I'm not sure that
would be enough to really tell, but if the resonance changes noticeably,
then the bricks are having an effect. And if the bandwidth decreases
appreciably, then the bricks are contributing loss.

Roy Lewallen, W7EL

Ken Bessler wrote:
What effect would a brick wall have on a HF antenna?
I'm talking 1-2" distance from the bricks, folks. The
wire used is 22 ga stranded insulated speaker wire.
Now no lectures about power - I run QRP. :-) The
station is well grounded to a copper baseboard heater
pipe and all components have short runs (12" or less)
of 1/4" braid line going to a common point. From there
it's 1/4" braid (26" long) to the pipe. I can touch any
part of the system while transmitting and see no change
in SWR.

I cut an inverted V 66'7" per leg 133'2" overall. It's fed
with 12' of rg8x coax with a 6 turn 2-5/8" dia coil at the
feedpoint. The apex of the antenna is roughly 25' up. The
ends of the antenna are at chest height. The antenna is bent
around the corner of my building 90 degrees (I'm in a
corner unit). The last 8' of each leg bends again 90 degrees.

The antenna resonates as follows:
============
2.130 2:1 swr
2.715 1:1 swr (flat)
3.620 2:1 swr
============
8.970 2:1 swr
9.210 1.8:1 swr
9.390 2:1 swr
============
12.230 2:1 swr
13.040 1.9:1 swr
13.850 2:1 swr
============
15.930 2:1 swr
============
20.970 2:1 swr
22.745 1.2:1 swr
24.520 2:1 swr
============

If I figure 468/133.1666666667 I get 3.514.393 mhz
for resonance How come the antenna is so far off?
Could it be the height? Not that I'm complaining - I
like the low resonance and my Z11 autotuner will take
this antenna down to 1.8 mhz real easy. Although at
that freq I expect the antenna will radiate a NVIS
signal due to low HAAT.

Any ideas???

72's de Ken KG0WX

Ken:

I've not run HF measurements on bricks, but I can tell you that a brick wall
is extremely lossy at 1 GHz and above, by measurement. Their water
(dielectric constant = 80) content is relatively high unless recently baked
and sealed, and depending on the particular clay they were fired from, they
are somewhat conductive. So, placing your antenna close is like putting it
next to a high dielectric RF absorber. Not a good choice.

--
Crazy George
Remove NO and SPAM from return address
"Ken Bessler" wrote in message
...
What effect would a brick wall have on a HF antenna?
I'm talking 1-2" distance from the bricks, folks. The
wire used is 22 ga stranded insulated speaker wire.
Now no lectures about power - I run QRP. :-) The
station is well grounded to a copper baseboard heater
pipe and all components have short runs (12" or less)
of 1/4" braid line going to a common point. From there
it's 1/4" braid (26" long) to the pipe. I can touch any
part of the system while transmitting and see no change
in SWR.

I cut an inverted V 66'7" per leg 133'2" overall. It's fed
with 12' of rg8x coax with a 6 turn 2-5/8" dia coil at the
feedpoint. The apex of the antenna is roughly 25' up. The
ends of the antenna are at chest height. The antenna is bent
around the corner of my building 90 degrees (I'm in a
corner unit). The last 8' of each leg bends again 90 degrees.

The antenna resonates as follows:
============
2.130 2:1 swr
2.715 1:1 swr (flat)
3.620 2:1 swr
============
8.970 2:1 swr
9.210 1.8:1 swr
9.390 2:1 swr
============
12.230 2:1 swr
13.040 1.9:1 swr
13.850 2:1 swr
============
15.930 2:1 swr
============
20.970 2:1 swr
22.745 1.2:1 swr
24.520 2:1 swr
============

If I figure 468/133.1666666667 I get 3.514.393 mhz
for resonance How come the antenna is so far off?
Could it be the height? Not that I'm complaining - I
like the low resonance and my Z11 autotuner will take
this antenna down to 1.8 mhz real easy. Although at
that freq I expect the antenna will radiate a NVIS
signal due to low HAAT.

Any ideas???

72's de Ken KG0WX

Hm, woops. My guess that they wouldn't be lossy was based on the
assumption that they don't contain much water. In light of what George
has said, I retract my guess. Putting your antenna close to anything
containing water is bad news from a loss standpoint, as George says.

