Roy Lewallen wrote:


An antenna doesn't have a single "radiation angle". It radiates at
all angles. The relevant question is how much does it radiate at the
particular angle of interest, not at which angle does it radiate the
most.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

That's true, except few if any hams have a specific "angle of
interest", since different angles are used at different times. For
most of us, the angle of maximum radiation gives a general indication
of how the antenna will perform. A better indication would be a
graphical representation. It's always a problem when one tries to
reduce a complex situation like this down to a single number.

73, Bill W6WRT

On 13 Sep 2005 20:59:43 -0700, wrote:

Money and space are actually limiting factors, but at least CC&R's
arent! My wife and I have been discussing this, and she really
doesn't like the idea of something 30 to 40 feet high on a small lot.

....excerpted...

I think because space, money, and aesthetics are limiting factors, I
need to use precision to my advantage rather than size or height, and a
4 square may help there.

Comments?

The Eternal Squire

Any reason you're not considering a 20 meter dipole, fed with
ladderline to a tuner, for 20 thru 10 meters? Put it 25 feet high, and
it's nearly or more than a half wave high on all bands.

bob
k5qwg

However, how does that relate to using a shortend antenna with maybe
10% radiation efficientcy to a dipole at a reasonably attainable
height?

Well....Exactly as he described.
An antenna which radiates its maximum at a high angle might well
radiate more at a low angle than an antenna with a lower angle of
maximum radiation.

The thing is "might".... My mobile antenna on 40m is *much* less
efficient than my dipole at 40 ft. But...It still is the best to longer
hauls over about 800 miles, and to dx. In it's case, it does radiate
more at the lower angles I'm using at that time, vs the dipole.
With some lesser mobiles, "mine is fairly stout", this might not be
the case. The best antenna should always be decided to fit the
usual paths to be used. In the case of my mobile vs the dipole, it's
possible that if the dipole were raised another 1/4 wave higher, it
could match the mobile at those lower angles.
At home, I often ran a dipole at 40 ft vs a full size ground plane at
the same height. Both were pretty efficient. Efficiency comparisons
were fairly useless as to actual performance. What really decides
which is best at a given time, is the path, and angles to be used.
Now, if you compare two same length low dipoles, both to NVIS, both
shooting straight up, and one is less lossy than the other as far as
feeding method, etc, then yes, efficiency will decide which one is
best.
MK

A better indication would be a
graphical representation.

The EZNEC demo does that well. There is a little green ball
that you can grab with your mouse, and place it at any angle
you wanna check. Makes it quite easy to see, or compare
various angles. MK

I think because space, money, and aesthetics are limiting factors, I
need to use precision to my advantage rather than size or height, and a
4 square may help there.

Sounds like too much work for my lazy a$$... :/ If you did that for
20m, it's kinda stuck , as far as spacing, etc, for good performance
on the other bands. Me, on 20m...I'd be using my mobile antenna.
And I'd probably be hanging pretty close with any "fancy" antenna.
When I'm mobile, 20m up, there is *no* disadvantage vs being at
the house on dipoles, etc.. At least as far as talking. On 20m, my
mobile is LOUD. I can work dx at the drop of a hat, and still do
well stateside. Even on 40m, there is little real disadvantage to
being mobile vs the dipole at home. Even in the daytime. Say if
I'm 20-30 over 9 at home, and drop to 10-15 over 9 in the mobile.
Doesn't
amount to a hill of beans... Same for 75m. But in the summer on 75m,
I do recommend a dipole/loop, as it will be worth quite a bit in
getting
over the noise running NVIS. I could talk with the mobile just fine,
but the dipole will make me "full quieting" to use an expression...
It's like throwing on an extra 500w when you are shooting upwards...
I wouldn't underestimate how well a *good* mobile antenna could
work on the higher bands. If it's mounted up high on a trailer, etc,
it should work well. It's like being on a huge car. The only problem
is
changing bands...You need to be able to reach it to change taps,
etc.. But that can be easy with a quick disconnect. That's what I
use on mine. I can't reach my coil when the antenna is on the trucks.
With the disconnect, a twist, and it's off. Also good for theft
prevention..
A good screwdriver could be an option too.
Not saying you can't try other antennas, but just saying , a good
mobile
will get the job done, all by itself. And it's pretty simple and easy
to
look at visually. It will often outplay ground mounted trap verticals
with mediocre radial systems on the higher bands.
MK

wrote:
A better indication would be a
graphical representation.

The EZNEC demo does that well. There is a little green ball
that you can grab with your mouse, and place it at any angle
you wanna check. Makes it quite easy to see, or compare
various angles. MK


Better yet, you can superimpose the plots from two antennas for direct
comparison. In v. 4.0, you can even get a numerical readout of the
difference between the two in dB at the angle of the cursor (the little
green ball).

Roy Lewallen, W7EL

wrote:
On Tue, 13 Sep 2005 20:43:23 -0700, Roy Lewallen
wrote:


An antenna doesn't have a single "radiation angle". It radiates at all
angles. The relevant question is how much does it radiate at the
particular angle of interest, not at which angle does it radiate the
most. An antenna which radiates its maximum at a high angle might well
radiate more at a low angle than an antenna with a lower angle of
maximum radiation.

Roy Lewallen, W7EL


Hello Roy,

I do understand that. I also understand when you say radiation angle
your talking about the primary or dominent lobe(s). There may be
many other lobes at useful or less than useful angles present as well.

However, how does that relate to using a shortend antenna with maybe
10% radiation efficientcy to a dipole at a reasonably attainable
height?

Allison
KB1GMX

The context was that one antenna was better for DX than the other
because it had a "lower radiation angle". An antenna with a "low
radiation angle" which is 10% efficient probably radiates less at low
angles than a more efficient antenna with a "high radiation angle".
Therefore it's not a better DX antenna. My point is simply that the
angle of maximum radiation is not a valid criterion for comparing antennas.

Roy Lewallen, W7EL

Bill Turner wrote:
Roy Lewallen wrote:


An antenna doesn't have a single "radiation angle". It radiates at
all angles. The relevant question is how much does it radiate at the
particular angle of interest, not at which angle does it radiate the
most.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

That's true, except few if any hams have a specific "angle of
interest", since different angles are used at different times. For
most of us, the angle of maximum radiation gives a general indication
of how the antenna will perform. A better indication would be a
graphical representation. It's always a problem when one tries to
reduce a complex situation like this down to a single number.

73, Bill W6WRT

I agree, which is why EZNEC produces a graphical output. I encourage
people to look at it rather than reducing the pattern to a single
number. And I have to emphasize once again that what really counts is
the field strength, not the pattern shape. An antenna can have a
wonderful looking pattern with nearly all its radiation at low angles,
and still be a poor antenna for DX. Or with nearly all its radiation at
high angles and be a poor antenna for short range communications. One
familiar example is a Beverage antenna, which has a lovely pattern shape
but makes a poor transmitting antenna. A quarter wave vertical will
nearly always do much better for transmitting, even at the angles
favored by the Beverage.

Roy Lewallen, W7EL

wrote in message
ups.com...
Hi,

I'd like some advice for determining the best antenna to put up in my
situation.

I am getting set to move to a trailer park in northeast arizona, about
50 miles west of Gallup, NM. Locals have no objection to antennas so
long as people don't have to run into them via normal passage ways.
The trailer is 12 feet high by 15 feet wide by 50 feet long, facing
N-S. Nearest certain ground is electrical panel. The water pipe is
metal but could be interrupted throughout system by PVC. There may
also be significant noise from AC systems in park.

Good news is that my wife is giving me an entire walk-in closet for my
station, and that I can lay aluminum foil against all surfaces to
create a Faraday cage.

I have approx 25 to 30 feet between my trailer and neighbors, and a 35
foot altitude streetlamp 6 feet away curb. Soil conductivity is red
clay, extremely poor. Significant rainfall (monsoons) summer to fall.
Winds gusting to 50 or 60 mph during winter. Soil frosts between
October to March.

