To determine the horizontal wire current, download the free EZNEC demo
from http://eznec.com. That's exactly the kind of thing it's good for.

If you put a single horizontal wire out to make an L shape, the wire
radiates a considerable amount. Being as low as it is, a lot of the
power will be dissipated in the ground, and only a small fraction will
be radiated at a low elevation angle. But if you connect to the center
of a horizontal wire to make a T shape, the fields from the two halves
of the horizontal wire will nearly cancel, so it'll radiate very little.
Its main effect, like a capacitive top hat, will be to even out the
current in your vertical wire, which will raise the radiation resistance
and therefore the efficiency.

EZNEC or a similar program will quickly show you the differences in
field strength in various directions for the antenna as it is, and with
either of the top loading configurations.

Roy Lewallen, W7EL

dansawyeror wrote:
Roy,

Thanks. This might be feasible. The site would support 50 foot wire from
the tip. At 500 watts what would the current in the horizontal leg be?
In other words what is the minimum effective gage?

What is the purpose of this leg? Is it capacitive or does it begin to
look like something else. What are it directional characteristics?
Dipoles nodes are perpendicular while long wire nodes are parallel.

Dan

Roy Lewallen wrote:

Frank wrote:

. . .
I agree with comments about adding a horizontal wire to the top of
the vertical; it will probably be easier than a capacity hat. I am
overloaded with work at the moment, but would like to attempt a model
in a week or so when I have less work.



Take a look also at a tee type arrangement. That is, a horizontal wire
with the tip of the vertical connected at or near its center. It might
have some advantages over connecting the wire's end to the vertical.
But of course it might be more involved to construct.

Roy Lewallen, W7EL

Now that is interesting, Roy. I was going to put up a 160 m inverted L this
summer. I am limited to only being able to go up about 45 feet, so I would
need about another 90 feet horizontal.

Are you suggesting that it might be a better arrangement to go up the 45'
and then put up the top "T"? If so, roughly how long should the top part of
the T be (each side of center) to get me to 160? I'm guessing it may not be
accomplished without some base loading...and that is what took me to the
Inverted L in the first place...direct coax feed, albeit not a particularly
good low angle radiator.

I am prepared to put down a radial field...but I want to stick with a simple
vertical wire, either extended horizontally as an Inverted L or as you
suggest, a T, if it can be done. I have about 100' either side of center
available to construct the top part of the T. In either case, the top
loading wires will need to be somewhat of the inverted v construction, as I
don't have 45' high supports for each end.

Thanks for any thoughts you might have. I need to get something done before
winter!

73,

....hasan, N0AN

"Roy Lewallen" wrote in message
...
To determine the horizontal wire current, download the free EZNEC demo
from http://eznec.com. That's exactly the kind of thing it's good for.

If you put a single horizontal wire out to make an L shape, the wire
radiates a considerable amount. Being as low as it is, a lot of the power
will be dissipated in the ground, and only a small fraction will be
radiated at a low elevation angle. But if you connect to the center of a
horizontal wire to make a T shape, the fields from the two halves of the
horizontal wire will nearly cancel, so it'll radiate very little. Its main
effect, like a capacitive top hat, will be to even out the current in your
vertical wire, which will raise the radiation resistance and therefore the
efficiency.

EZNEC or a similar program will quickly show you the differences in field
strength in various directions for the antenna as it is, and with either
of the top loading configurations.

Roy Lewallen, W7EL

dansawyeror wrote:
Roy,

Thanks. This might be feasible. The site would support 50 foot wire from
the tip. At 500 watts what would the current in the horizontal leg be? In
other words what is the minimum effective gage?

What is the purpose of this leg? Is it capacitive or does it begin to
look like something else. What are it directional characteristics?
Dipoles nodes are perpendicular while long wire nodes are parallel.

Dan

Roy Lewallen wrote:

Frank wrote:

. . .
I agree with comments about adding a horizontal wire to the top of the
vertical; it will probably be easier than a capacity hat. I am
overloaded with work at the moment, but would like to attempt a model
in a week or so when I have less work.



Take a look also at a tee type arrangement. That is, a horizontal wire
with the tip of the vertical connected at or near its center. It might
have some advantages over connecting the wire's end to the vertical. But
of course it might be more involved to construct.