Roy Lewallen, W7EL

Crazy George wrote:
Ken:

I've not run HF measurements on bricks, but I can tell you that a brick wall
is extremely lossy at 1 GHz and above, by measurement. Their water
(dielectric constant = 80) content is relatively high unless recently baked
and sealed, and depending on the particular clay they were fired from, they
are somewhat conductive. So, placing your antenna close is like putting it
next to a high dielectric RF absorber. Not a good choice.

--
Crazy George

"Roy Lewallen" wrote in message
...
Hm, woops. My guess that they wouldn't be lossy was based on the
assumption that they don't contain much water. In light of what George
has said, I retract my guess. Putting your antenna close to anything
containing water is bad news from a loss standpoint, as George says.

Roy Lewallen, W7EL

Crazy George wrote:
Ken:

I've not run HF measurements on bricks, but I can tell you that a brick
wall
is extremely lossy at 1 GHz and above, by measurement. Their water
(dielectric constant = 80) content is relatively high unless recently
baked
and sealed, and depending on the particular clay they were fired from,
they
are somewhat conductive. So, placing your antenna close is like putting
it
next to a high dielectric RF absorber. Not a good choice.

--
Crazy George


Well, that expains the wide bandwidth between the 2:1 swr points
(1490 khz)......

Still, I am VERY limited as to my options - I rent here - so this
antenna is it or else I go with a Superantennas MP1 stuck out
the window. While the MP1 is a superb performer for it's size,
I don't think it could do any better than what I've got. Then there
is the fact that I'd have to have the window open to make room
for the MP1 - not a good idea in january in colorado.

Now I haven't had a chance yet to see how good the antenna
works on 160 aside from SWR/bandwith weasuring but tonight
on 80 the antenna seemed to hear pretty well - I'm hearing a lot
of 1, 2, 3 & 6 calls all over the band. If the bricks are absorbing
signals they're not doing too much damage. I'm hearing WWVH
on 5 mhz ok, also and I'm hearing a lot of DX AM broadcast
band stations - It's amazing how crowded that band is at 4 am!

Now I do have the option of taking 1 leg and running it away
from the bricks to a nearby tree but the other has to stay where
it is - that leg runs most of it's length about 5' away from the
wall due to the shape of the building. Problem is that the tree
is on the neighbor's property so that's probably out.

Anyways, the performance seems nominal and I don't have
many choices so I guess I'll have to be satisfied with what
I've got.

72's de Ken KG0WX

Ken:

With a short attention span, I'm not sure I understand the tree option you
mention, but if you can run one leg away from the wall, at near a right
angle, then put 2,3, 4 or more wires on the wall and call that your
counterpoise. Feed the wire against that. Picture a ground plane turned on
its side with the driven element running horizontal. That will get most of
the field away from the bricks.

--
Crazy George
Remove NO and SPAM from return address
"Ken Bessler" wrote in message
news

"Roy Lewallen" wrote in message
...
Hm, woops. My guess that they wouldn't be lossy was based on the
assumption that they don't contain much water. In light of what George
has said, I retract my guess. Putting your antenna close to anything
containing water is bad news from a loss standpoint, as George says.

Roy Lewallen, W7EL

Crazy George wrote:
Ken:

I've not run HF measurements on bricks, but I can tell you that a
brick
wall
is extremely lossy at 1 GHz and above, by measurement. Their water
(dielectric constant = 80) content is relatively high unless recently
baked
and sealed, and depending on the particular clay they were fired from,
they
are somewhat conductive. So, placing your antenna close is like
putting
it
next to a high dielectric RF absorber. Not a good choice.

--
Crazy George


Well, that expains the wide bandwidth between the 2:1 swr points
(1490 khz)......

Still, I am VERY limited as to my options - I rent here - so this
antenna is it or else I go with a Superantennas MP1 stuck out
the window. While the MP1 is a superb performer for it's size,
I don't think it could do any better than what I've got. Then there
is the fact that I'd have to have the window open to make room
for the MP1 - not a good idea in january in colorado.

Now I haven't had a chance yet to see how good the antenna
works on 160 aside from SWR/bandwith weasuring but tonight
on 80 the antenna seemed to hear pretty well - I'm hearing a lot
of 1, 2, 3 & 6 calls all over the band. If the bricks are absorbing
signals they're not doing too much damage. I'm hearing WWVH
on 5 mhz ok, also and I'm hearing a lot of DX AM broadcast
band stations - It's amazing how crowded that band is at 4 am!

Now I do have the option of taking 1 leg and running it away
from the bricks to a nearby tree but the other has to stay where
it is - that leg runs most of it's length about 5' away from the
wall due to the shape of the building. Problem is that the tree
is on the neighbor's property so that's probably out.

