Can someone explain to me how a new antenna design is started. Do you
take an initial standard design and then enter it into a modeling
program and optimize it for the required parameters ?

Is there a suitable reference book that would explain this process. I am
thinking about the Cebik antenna modeling book but think this may only
cover how to model and change an existing design,would it cover how to
come up with the initial design in the first place ?

Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm
diameter elements.

Is there a standard formula that would be used to calculate initial
lengths and distances between elements. Then you enter this design into
say EZNEC and use the optimizer to tweak the design.

Thanks in advance

Regards

David

A very good source of starting designs is _Yagi Antenna Design_ by James
Lawson, W2PV, published by the ARRL. It clearly illustrates the various
tradeoffs which can be made in Yagi design, and gives lots of
alternatives. There is no "ideal" design, since there are so many
tradeoffs to be made -- gain, front/back ratio, bandwidth, size, which
you can't maximize all at once.

EZNEC doesn't have an optimizer -- if you use EZNEC you have to tweak
the design yourself. People who have used optimizing programs have told
me they've often been able to improve on the "optimized" design by hand
tweaking with EZNEC.

Roy Lewallen, W7EL

David wrote:
Can someone explain to me how a new antenna design is started. Do you
take an initial standard design and then enter it into a modeling
program and optimize it for the required parameters ?

Is there a suitable reference book that would explain this process. I am
thinking about the Cebik antenna modeling book but think this may only
cover how to model and change an existing design,would it cover how to
come up with the initial design in the first place ?

Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm
diameter elements.

Is there a standard formula that would be used to calculate initial
lengths and distances between elements. Then you enter this design into
say EZNEC and use the optimizer to tweak the design.

Thanks in advance

Regards

David

Roy:

Whatever happened to YO? Was that one of your creations which you stopped
selling? Or was it Beezley's?

--
Crazy George
W5VPQ


My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap.
"Roy Lewallen" wrote in message
...
A very good source of starting designs is _Yagi Antenna Design_ by James
Lawson, W2PV, published by the ARRL. It clearly illustrates the various
tradeoffs which can be made in Yagi design, and gives lots of alternatives.
There is no "ideal" design, since there are so many tradeoffs to be made --
gain, front/back ratio, bandwidth, size, which you can't maximize all at
once.

EZNEC doesn't have an optimizer -- if you use EZNEC you have to tweak the
design yourself. People who have used optimizing programs have told me
they've often been able to improve on the "optimized" design by hand
tweaking with EZNEC.

Roy Lewallen, W7EL

David wrote:
Can someone explain to me how a new antenna design is started. Do you
take an initial standard design and then enter it into a modeling program
and optimize it for the required parameters ?

Is there a suitable reference book that would explain this process. I am
thinking about the Cebik antenna modeling book but think this may only
cover how to model and change an existing design,would it cover how to
come up with the initial design in the first place ?

Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm
diameter elements.

Is there a standard formula that would be used to calculate initial
lengths and distances between elements. Then you enter this design into
say EZNEC and use the optimizer to tweak the design.

Thanks in advance

Regards

David

Crazy George wrote:
Roy:

Whatever happened to YO? Was that one of your creations which you stopped
selling? Or was it Beezley's?

That was Brian Beezley's program. The last I heard, you can still buy it
and his other programs, but only by mail. Look up K6STI in one of the
amateur radio databases for his address.

Roy Lewallen, W7EL

There are many parameters to chose in designing an antenna. Beyond the
antenna itself are the costs, tolerable size, available materials and
available tools.
I recently took the ARRL antenna course and purchased Roy's EZNEC+
program. I describe my current level as an "advanced beginner".

I once scaled a 4 (5?) element yagi for an antenna measuring event
from the Arrl Handbook to 1296mhz using a piece of plastic tube for a
boom and #12 wire for elements. The measured gain and the plot looked
pretty much like the book said it would. It fits in a "book-sized"
box.

