The title of this discussion should be:
World's costliest yagi ARRAY.
The world's BIGGEST yagi has to be the 5-el monster at 7J4AAL [which I
use for my desktop on Windows!].
The link is:
http://www.smeter.net/7j4aal/antennas.php
Don
N8DE
Quoting Jim Lux <jimlux@earthlink.net>:
> Michael Keane K1MK wrote:
>> At 10:31 AM 3/28/2008, Jim Lux wrote:
>>> Nathaniel Lee wrote:
>>> > This is probably cheaper than mechanically rotating a rhombic!
>>> >
>>>
>>> Wasn't it Jansky who had the rotating array on railroad tracks?
>>
>> Yes, it was Karl Jansky (discover of radio noise from the cosmos),
>> although Jansky's array rotated on tires from a Ford Model-T in a wooden
>> track. It was comparatively lightweight consisting mostly of a wood
>> frame that was only about 20 feet tall (although 100 feet across)
>>
>> The antenna itself was an 8-element Bruce array plus reflector for 20.5
>> MHz. At the time (1930), it was the largest steerable antenna in the world.
>>
>> Janksy's colleague at Bell Labs, Edmond Bruce, not only invented the
>> array that is named after him but the rhombic as well.
>>
>> 73,
>> Mike K1MK
>>
>> Michael Keane K1MK
>> k1mk@alum.mit.edu
>>
>
> So the Jansky array isn't going to hack it for top band. Google also
> turned up some SW broadcast curtain arrays with towers on train tracks,
> which are probably a bit larger (39 and 41m bands maybe).
>
> Let's see.. you don't want the track to have too small a radius because
> it's hard to bend the rails. Let's say, a couple hundred meters in
> diameter. That would give you room for 8 bays across for 40m, and 2
> bays for top band. Vertically, you'd need 150 ft or so for 40m, but
> that would be doable. (Since there are road-able construction cranes
> that go that high). A few engineering challenges, but, overall, not out
> of the question.
>
> Mind you, me being a phased array kind of guy (move photons not metal),
> I'd go for 3-4 towers with the dipoles strung in two axes, and then
> electrically rotate it, but I realize that doesn't have the sort of gut
> level satisfaction of just picking the whole giant antenna up and moving it.
>
> Which brings up an interesting idea. What if you mounted two SteppIRs
> at 90 degrees to each other, in a fixed orientation. Could you
> electrically steer the beam in any direction, *with the same
> performance* you could get from a rotator? A big burly rotator,
> bearings, masts, etc, could cost as much or more as the second antenna.
>
> And, can you do the steering with ONLY the element lengths, hooking the
> two feedpoints in parallel. I think so, but I'm not sure.
>
> By the way, the original post (and the subject) is world's biggest Yagi,
> and while this might be the biggest HF yagi array on one tower, I'll bet
> it's not the biggest yagi. There was a monster 20m Yagi that someone
> built about 20-30 years ago, and, of course, when you go to arrays, you
> look at things like W5UN's EME array.
>
> And then, there are a variety of non-rotatable 75/80 and 40m Yagis made
> with wires suspended from cables between towers, as well as all manner
> of broadcast SW log periodics (granted, not a yagi) that are
> substantially larger than this beast.
>
>
> Jim, W6RMK
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