Fractal antenna orientation

On Mon, 5 Sep 2011 23:03:23 -0700 (PDT), "(E-Mail Removed)"
<(E-Mail Removed)> wrote:

>Well I never knew they tried acoustic location.

It's still around in different forms. I once worked on an accoustic
direction finder for the blind. There's also the rooftop mounted
gunshot direction finder system (which works on different principles).
I used to play with a dish antenna and microphone, which was great for
listening to the neighbors argue across the road.

>I've read some of Douglass Self's papers. If anything, he tends to be
>an audio foolery debunker. However, I haven't read any of his books.

I like his collection of weird railroad locomotives.

>There is a horn design program floating around the net. Freakin' dos.
>I had to run it in dosbox.

These are much better, although not perfect.
<http://users.skynet.be/chricat/horn/horn-javascript.html>
<http://www.flann.com/imagenav/calculator.xls>
<http://www.qsl.net/n1bwt/chap2.pdf> <-- worth reading.
I have some others that are a bit more exotic if you want. Also some
nonograms out of various antenna design books.

>Horn antennas, being based on aperture,
>probably work better in real life construction than say a yagi.

That's an understatement. Methinks yagi antennas doth suck at
microwave frequencies. Except for the size, horns are probably the
best compromise of gain, bandwidth, and beamwidth.

>It is
>tough to cut and space yagi elements to exacting dimensions. But if
>you play with the spreadsheet to simulate horn gain, you can screw up
>a lot and not change the gain too much. Plus they are very broadband.

Yep. Think of the horn as a transformer between the waveguide input
impedance (same an the probe impedance or about 50 ohms), and the
impedance of free space (about 377 ohms).

>Gain analysis:
>avsport.org/microcomm/software/horngain.xls

Nice, but that spreadsheet only covers the water hole frequencies
(1.4GHz) and is only useful for SETI.

>Here again you are gaining aperture and gain at the same time.

Bigger is better.

>And for more entertainment, the fly swatter antenna:
>http://www.w1ghz.org/antbook/chap8.pdf

Yech. Try it and you'll probably hate it.

The problem with the periscope antenna is that the beamwidth the feed
(dish) antenna has to be small enough to illuminate the reflector, or
most of the RF goes away behind the reflector. It has to be much
narrower than the -3dB beamwidth because that only guarantees that
half your power will hit the reflector. There are also reflection
losses (same as a dish) involved. It might work in the near field, or
with large billboard size reflectors, but not for small antennas.
Incidentally, by order of the FCC, that style of antenna is illegal
for commercial use on licensed microwave frequencies.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

>
> >Gain analysis:
> >avsport.org/microcomm/software/horngain.xls
>
> Nice, but that spreadsheet only covers the water hole frequencies
> (1.4GHz) and is only useful for SETI.
>

> --
> Jeff Liebermann * * je...@cruzio.com
> 150 Felker St #D * *http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann * * AE6KS * *831-336-2558


There are just so many things engineered where the tolerances totally
wipe out the complexity.

The spreadsheet frequency range is a function of the waveguide
dimension, so as you scale the waveguide dimension downward, the
frequency range goes up. The dimensions are based on slant length,
while the horn design software is based on length of the horn along
the axis. Easily compensated with a bit of trig.

Most of the time you just see feed horns for dishes, but I've seen X
band horns used at FAA sites. I think for a link between sites. Also
police radar uses horns. Probably aircraft radar too, but I've never
seen the gear.

Put this in the "Do I make you horny" category:
http://www.q-par.com/products/horn-a...tennas/files/1
I suspect they don't sell a lot of horns, but the mark-up makes up for
the low volume.

On Tue, 6 Sep 2011 21:36:00 -0700 (PDT), "(E-Mail Removed)"
<(E-Mail Removed)> wrote:

>Probably aircraft radar too, but I've never
>seen the gear.

Nope. Up to about 1975, it was a movable dish in the nose.
Afterwards, it's mostly electrically steerable phased arrays (some of
which can be tilted downward for terrain following).
<http://militaryforces.ru/firearms-1-11.html>


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article
<a2e99e81-4eae-4951-a644-(E-Mail Removed)>,
"(E-Mail Removed)" <(E-Mail Removed)> wrote:

>
> Most of the time you just see feed horns for dishes, but I've seen X
> band horns used at FAA sites. I think for a link between sites. Also
> police radar uses horns. Probably aircraft radar too, but I've never
> seen the gear.
>

Is the "sugar scoop antenna" considered to be a horn? -- because there
certainly once were tons of those around.

A great starting point for telco history is

<http://long-lines.net/index.html>

And then there's

<http://long-lines.net/places-routes/1st_transcon_mw/BTA52/FC.html>

On Wed, 07 Sep 2011 09:22:04 -0700, AES <(E-Mail Removed)> wrote:

>Is the "sugar scoop antenna" considered to be a horn? -- because there
>certainly once were tons of those around.

Yep. It's a horn with an added reflector at the top:
<http://long-lines.net/tech-equip/radio/BSP402421100/p03.html>
They would work from 4-12GHz (with different waveguides attached).
43dBi gain at 6GHz with about 1 degree beamwidth. Zero side lobes,
which was necessary to prevent co-channel interference. I worked on a
few of those in my checkered past. Aiming them was difficult. Dealing
with temperature drift was tricky. Dealing with the moisture
condensation problem was worse.

Many years ago, I had to deal with a 2.4GHz interference problem,
which turned out to be a plastic injection molding machine pre-heater.
It used a horn antenna feed by a microwave oven magnetron to evaporate
out any water in the feedstock before molding. They're still around,
but were moved to a different frequency a few years ago.

Also, there are moisture meters that use horns:
<http://www.kdctech.com/index.php?p=2_1>
An angled horn is used because it covers a wide area.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sep 7, 9:45*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Wed, 07 Sep 2011 09:22:04 -0700, AES <sieg...@stanford.edu> wrote:
> >Is the "sugar scoop antenna" considered to be a horn? -- because there
> >certainly once were tons of those around.
>
> Yep. *It's a horn with an added reflector at the top:
> <http://long-lines.net/tech-equip/radio/BSP402421100/p03.html>


I've seen lots of "sugar scoop" antennas in the boonies, but not
powered. I've been told the liability of keeping any antenna site
"legal" (as in strobe lights) far outweighs the cost of dismantlement
of the antenna, but it seems these sugar scoops don't follow that
rule. Now to be fair, many of these sites don't have strobes. The
telcos seem to favor serviceability of their sites over say being on
the highest peak. [Note how the telcos like to use microflects.] But
a few I've found strobes, but otherwise in use.

Come to think of it, I recall seeing those sugar scoops on a building.
Maybe in Stockton.

There is an antenna site in Hayward off of Santos Rd. that was an old
fly swatter site. Roughly N 37.65950 W 121.93320 Obviously re-purposed
into a comm site.