I would like to work CW DX on 40, 30, 20, and 17 meters. 80 and 160
would
be a bonus. Conventional options such as tower or surplus telephone
pole are out of the question due to cost and lack of available area.
Radials must be buried as children are playing nearby.

Probable options:

1) Load up the streetlamp with an antenna matcher, work against 180
degrees of buried radials out to 1/8 lambda.

2) Solder a series of tin/steel cans (cantenna) using pocket torch and
copper tape to 1/4 lambda with added capacitance hat(s), brace the cans
against the ground and the trailer, work against 270 to 360 degrees of
buried radials out to 3/8 lambda.

3) Create a mast from 40 feet of metal pipe and 15 feet of wood rod,
brace against trailer burying pipe end 10 feet, mount an inverted vee
trap dipole in N-S direction for E-W DX.

4) Pair of masts on either side of the trailer, mount a delta loop
from each mast, feed one loop and use the other as a reflector.

5) Pair of cantennas on each side of the trailer, operating as out of
phase pair of 1/4 lambda verticals.

Which would be best? And where do I place the lightning arrestor(s)?

Thanks,

The Eternal Squire

How about the screwdriver antenna. This is compact, can even be "disguised"
inside a PVC pipe, can be positioned vertically OR horizontally and can be
used to tune a random wire strung into a nearby tree. I used this system on
a motor home where we positioned the antenna on the rear ladder with a
swivel mount. When traveling, the antenna was positioned at a 45 degree
angle and rested in a wooden cradle on top of the bus. At rest, the antenna
could be raised to the vertical in a minute or two and tightened with
thumbscrews. Because the motor home was mostly fiberglass, we quickly
discovered that the antenna could be used in the semi-horizontal position
while going down the road with good results! In your case, your trailer
would be a "mobile", but you could set it up in several ways to take
advantage of various situations, and, also tune a random wire with it. I've
done this while on field exercizes with CAP.

Now I know I am partial since I make screwdrivers, but you can find a
variety of makers on the web. Just try to avoid the ones made of PVC and, of
course, there are those that are SUPER expensive. Go for the ones with
larger diameter coils and wire sizes and avoid the ones that promise 160
thru 10. Those that promise 160 thru 10 are the ones that are wound on
small diameter forms and are wound with 20 gauge wire CLOSELY together (in
effect, transformer-wound) which destroys your "Q".
I doubt seriously such an antenna would do much "punkin" on 160!

Every body runs into compromises at times, so you have to be do the best you
can do with what you have to work with.

If you have 75 feet of room over your lot, then you might visit
www.k1jek.com for an all-band dipole 80-10 Meters. I'm told this is a good
choice for short lots.

Hope this helps

73

Jerry
K4KWH

www.qsl.net/k4kwh

Smack her in the head and put up a tower, It has worked on all 7 of my
wives. :)

wrote in message
oups.com...
Money and space are actually limiting factors, but at least CC&R's
arent! My wife and I have been discussing this, and she really
doesn't like the idea of something 30 to 40 feet high on a small lot.

Her interest actually is gardening and we had been discussing
containing an area of decent topsoil within a square formed by railroad
ties. She has no objection to 20 to 25 foot high metal poles on the
corners of a square 20 to 25 foot on the side... which turns out to be
the core geometry of a 20 meter 4-square broadside phase array.

I would lay the poles first in concrete reinforced holes, connect the
feed network and radials on the dirt, and lay feed line underground
from the array to just near the trailer. Then I would lay the railroad
ties along the square, and then fill the square with topsoil.

Additional radials would need to be buried under a couple inches of red
clay fanning out from the square.

Variations:
1) could I create trap verticals from the poles for 20, 17, 15, and 10
meters, or do I need inscribed squares of seperate verticals because
seperate phased feeds might be needed for these other bands?
2) could I simply operate the square outside of 20 meters with a tuner
for local operation?

I think because space, money, and aesthetics are limiting factors, I
need to use precision to my advantage rather than size or height, and a
4 square may help there.

Comments?

The Eternal Squire