On Feb 27, 11:16 am, "JIMMIE" wrote:

no need to be surprised at having an antenna with elements that are
all phased. I doubt if ther is anyone on the news group that doesnt
know that a Yagi Uda antenna doesnt represent some kind of comprimise
to an antenna with all of the elements feed. No one has ever said
otherwise although you have claimed they have.

The problem with having all the elements feed is that it is
impractical to control power distribution and phasing when changing
frequencies.

This is just not true. A SteppIR does it mechanically by changing the
element lengths. A 4 square does it by switching ports around on a
phasing network. One can buy everything you need to build a generic 4
element HF phased array with computer adjustable LC networks for less
than a few thousand dollars. (see, e.g. LDG's AT200PC tuner with an
RS232 interface)

The Yagi Uda overcomes this problem at a slight cost in
gain. Your idea of an antenna with multiple fed resonant elements is a
giant step backwards to a day when high gain steerable antennas were
impractical most of the hams who didnt have the money or the real
estate for huge arrays

hardly backwards. Phased arrays may well save the day in this era of
ever increasing community resistance to traditional Beam on rotator on
tower installations.

Antenna with multiple resonant element all being fed is very common in
RADAR and space communication, you can achive very high gains in this
manner just as you have stated.

You can get low gains too. or just sharp adjustable nulls, which is
probably more useful.

It is also very expensive, has narrow
bandwidth and is a mechanical nightmare.

Expensive compared to what? We're not talking about a electronically
steered phased array radar here with thousands of elements. I'll bet
the hardware cost of a electronically steered phased array for HF
suitable for ham use is comparable to the hardware cost of a big
tower, rotator, and Yagi.. the phased array just isn't available as an
off the shelf product yet.


NASA, AM BCB, commercial
shortwave stations and various other agencies and private companies
sometimes have a need for this type of antenna and they they have the
money to build them, few hams do.

A ham could build an adjustable directional array of verticals,
essentially identical to an AM broadcast directional array, for
several thousand dollars. Yep, that's a bunch o'bux compared to a
Rockmite and a wire over the balcony railing. But it's not a bunch
o'bux in the context of a big station with a legal limit amp, a state
of the art transceiver, etc. If you're willing to homebrew and
scrounge, you can build computer controlled phasing networks with
stepper motors (or servos), roller inductors and variable caps.
Adjusting it is non trivial, but so is learning Morse code, or how to
use NEC or lots of other things in ham radio.. it's just not
particularly common. All the math and design information is laid out
in detail in ON4UN's book, with the implementation left "as an
exercise for the reader".

Jim, W6RMK