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

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.