My current project is "What can I do with a 20 foot radiator?" Working
out the details (the devil is indeed in the details!) sure is a lot
easier with EZNEC than it is with physical modeling.

There are not many antennas that cannot be evolved from a straight
piece of wire.


On Thu, 12 Jan 2006 00:39:01 GMT, David
wrote:

Can someone explain to me how a new antenna design is started. Do you
take an initial standard design and then enter it into a modeling
program and optimize it for the required parameters ?

Is there a suitable reference book that would explain this process. I am
thinking about the Cebik antenna modeling book but think this may only
cover how to model and change an existing design,would it cover how to
come up with the initial design in the first place ?

Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm
diameter elements.

Is there a standard formula that would be used to calculate initial
lengths and distances between elements. Then you enter this design into
say EZNEC and use the optimizer to tweak the design.

Thanks in advance

Regards

David

John Ferrell W8CCW

John Ferrell wrote:
My current project is "What can I do with a 20 foot radiator?" Working
out the details (the devil is indeed in the details!) sure is a lot
easier with EZNEC than it is with physical modeling.

Assuming a 20 ft. vertical with 20 ft. radials, how about
feeding it with an autotuner, like the SGC-230, and using
it for 40m-10m? It will also work at reduced power output
on 75m.
--
73, Cecil, http://www.qsl.net/w5dxp

On Wed, 11 Jan 2006 18:53:06 -0800, Roy Lewallen
wrote:

A very good source of starting designs is _Yagi Antenna Design_ by James
Lawson, W2PV, published by the ARRL. It clearly illustrates the various
tradeoffs which can be made in Yagi design, and gives lots of
alternatives. There is no "ideal" design, since there are so many
tradeoffs to be made -- gain, front/back ratio, bandwidth, size, which
you can't maximize all at once.

EZNEC doesn't have an optimizer -- if you use EZNEC you have to tweak
the design yourself. People who have used optimizing programs have told
me they've often been able to improve on the "optimized" design by hand
tweaking with EZNEC.

Roy Lewallen, W7EL

I second Roy's recommendation and add one. If Yagi antennas are the
interest then in addition to Lawson, you need Leeson; "Physical Design
of Yagi Antennas", by David Leeson, W6QHS.

It is not enough to come up with a super-duper electrical design if
you can't actually assemble it or keep it in the air after it's
assembled.

For example many "optimized" or "fifty-ohm feedpoint" designs are so
mechanically unbalanced that they put a large unbalanced strain on the
rotator if mounted near the boom center. If mounted at a static
balance point they turn into a windcock and damage the rotor from that
stress.

So a well engineered antenna is one that not only performs well from a
gain, FB and SWR standpoint, but is also easy on the tower and rotator
and will last years in the air without degradation.

You miss my motives!
I have a Cushcraft A4 beam that works very well with my Ten Tec
Pegasus transceiver (inboard LDG tuner). In my eyes it is the perfect
rig!

I am not breaking any new ground. I am simply doing the lab exercise
of validating the EZNEC calculations. I may find it worthwhile to drop
to an 8-foot radiator and higher (10-Meters?) for ease of
construction. The principal area of interest is in radiators less than
1/4 wave in length.

At the moment, I am especially interested in the different feed
arrangements. I am starting with the "Gotham" style of a single base
loading coil and minimal radials then I plan on an autotransformer
arrangement. I have a fair amount of room, a lot of scrap metal and
wire is cheap! The principal limitations are time and my level of
intellect...

Staying on track will be a problem, moving the load up the radiator is
already looking appealing!


On Thu, 12 Jan 2006 15:14:32 GMT, Cecil Moore wrote:

John Ferrell wrote:
My current project is "What can I do with a 20 foot radiator?" Working
out the details (the devil is indeed in the details!) sure is a lot
easier with EZNEC than it is with physical modeling.

Assuming a 20 ft. vertical with 20 ft. radials, how about
feeding it with an autotuner, like the SGC-230, and using
it for 40m-10m? It will also work at reduced power output
on 75m.
John Ferrell W8CCW