Fractal antenna orientation

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 like his collection of weird railroad locomotives.

These are much better, although not perfect.

Horn antennas, being based on aperture,

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.

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).

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

Bigger is better.

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.

Reply to
Jeff Liebermann
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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).

Reply to
Jeff Liebermann

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

And then there's

Reply to
AES

Yep. It's a horn with an added reflector at the top:

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:

An angled horn is used because it covers a wide area.

Reply to
Jeff Liebermann

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.

Reply to
miso

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