There are a lot of different yagi designs available, and
some are very easy to build. The method shown on this
page is one of my favorites:
http://oldweb.clarc.org/Articles/uhf.htmNote that these are designed for the lower part of the
2m band, but you can shorten all the element lengths by
about 1% if it doesn't work well enough at the top end
for you. I build them using PVC pipe for the boom, and
the elements slip right out and store inside of it, so
they take up very little space when not in use.
Actually there are several construction methods that allow
the elements to come off the boom. This is the one I use
when I have to take a yagi overseas in my carry-on luggage:
http://home.att.net/~jleggio/projects/rdf/tape_bm.htmI don't bother with the hose clamps - just several wraps
of fiberglass strapping tape to hold the elements to
the PVC fittings. (I do put a sheetmetal screw in each
side of the driven element, though.) I roll or fold up
the elements and secure them with rubber bands then pull
the PVC pieces apart to put it in my suitcase.
Another good option is a quad - I make mine with PVC
fittings and copper wire. The elements pull off of the
boom and stack nicely when I want to carry it in the
trunk of my car. I don't have a description of it online
(though I'll be glad to explain it further), but here
is another fold-up quad option:
http://www.qsl.net/nz0i/projects/quad/quad.html