Hi Cal,
I use a 5 element 2m quagi for one of my rovers. It works quite well
for its intended purpose. Mine is built to be quick to assemble and
disassemble, and the boom is hinged in the middle to stow in a small
airplane.
I've used a 6 element WA5VJB “cheap yagi” on 2m during the same
contests out of a car, where the antenna can be permanently mounted.
(You can see photos of both of them in action in different
configurations in the same contest here:
http://tinyurl.com/ww7dJunVHF12R ). The 5 ele quagi and 6 ele "cheap
yagi" have similar boom lengths--the Quagi is 7' and the yagi is 6'.
I've set-up both the 5 ele Quagi and 6 ele cheap yagi in my back yard
on separate 20' masts and done A/B comparisons during a weekly 2m SSB
net. I was hoping to learn that one substantially outperformed the
other. It wasn't the case...they performed identically.
Both antennas use wood booms, and I would rate them as equally easy
to build. The LFA array, mentioned by G0BSU, uses a metal boom with
the elements insulated from the booms by plastic insulators, so
construction is a bit more complicated.
Quagi construction hints: Use bare bronze brazing rod for the loops.
Avoid using copper wire. It isn't stiff enough and the resulting loops
look like hell and deform easily. I use 3/32 rod for a lightweight
quagi that isn't subjected to 70 MPH winds. 1/8" rod would work for
beefier loops that must endure highway speeds. (If you insist on using
copper wire, work-harden it by chucking it in a drill, anchor the other
end in a vice and aggressively twist the wire.) The welding rods are
not long enough to form the entire loop. One way to complete the loops
is use high quality electrical butt crimp connectors to form the
corners. Remove the plastic, bend to 90 degrees, insert the welding
rods, use a punch to mechanically crimp and then solder the connector to
the rods. I prefer 3/16th aluminum rod for the directors.
LFA arrays: For the recent UHF contest I built a shortened (8') 432
MHz LFA array for my street rover. I used spruce blocks instead of
plastic insulators. A single machine screw with a washer and a Nylock
nut (all stainless steel) holds the insulator to the boom. The nut is
tightened enough to hold the elements in place at highway speeds, but
the reflectors and directors will rotate (instead of bending) when hit
by tree branches and whatnot. That is an extremely useful feature for a
street rover. I've not done A/B comparisons to the cheap yagi it
replaced. I intend to eventually build 222 MHz and 2 meter LFA arrays
for the street rover, perhaps one by September and the other by January.
In conclusion: All three designs have been successfully used for
roving. The LFA yagi is the newest and sexiest design but, without
additional design work, requires a metal boom, is heavier, and a bit
more complicated to build. But the antenna is expected to perform
better for some useful characteristics. The 5 ele quagi and 6 ele cheap
yagi have similar performance, and are both extremely simple to build.
If vertical mast space is a limitation, the cheap yagi is best. The
quagi's vertical loops make it more susceptible to getting snagged on
trees.
Best,
Darryl
ww7d
On 08/19/2013 06:23 AM, Cal Zethmayr wrote:
Has anyone on this forum built or used a Quagi on 2 meters? Anyone currently
using a Quagi?
Any comments welcome.
Cal Z
W4GMH
Crestview,Florida
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