J. B. Wood wrote:
Hello, everyone. I'm enquiring as to whether anyone has done NEC2/NEC4
modeling on the subject antenna (including a tower mounting) and operating
on the ham bands.

Interesting designs, I hadn't seen them before.
For a hand-held DF sniffer on 2m, might there be
compactness advantages? What would the approximate
dimensions of be of a hexbeam on 2 metres?

Clifford Heath, VK3CLF

Clifford,

Turn radius is about 12.5" for a 2m broadband hex.

It should be possible to get very deep and narrow F/B nulls by
adjusting the Driver/Reflector end spacing at some cost to the VSWR.

Steve G3TXQ

wrote:
Turn radius is about 12.5" for a 2m broadband hex.

Sorry Steve, I see a pair of W shapes, or a W driver and
4-of-6 hexagon reflector. Which measurement is 12.5" - is
this the radius (length) of the hexagon arms (and hence
also of all the peripheral segments)?

It should be possible to get very deep and narrow F/B nulls by
adjusting the Driver/Reflector end spacing at some cost to the VSWR.

If I'm reading you right, the gap between the ends is the
salient factor here. Suggestions on how big a gap to try
first? Something like 3cm?

Sorry for the newbie-ness. Been doing electronics for 30
years, but only now getting into radio and have never tuned
an antenna. Sorta understand EM fields, but don't have any
RF test gear yet, except for my very nice VK3YNG sniffer
(google it). Maybe I should borrow/buy one of the little
fox-or transmitters to tune up an antenna, but it'll be too
late for this weekend's national foxhunt champs in Mt Gambier.

Clifford Heath VK3CLF.

Clifford,

There are two styles of hexbeam: the older design which has a W-shape
Driver and a W-shape Reflector, and which I call the "classic" on my
web site; and my newer broadband design which has a W-shape Driver and
a U-shape Reflector.

I found in my lab notebook a 2m version of the broadband style; its
dimensions a half-Driver 21"; Reflector 40"; end gap 2.5". I think
I assumed wire construction using #14 bare copper. That would give a
hexagon radius of 12.5".

When I model this with EZNEC I see about 3.8dBd Forward Gain and 19dB
F/B with VSWR=1.4. The problem is that the rearward response is very
smooth and "well behaved" so probably not much use for DF.

If I increase the end gap to 5" the Forward Gain and F/B remain about
the same, but the azimuth pattern devlops deep side nulls (38dB) at
plus and minus 130 degrees which may be useful. The VSWR deteriorates
to 1.8:1.

Hopefully that may give you a starting point for experimentation. If I
get a chance I'll try some modelling experiments on the classic design
also.

73,
Steve G3TXQ

wrote:
Hopefully that may give you a starting point for experimentation.

Steve, thanks. Hopefully I'll discuss it over the weekend
with some of our foxhunt folk and perhaps try some experiments
after that. But you're right, the lobe pattern might be simply
inferior.

Clifford Heath, VK3CLF.

wrote:
Clifford,

There are two styles of hexbeam: the older design which has a W-shape
Driver and a W-shape Reflector, and which I call the "classic" on my
web site; and my newer broadband design which has a W-shape Driver and
a U-shape Reflector.

I found in my lab notebook a 2m version of the broadband style; its
dimensions a half-Driver 21"; Reflector 40"; end gap 2.5". I think
I assumed wire construction using #14 bare copper. That would give a
hexagon radius of 12.5".

When I model this with EZNEC I see about 3.8dBd Forward Gain and 19dB
F/B with VSWR=1.4. The problem is that the rearward response is very
smooth and "well behaved" so probably not much use for DF.

If I increase the end gap to 5" the Forward Gain and F/B remain about
the same, but the azimuth pattern devlops deep side nulls (38dB) at
plus and minus 130 degrees which may be useful. The VSWR deteriorates
to 1.8:1.

Hopefully that may give you a starting point for experimentation. If I
get a chance I'll try some modelling experiments on the classic design
also.

73,
Steve G3TXQ

Hello, Steve, and all. Steve, I see you also have an informative
article that is posted online at
www.antennex.com/preview/Dec507/hexbeam.pdf 73s,

On Jun 4, 1:09*pm, "J.B. Wood" wrote:

Hello, Steve, and all. *Steve, I see you also have an informative
article that is posted online atwww.antennex.com/preview/Dec507/hexbeam.pdf


Yes, that article described the process by which I arrived at the
broadband version.

Since then there have been a couple of write-ups in the monthly
Antenna column of RadioCommunication magazine, and RSGB published the
design in their recent book "Building successful HF antennas". You may
also have seen Leo's (K4KIO) constructional article in the March
edition of QST. All that has generated quite a lot of interest in the
antenna.

I try to avoid exagerated claims for the design - at the end of the
day it's a "compressed" Yagi and performs as such. But it does provide
useful directivity over the five bands 20m thru 10m, with a single
feedline, in a size which suits those of us that don't have a lot of
space. It's also pretty easy to construct from readily-available
materials, although a number of folk now supply complete kits,
including K4KIO and more recently DX Engineering.

73,
Steve G3TXQ

wrote:

I try to avoid exagerated claims for the design - at the end of the
day it's a "compressed" Yagi and performs as such. But it does provide
useful directivity over the five bands 20m thru 10m, with a single
feedline, in a size which suits those of us that don't have a lot of
space. It's also pretty easy to construct from readily-available
materials, although a number of folk now supply complete kits,
including K4KIO and more recently DX Engineering.

73,
Steve G3TXQ

Thanks for the reply, Steve. As for exaggerated claims, I'd have to
give the award to the designers of (and explainers of the "theory"
behind) the Crossed-Field Antenna (CFA). (Of course the CFA has been
the subject of numerous antenneX articles but I'm not placing yours in
that group!) 73s,