Roy Lewallen, W7EL

hasan schiers wrote:
Now that is interesting, Roy. I was going to put up a 160 m inverted L this
summer. I am limited to only being able to go up about 45 feet, so I would
need about another 90 feet horizontal.

Are you suggesting that it might be a better arrangement to go up the 45'
and then put up the top "T"?

It might be. You might benefit from the radiation from the horizontal
portion of an L, and you might not. But if it's quite low, the radiation
will be mostly straight up, and a fair amount will be expended warming
up the ground. Neither will occur with a T.

If so, roughly how long should the top part of
the T be (each side of center) to get me to 160?

That's just what antenna modeling programs are for! Dust off your EZNEC
and you'll have the answer in minutes.

. . .

Roy Lewallen, W7EL

Roy,

Is there an EZNEC howto. I have tried to use the demo a few times and can't seem
to get started. I tried to model a simple dipole and a center loaded vertical
and got very lost.

Thanks,
Dan

Roy Lewallen wrote:
hasan schiers wrote:

Now that is interesting, Roy. I was going to put up a 160 m inverted L
this summer. I am limited to only being able to go up about 45 feet,
so I would need about another 90 feet horizontal.

Are you suggesting that it might be a better arrangement to go up the
45' and then put up the top "T"?


It might be. You might benefit from the radiation from the horizontal
portion of an L, and you might not. But if it's quite low, the radiation
will be mostly straight up, and a fair amount will be expended warming
up the ground. Neither will occur with a T.

If so, roughly how long should the top part of the T be (each side of
center) to get me to 160?


That's just what antenna modeling programs are for! Dust off your EZNEC
and you'll have the answer in minutes.

. . .

Roy Lewallen, W7EL

On Thu, 25 Aug 2005 19:15:13 -0700, dansawyeror
wrote:

Is there an EZNEC howto. I have tried to use the demo a few times and can't seem
to get started. I tried to model a simple dipole and a center loaded vertical
and got very lost.

Hi Dan,

It would be far simpler to hit the "Open" button and select an already
existing example of an antenna and see where that goes.

73's
Richard Clark, KB7QHC

On Thu, 25 Aug 2005 19:15:13 -0700, dansawyeror
wrote:

Is there an EZNEC howto. I have tried to use the demo a few times and can't seem
to get started. I tried to model a simple dipole and a center loaded vertical
and got very lost.

Perchance have you happen to read the help file?

Hint; that information is there.

Danny, K6MHE

dansawyeror wrote:
Roy,

Is there an EZNEC howto. I have tried to use the demo a few times and
can't seem to get started. I tried to model a simple dipole and a center
loaded vertical and got very lost.

In the main window, click Help, then Contents. This is the EZNEC manual.
Read the Getting Started section, and go through the "Test Drive"
tutorial it directs you to. That should get you started.

Roy Lewallen, W7EL

I bought EZNEC +,v4 and enrolled in the ARRL antenna course. With my
many years of experience (bad & good!) I knew it was unlikely I would
really get much out of either....

It has turned into one of the best educational bargains I have ever
encountered. I am less than halfway through the course and find my
biggest problem is that I keep running off in all directions to check
out my past antenna failures.

My wounded ego is healing nicely and I am satisfied that I am no
antenna expert. I am a perpetual antenna student!

On Thu, 25 Aug 2005 19:15:13 -0700, dansawyeror
wrote:

Roy,

Is there an EZNEC howto. I have tried to use the demo a few times and can't seem
to get started. I tried to model a simple dipole and a center loaded vertical
and got very lost.

Thanks,
Dan

John Ferrell wrote:
. . .
I am a perpetual antenna student!

And so are we all.

Roy Lewallen, W7EL

I found the error, I had to fix two conditions that I had changed in the
model:

Copper wire (for loss)
Ground characteristics

Now that both antennas have the same conditions, the T has ever so slightly
better gain at 20 degrees than the Inverted L. Not enough to bother with the
increased complexity, and the input Z is now down around 5 ohms for the T
and 8 ohms for the L.

Now, is it worth matching the 8 ohms up to 50 at the feedpoint, or just
using the tuner in the shack to take care of it? (coax feed, LMR-400, about
50')

....hasan, N0AN

"Roy Lewallen" wrote in message
...
John Ferrell wrote:
. . .
I am a perpetual antenna student!

And so are we all.

Roy Lewallen, W7EL