8-Element 432 MHz Quagi
By Paul Bock,
K4MSG of Hamilton, Virginia
Monday, September 13, 2004 8:51 AM
Click here for other articles by Paul posted to the LARG Internet Site
week, I threw together a 8-element Quagi for use in the September
VHF QSO Party. The antenna worked pretty well. There wasn't time to put
it outdoors on the mast so it was mounted in the upstairs hallway adjacent
to the shack, about 18' above the ground and surrounded by house wiring,
ductwork, etc. The antenna has a wood boom and six 1/8" aluminum rod directors. The driven
element & reflector are made from #12 insulated electrical wire removed
from a length of Romex and are held in place by Lucite strips mounted on
the wood boom. I used a Type N chassis mount female connector. The coax
in the photo is Belden 8214 foam-type RG-8/U but I recommend something
having lower loss for any run longer than 25 feet.
20 watts on 432 SSB I was able to work as far away as FM17 - Henry, N4HB,
in Richmond, VA and I heard some other stations that I could not work
due to the low power. Had the antenna been outside on the mast I would
have done much better on 432. This antenna, if carefully built and mounted
in the clear, has been measured at between 12 & 13 dBd - that's dBd, *NOT*
dBi - at various antenna measuring contests. If you have to buy everything
to build it the cost should be less than $20 not counting the coax.
The contest was
fun, picked up 5 new grids on 6 meters; the Par SM-50 Moxon antenna on
6 meters worked very well. Unfortunately, my Mirage 2-meter amp died
the night before the contest and I had to disconnect it and run the 706MkIIG
barefoot; the difference on transmit was only 3 dB - 50w versus 100w.
But, I missed the preamp in the Mirage.
This antenna is
based directly on the designs by Wayne Overbeck, N6NB - formerly K6YNB,
as designed in the early '70s and published in QST in 1977, with a follow-up
article published in 1978 on a 15-element Quagi for 432 MHz. A recent
article by Wayne that incorporates all the dimensions for the original
8-element design, plus the 15-element 432 MHz design, and dimensions
for 10 and 15-element 1296 Quagis, can be found on the Internet Click
Quagi dimensions are given in the above article for 8-element versions
for 144.5, 147, 222, 432, and 446 MHz.
I've been working
with Pete Mazzerelli at Gulf Alpha Antennas on a new design of a 8-element
wide-spaced Yagi for 432 MHz based on Pete's current 440 design. I'll be
the first one to try out this new design and I'm anxious to compare it with
the Quagi and see how an $85, computer-modeled all-aluminum Yagi compares
with the super cheap, wood-and-wire Quagi.