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First
get a stove pipe crimping tool, and a stack of big coffee cans.cut the rim off
one end and use the crimpier to prep the edge cut the bottom out of the next can
and rim as above. stick the crimped edge into the bottom of the next can, check
for fit. do this till you have a stack taller than 54".
Make
four of them. wire wheel the joint to prep it for soldering. Assemble the
stack of cans, use three pop rivets around each seam to hold it till soldered.
Then get your propane torch and plumbing solder, sweat the joints. Oh yes, in
the third can from the bottom, mount a disk of plexi-glass with a 9/16th hole in
the middle. This will steady the tuning rod later.
To
make the top of the can use 3/8ths or 1/4 inch aluminum plate. Fit it flush with
the top of the can. drill and tap or use self taping 8-32 screws to hold the top
around the top.
Now
that you have this complete let's get some plumbing done. Get 2 each 8ft
sections of 1/2 and 3/4 copper pipe. 4 1/2 copper pipe caps 4 4ft sections of
5/16ths all thread rod with a bag of nuts to fit., 4 3/4 pipe to 3/4 treaded
copper fitting. four 3/4 threaded pipe caps.
By now
you should be getting a picture of this. cut the pipe in half so you have 4ft
sections. take one end of the 3/4 pipe and cut small long triangles around the
end. you with squeeze this to make it like fingers down to the 1/2 size pipe to
slide through. take a 1/2 pipe cap and drill it to let the all thread through.
take two nuts and secure the all thread to the cap. solder this to the end of
the 1/2 pipe. now solder the threaded fitting to the top of the 3/4 pipe that
you made the fingers on the opposite end. Feed the 1/2 pipe with all thread into
the top of the 3/4 pipe. gently push it through the fingers you made. Test this
for good even firm contact. I used so no ox here just before I did the finial
tune. Take your top plate and drill a hole to accept the threaded top of
the pipe. Drill and tap the 3/4 pipe cape in the center top to take the all
thread. put this on and secure to the top using spacers as needed to secure the
top to the pipe securely. Get some nice knobs at a swap meet and you now have a
basic cavity.
There
are many ways to make the pickups. I made my cans pass/notch and used a so239
panel mount tuning caps out of the finals of a RCA car phone. and the loops were
made from left over 1/2 pipe. I flattened it and sanded the sides to separate it
into two flat peaces. We made the loops 2 3/4 inches long or 5 and 3/4 memory
fades. try it and see what works it is cheep to try. We had to tack some silver
mica caps across the tuning cap to get the notch where we needed
it.
I have
a set of these on the 52.6 -500 repeater in Bakersfield California. it is a 100
watt micor base running at 75 watts with a pre-amp. It has been in service for
about 16 years.
This
is not meant to be complete instructions to build a duplexer. It is just meant
to get you a usable platform to experiment with. with good construction skills
and test equipment it is very easy to make 6 meter duplexers. You can take this
basic setup and replace components and materials based on your skills and
availability.
Lowband is a fun world to play in. Don't let folks tell you you can't do
it or it wont work. IT will, it does and you can.
Kevin King SCSA BSCIS
ARS KC6OVD
GMRS KAG0378
EIEIO 2722
Acworth Georgia
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