Anyways, the performance seems nominal and I don't have
many choices so I guess I'll have to be satisfied with what
I've got.

72's de Ken KG0WX

What kind of SWR did you get on frequencies not in your table? I would
expect to see some 10:1 and 30:1 type numbers.

Tam/WB2TT
"Ken Bessler" wrote in message
...

The antenna resonates as follows:
============
2.130 2:1 swr
2.715 1:1 swr (flat)
3.620 2:1 swr
============
8.970 2:1 swr
9.210 1.8:1 swr
9.390 2:1 swr
============
12.230 2:1 swr
13.040 1.9:1 swr
13.850 2:1 swr
============
15.930 2:1 swr
============
20.970 2:1 swr
22.745 1.2:1 swr
24.520 2:1 swr
============

If I figure 468/133.1666666667 I get 3.514.393 mhz
for resonance How come the antenna is so far off?
Could it be the height? Not that I'm complaining - I
like the low resonance and my Z11 autotuner will take
this antenna down to 1.8 mhz real easy. Although at
that freq I expect the antenna will radiate a NVIS
signal due to low HAAT.

Any ideas???

72's de Ken KG0WX

"Tarmo Tammaru" wrote in message
...
What kind of SWR did you get on frequencies not in your table? I would
expect to see some 10:1 and 30:1 type numbers.

My only current way to measure SWR is with a bridge and a low
power transmitter. The limit of this device is 5:1. At times, the SWR
inicated 4-4.5:1 but never higher......

I've since added 10' to each leg and here are the latest numbers:

2:1 swr bandwidth and resonance points:
1.990 - 2.640, 1:1 @ 2.330 mhz (was 2.715)
minor dip to 2:1 @ 8.070 mhz
11.680 - 14.390, 1.2:1 @ 13.610 mhz
21.630 - 25.250, 1.2:1 @ 23.640 mhz

Total antenna length 153'2" (76'7" per leg)

73's de Ken KG0WX

Ken Bessler wrote:

What effect would a brick wall have on a HF antenna?
I'm talking 1-2" distance from the bricks, folks. The
wire used is 22 ga stranded insulated speaker wire.
Now no lectures about power - I run QRP. :-) The
station is well grounded to a copper baseboard heater
pipe and all components have short runs (12" or less)
of 1/4" braid line going to a common point. From there
it's 1/4" braid (26" long) to the pipe. I can touch any
part of the system while transmitting and see no change
in SWR.

I cut an inverted V 66'7" per leg 133'2" overall. It's fed
with 12' of rg8x coax with a 6 turn 2-5/8" dia coil at the
feedpoint. The apex of the antenna is roughly 25' up. The
ends of the antenna are at chest height. The antenna is bent
around the corner of my building 90 degrees (I'm in a
corner unit). The last 8' of each leg bends again 90 degrees.

The antenna resonates as follows:
============
2.130 2:1 swr
2.715 1:1 swr (flat)
3.620 2:1 swr
============
8.970 2:1 swr
9.210 1.8:1 swr
9.390 2:1 swr
============
12.230 2:1 swr
13.040 1.9:1 swr
13.850 2:1 swr
============
15.930 2:1 swr
============
20.970 2:1 swr
22.745 1.2:1 swr
24.520 2:1 swr
============

If I figure 468/133.1666666667 I get 3.514.393 mhz
for resonance How come the antenna is so far off?
Could it be the height? Not that I'm complaining - I
like the low resonance and my Z11 autotuner will take
this antenna down to 1.8 mhz real easy. Although at
that freq I expect the antenna will radiate a NVIS
signal due to low HAAT.

Any ideas???

72's de Ken KG0WX

I used to run a 40M dipole which lay along a rock wall 3 feet
off the ground. I cut it for the center of the band, laid it
out (held in place with a few bricks), and worked the world!

It was just a few bricks short of a full load! Seriously, though,
it worked well.
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/
Visit my very special website at http://members.shaw.ca/finkirv4/
Visit my CFSRS/CFIOG ONLINE OLDTIMERS website at http://members.shaw.ca/finkirv5/
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

On Thu, 21 Aug 2003 17:14:33 -0600, "Ken Bessler"
wrote:

What effect would a brick wall have on a HF antenna?
I'm talking 1-2" distance from the bricks, folks. The

Remember too that many brick walls use steel reinforcement, or lots of
steel strips to hold them to the frame structure unless we are talking
a "real" brick wall which is seldom found in the US in buildings much
less than a century old.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)