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My Quad Project I am a firm believer in the phrase,
" Why reinvent the wheel?". When all was said and done,
my SWR readings were 1.3 to 1.7 on the 10-meter band. At one
point during the tuning phase, I had a reading of 1 to 1 at about
29.5 MHz. I tried to stay with an age-old design but also used
commercially available parts. This kept the weight factor manageable
for a 10 or 11-meter size quad. My PVC version sports vertical
polarity plus an easy to change coaxial feed to the driven
element. The thing turned out quite well cosmetically
and I was very pleased with the electrical properties. I was
involved in building a similar antenna in the mid 60's. Back then, many of
us had a CB Radio. The basic design hasn't evolved much
but the construction material has. This antenna weighs just
about 20 pounds, the sixties version was nearly 45 lbs and all
wood.
The Boom is 63 inches from end
to end. I used 60 inches of 1 1/2 inch sch 40 PVC pipe. The
pipe is secured to the end hubs with 1/4 x 2 1/2 inch
stainless machine thread carriage bolts and nuts. By not cementing
these in place, it allowed me to construct each end section one at a
time. It also makes any future repair allot easier. The two 5 way
hubs that support the spreader arms are also PVC. These came from an
on-line greenhouse building supply company.
I used the dimensions from an
on-line quad calculator to provide the exact length wire needed
for the reflector and the driven element. I measured these very
precisely but left about 6 inches of extra wire on each end. The wire has a white plastic
coating. I used a black marker to mark off each quarter length. I
colored 1/2 inches on either side of that mark with a red
marker. This made adjustment simple when I slid the fiberglass rods
out to their proper position.
I secured the wire in place with small nylon pull ties and a
dab of hot glue on either side of the nylon
tips. The reflector wire is cut at the beginning
of the first red mark and at the end of the last. I striped the
coating back 1-inch on each end. I then overlapped and soldered the
two ends together. The Boom mounting plate (shown below) uses two stainless 1 7/8th" exhaust clamps and two 1 1/4" mast clamps. This picture shows a piece of aluminum plate 1/4" X 4" X 12". I drilled and attached the plate to the boom centered and plumbed. The aluminum plate and the stainless clamps came from "That" on-line auction or buy-now web company.
Moving to the business end of the boom, the supporting structures are exactly the same as the reflector end with only one minor change. The beginning and end of the driven element are attached at either of the horizontal spreader arms. At this tip, I expanded the 1/8th hole to a 3/8th hole. I placed a 2 1/2 by 3/8th inch machine thread nylon retaining bolt here as an attachment point for either end of the wire. I needed a thin machine thread nut so I sawed one in half. After tapping the bolt into place, I was left with one half of the nut on either side of the nylon tip. I secured the nut with a small bit of hot glue. I drilled 1/8th inch holes through the nylon bolt on either side of the nuts parallel to the boom to secure the element wires. Now I threaded the wire through the tips. I placed the black mark at the center of the
nylon tip then carefully held the wire in-place and passed the
correct amount of wire through the 1/8 inch hole and secured it in
place with a pull tie and hot glue. I repeated this on the opposite
side of the tip. I did this to make certain each wire was the same
length as the other 2 sections. It only took seconds to do this but
it takes a lot of words to describe the
process. After securing the wires with wire ties and
hot glue, I was left with 2 short ends. I stripped the covering off
each end exposing copper to the black marks. At this point, I slid
the last spreader arm out to take up the slack in the wires and
tightened the stainless hose clamp.
If you look at the next to last picture
above, you will see a small aluminum project box. I stripped out about 6 inches of coax shield
from some spare RG58 cable and divided this in two. I drilled a
small hole next to each grommet as attachment points for small ring
connectors. I secured these with sheet metal screws. I slid a section of shield
down each short feed wire and soldered part of the shield to the
ring connectors. I slid a piece of shrink tubing down each wire. I
soldered each wire to a feed point and slid the shrink tubing over
the joints. I slid the braid up to the beginning of the plastic
coating on one of the element wires and secured it with a pull tie.
See
Feed Point Drawing here! At this point,
I attached my SWR meter and started adjusting the braid exposing
more or less of the unshielded portion of the remaining feed wire
until I achieved the lowest SWR. I used another pull tie and covered
the braids with electrical tape. This completed the antenna.
11 Meter
Quad length chart: 11 Meter CB Center Freq: 27.205Mhz Total Arm Dimension In
Inches: Each Side
(Inches) Finished (Boom length = 62
inches) Reflector: 80
3/8 Reflector: 113 5/8 454
3/8 Driven: 78 3/8 Driven: 110
7/8 443
1/4 One last thing, I had
to buy a short piece of clear 1/2" dia. plastic tubing and cut
it into 2 inch sections. I slid two pieces onto each of the
fiberglass spreaders before inserting them into the 12-inch spreader
supports. Seems the 1/2 inch dia. PVC pipe, isn't 1/2 inch
inside, its 5/8th". Balun - 2:1, High Power, 1.8 to 30 MHz, Cast
Aluminum Gasketed Enclosure - DXE-BAL100-H11-C. I located this item on the
following website.
DX
Engineering.com Greenhouse
Megastore PVC 5 way connector Local hardware stores, auto parts stores, etc
for
hardware |
