How to model the house
 

I've read a lot about modeling antennas and ground. But what about the
house? Dipole configurations might look like this.

----------------------------------+
| |
| |
\ W
\ / \
\ / \
------------| |
| |
---------------------------------------

Or this


-------------------------------------
|
|
W
/ \
/ \
| |
| |
--------------------------------------

Or even this

__ ^__
___/ | \___
___/ | \___
__/ W \__
__/ / \ \__
/ \
| |
| |
-----------------------------------

(ASCII art looks better in a monospace font)

The house probably makes a lot of difference to gain and pattern, and
also for other antenna types.

Modeling the house as part of ground might make sense, but there will
be lots of differences. Metal roof and sidings would turn the house
into a faraday cage. A wood frame house with no wiring and plumbing
may be almost like air.

Has anybody included buildings in their models, and have they checked
if this made the model more realistic. Any rule of thumb parameters?

Jon Kåre - LA4RT

Hi,

I do not know nobody who has included the building in the formula. It should
be interesting to get a report about it and I should be curious to get the
opinion of a telecom engineer or to see any radiation pattern with/without
building included.

Possible configurations are of course infinite. You can always replace any
object, car, house, etc, by a special configuration of selfs and caps.
Harder is to find the correct values... The only solution is to experiment
in the field with a meter as two house are never built the same way.

All depend first of the working frequency and then of the height of the
antenna above the object.
Over 1/6 lambda or so over/away from the house I am not sure that the object
will much influence your radiation pattern. Theoretically it does, in
practice this is another affair : could you hear this difference ?...
Then there is the problem of radiations transmitted by your home devices
too, from TV to boilder, TL and other old remote controller that could
surely more bothering that your "house" seen as a whole as they can transmit
RFI at some frequencies in ham bands.

Even with a dipole placed in inverted V the high point on top of the
chimney, the wire tilted at 45 deg like this,

!chimney
/ !
wire/ ! house wall

I know many OM that get excellent results, even in pile-ups (with patience)
as the antenna is somewhat directive and help a bit. They do not care about
the pattern, they practice, and they see that their "small antenna" perform
well. All the more when we know that this is the first third of the antenna
(close to the center feed point and thus from the chimney) that radiates and
much less the ends.

On the other side I know some OM that have erected their beam over
apple/cherry trees, they have never complained about any loss of power or
difficulties to work any entity.

If the problem exists well, its influence must be relativised.

Thierry, ON4SKY
http://www.astrosurf.com/lombry/menu-qsl.htm


"Jon Kåre Hellan" wrote in message
...
I've read a lot about modeling antennas and ground. But what about the
house? Dipole configurations might look like this.

----------------------------------+
| |
| |
\ W
\ / \
\ / \
--------| |
| |
---------------------------------------

Or this


-------------------------------------
|
|
W
/ \
/ \
| |
| |
--------------------------------------

Or even this

__ ^__
___/ | \___
___/ | \___
__/ W \__
__/ / \ \__
/ \
| |
| |
-----------------------------------

(ASCII art looks better in a monospace font)

The house probably makes a lot of difference to gain and pattern, and
also for other antenna types.

Modeling the house as part of ground might make sense, but there will
be lots of differences. Metal roof and sidings would turn the house
into a faraday cage. A wood frame house with no wiring and plumbing
may be almost like air.

Has anybody included buildings in their models, and have they checked
if this made the model more realistic. Any rule of thumb parameters?

Jon Kåre - LA4RT

The house probably makes a lot of difference to gain and pattern, and
also for other antenna types.

Modeling the house as part of ground might make sense, but there will
be lots of differences. Metal roof and sidings would turn the house
into a faraday cage. A wood frame house with no wiring and plumbing
may be almost like air.


Not that simple, like siding, is it RF connection tight or insulated slabs?
Millions of other questions, like you AC wiring, plumbing, coathangers, etc. If
you manage to model it, what are you going to do about it? Level it? :-)

We know houses are bad for antennas, sources of distortion and interference
from and to. If you are serious about serious antennas, you keep them away from
the houses. If you worry about dipole over the house, don't. Just put it up and
enjoy it. Modeling it won't help anything.

Modeling mobile antenna over particular type of vehicle can give us clues about
efficiency and pattern, but measuring it will be more accurate, consider the
current distribution in the loading coil and other effects in a real life time.


So if you worry about Inv Vee or dipole, just keep the ends as far away from
your appliances to minimize the RFI TVI. On HF don't worry about stupid silly
and irrelevant "RF Exposure Guidlines" on HF with typical ham setup.

73 Yuri, www.K3BU.us
www.computeradio.us - budding home of "Dream Radio One"

On Wed, 28 Apr 2004 13:04:09 +0200, Jon Kåre Hellan
wrote:

I've read a lot about modeling antennas and ground. But what about the
house?

Most people use an interior decorator to model their house ;-)

Larry VE7EA
***************
remove "fake" from email address

Yuri, K3BU wrote:
"---consider the current distribution in the loading coil and other
effects in a real life time (and place)."

"Yuri previously said:
"I ordered the 19th edition of ARRL Antenna Book and followed chain of
references that led to information on page 16-7 and Fig. 9 and 10."

These are current distribution diagrams. Formulas exist for these. Can
you write a formula to describe your house? If so, would it also
describe my house?

Best regards, Richard Harrison, KB5WZI

On Wed, 28 Apr 2004 13:04:09 +0200, Jon Kåre Hellan
wrote:
I've read a lot about modeling antennas and ground. But what about the
house? Dipole configurations might look like this.

Hi Jon,

This is actually far simpler than others would have us believe.

Model the antenna you have above/near the house. Model it in the
conventional way (no house) while taking care to include the usual
loss (copper loss, ground loss).

Now measure your antenna's characteristics.

Subtract Measured results from Modeled results = House effects

There's your model for the future. And it's accurate. This beats all
the tea leaf reading and gazing into Xtal Balls to achieve a mystic
answer.

73's
Richard Clark, KB7QHC