Tom Ring wrote:

Microwave operators regularly use long quads (loop yagis) with 20,
30 and even more elements. Range measurements *prove* that they work,
about the same as conventional yagis of the same boom length, but the
loop elements do have some constructional advantages for the low
microwave bands.
As with any yagi-type antenna, you need to add significant numbers
of extra elements and boom length in order to see a significant
increase in gain. If you do it right, the gain will come.

I think one other factor not factored in (sorry, I just had to do that,
it's friday), is that no one has written a good optimizer for loop/quad
yagis.

I wonder if one could craft a converter that makes equivalent loops out
of regular dipole elements, then you could convert optimized yagis to
loops yagis.

The practical advantages of loop yagis lie in their element
construction, which is a circle rolled from flat strip. Unfortunately,
that is a very difficult shape to model with any software I'm aware of.

That assumes a lot, of course, like spacing between the 2 types works
the same.

Which it doesn't, because parallel-spaced loops are very obviously
different from parallel-spaced rods, and are going to interact in a
different way. The general rules for building yagis are the same -
progressively shorter loop lengths along the boom; progressively
increase the spacing until you reach a certain limit, and then keep it
constant - but the details are definitely going to be different. And
it's those small details that make the difference between a good,
average or poor yagi.

Probably won't work at all, but if it's possible to do it, I bet I have
the way. Same one I gave to Brian to do scaling in YO.

It would certainly be very difficult, but I doubt if it will ever be
done. Existing loop yagi designs are already quite close to the
theoretical optimum for the boom-length, so the limited rewards wouldn't
justify the effort.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek