204 lines
10 KiB
Plaintext
204 lines
10 KiB
Plaintext
|
|
|
|
|
|
|
|
|
|
BUILDING THE 2-METER/70 CM COPPER J-POLE ANTENNA
|
|
By Rick Yost N4VQT 19-October-1992
|
|
|
|
MATERIALS REQUIRED
|
|
10 foot section of 1/2" Copper water pipe
|
|
1/2" copper "T" (2)
|
|
1/2" copper elbow (2)
|
|
1/2" copper end caps (3)
|
|
Electrical solder
|
|
RG-8U or RG-8X or equivalent coax about 7' for "pigtails"
|
|
PL-259 connector (2)
|
|
PL-258 coupler (2)
|
|
UG-176 reducer for RG-8X (2) (not required if using RG-8U)
|
|
Electrical tape
|
|
TOOLS REQUIRED
|
|
Butane torch
|
|
Pipe cutter or hack saw
|
|
File
|
|
Pliers
|
|
Plumber's sand paper
|
|
Soldering Iron
|
|
Ohm Meter
|
|
Measuring tape
|
|
|
|
The overall design of this dual band J-Pole is that the top of the antenna
|
|
is for the 70CM band and the bottom is for 2M. Both matching stubs face
|
|
the same direction. Two antenna leads are used (one "Pigtail" for each
|
|
band).
|
|
ASSEMBLY
|
|
1) PREPARATION OF COPPER PIPE:
|
|
Using the pipe cutter or hack saw, cut the 10' copper pipe in the
|
|
following lengths:
|
|
3/4 wave radial = 39 1/2 inches (2 - Meters)
|
|
3/4 wave radial = 19 inches (70 CM)
|
|
1/4 wave radial = 19 1/2 inches (2 - Meters)
|
|
1/4 wave radial = 6 5/8 inches (70 CM)
|
|
J connector = 1 1/2 inches. (2 - Meters)
|
|
J connector = 1 1/2 inches. (70 CM)
|
|
|
|
The remainder of the copper pipe will be used as a mast mount. Sand the
|
|
ends of all pipes to ensure a clean surface for soldering.
|
|
|
|
2) RADIAL ASSEMBLY:
|
|
Using the copper "T" connector fittings, connect the 2M 3/4 wave pipe to
|
|
the mast mount pipe so that both pipes are joined vertically. At the top
|
|
of the 2M 3/4 wave radial, join the 70CM 3/4 wave using the second "T"
|
|
connector. Insure that the remaining open holes in the T's are both
|
|
facing the same direction. Insert the 2 J connector pipe's horizontally
|
|
into the remaining T openings. Using the elbows, connect the 1/4 wave
|
|
pipe's to the J connector pipe's thereby forming the 2 "J" patterns of the
|
|
antenna (see diagram below). Place the end caps on top of the three
|
|
radials. Lay the antenna on a flat concrete surface (like a garage floor
|
|
or sidewalk) so the connections can be heated and soldered without burning
|
|
the supporting structure. This will also ensure that 1/4 wave matching
|
|
stubs will be perfectly horizontal with the 3/4 wave radials once the
|
|
solder cools. Using the torch, heat the copper T fittings and when
|
|
sufficiently hot, apply the electrical solder to the pipe where it joins
|
|
the T. Do not apply heat directly to the pipe, just the connector.
|
|
Repeat this on all connector joints and end caps.
|
|
|
|
|
|
|
|
Page 1
|
|
|
|
|
|
|
|
BUILDING THE 2-METER/70 CM COPPER J-POLE ANTENNA
|
|
By Rick Yost N4VQT 19-October-1992
|
|
|
|
3) PIGTAIL's ASSEMBLY:
|
|
Cut the 7' length of coax into two lengths, 69 1/2 inches and 14 1/2
|
|
inches. The idea here is to have the two ends of the coax hang down and
|
|
end at about the same point after the coax sections are soldered to the
|
|
antenna. The lengths are NOT critical as long as both ends are at least 6
|
|
inches below the 2M J connector. The aforementioned measurements will
|
|
position the ends of the coax about 11 inches below the 2M J after the
|
|
coax sections are soldered to the antenna. The long coax section will be
|
|
used for 70CM and the short coax section will be used for 2M.
|
|
PL-259 CONNECTIONS for 2M and 70CM:
|
|
If using the RG-8X coax, install the reducer on the coax first. If using
|
|
RG-8U or similar, the reducer is not required. Also, slide the outer
|
|
portion of the PL-259 over the coax. Strip the coax end about 1 1/2
|
|
inches and peel back the shield of the coax to the insulating jacket.
|
|
Strip the insulation off the center conductor about 1 inch. Tin the
|
|
center conductor and wrap the shield around the remaining center conductor
|
|
insulation. PLEASE be certain not to short the center conductor to the
|
|
shield. Connect the PL-259 using a twisting motion to the coax ensuring
|
|
that the center conductor does not short to the shield. Apply solder to
|
|
the tip of the PL-259 (coax center conductor) and the 4 holes (coax
|
|
shield) in the body of the PL-259. The PL-258 coupler can then be
|
|
connected to the PL-259. Using an Ohm meter, ensure that no short exists
|
|
between the center pin and the outside of the PL-259 connector.
|
|
ANTENNA End of Pigtail:
|
|
Strip the black insulating jacket of the coax about 3 inches exposing the
|
|
shield of the coax. Peel back the shield of the coax to the insulating
|
|
jacket and twist the shield to form a tightly woven wire. Using a
|
|
soldering iron, tin the twisted shield. This must be done for both
|
|
the 2M and 70CM pigtails.
|
|
|
|
4) COAX CONNECTIONS:
|
|
2-Meters:
|
|
Scribe a mark on the 3/4 wave and the 1/4 wave pipes exactly 2 3/4 inches
|
|
up from the inside portion of the J connector for the 2M section. (see
|
|
diagram)
|
|
70-Centimeters:
|
|
Scribe a mark on the 3/4 wave and the 1/4 wave pipes exactly 1 7/8 inches
|
|
up from the inside portion of the J connector for the 70CM section. (see
|
|
diagram)
|
|
Soldering the connections:
|
|
This procedure is described for the 2M portion of the antenna and must be
|
|
repeated for the 70CM portion. Using the torch, apply heat to the side of
|
|
the radials where you made the scribes. Apply a small bead of solder on
|
|
the scribe points and ensure that the solder is adhering to the pipe.
|
|
After the beads of solder are somewhat cooled, grasp the coax with a pair
|
|
of pliers and while heating the pipe, (again from the bottom) wait till
|
|
the solder bead begins to liquify and apply the tinned shield portion of
|
|
the coax to the 3/4 wave element. (Be sure to connect the shield of the
|
|
coax to the 3/4 radial as close as you can to the insulating jacket. In
|
|
other words, after the connection is cooled, you will be cutting off about
|
|
2 1/2 inches of unused shield). The tinned shield will also start to
|
|
liquify and the solder will join the shield to the radial. Remove the
|
|
heat IMMEDIATELY after you see the solder on the shield liquify with the
|
|
solder on the radial. Allow the shield connection to cool to room
|
|
temperature. Using an Ohm meter, check for any shorts between the center
|
|
conductor and the shield and also check for continuity between the outside
|
|
portion of the PL-259 and the antenna. Next, the center conductor must be
|
|
|
|
|
|
Page 2
|
|
|
|
|
|
|
|
BUILDING THE 2-METER/70 CM COPPER J-POLE ANTENNA
|
|
By Rick Yost N4VQT 19-October-1992
|
|
soldered to the 1/4 wave radial. Again, after the shield side has cooled,
|
|
bend the center conductor over to the 1/4 wave radial and cut the center
|
|
conductor insulation to allow the center conductor to be soldered to the
|
|
antenna. Solder the center conductor using the same method as you did on
|
|
the shield connection. Allow to cool to room temperature. Cut the excess
|
|
shield and center conductor from the antenna. Repeat the above for the
|
|
70CM portion of the antenna. Using electrical tape, afix the coax to the
|
|
mast portion of the antenna just below the "J" on the 2M portion.
|
|
Likewise, using electrical tape, afix the coax for the 70CM portion down
|
|
the 3/4 wave radial for the 2M portion. (see diagram)
|
|
|
|
Your 1/2 wave copper dual band J-Pole is now complete just add whatever
|
|
lengths of coax you need and a 2-meter and 70 centimeter rig and your on
|
|
the air!
|
|
|
|
DIAGRAM (not to scale)
|
|
|
|
End Cap --------------> ---
|
|
| |
|
|
| |
|
|
| |
|
|
| |
|
|
End Cap ----------------> --- | |
|
|
| | | |
|
|
6 5/8" 70CM radial-----> | | | | <-------- 19" 70CM radial
|
|
Center Conductor ----------> |*------- -*| <-------- Shield
|
|
| | | || |
|
|
1 7/8" | | || |
|
|
| | | || |
|
|
----------> | |_ _ _ || |
|
|
Elbow connector ---------> |_ _ _ _ | | <-------- Tee Connector
|
|
|| | <-------- Electrical tape
|
|
Coax --------------------> || |
|
|
|| |
|
|
|| | <-------- Electrical tape
|
|
|| |
|
|
|| |
|
|
|| | <-------- Electrical tape
|
|
End Cap ----------------> --- || |
|
|
| | || |
|
|
19 1/2" 2M radial ------> | | || | <-------- 39 1/2" 2M radial
|
|
| | || | <-------- Electrical tape
|
|
| | || |
|
|
| | || |
|
|
| | || |
|
|
Center Conductor ----------> |*------- -*| <-------- Shield
|
|
| | | ||| |
|
|
2 3/4" | | ||| |
|
|
| | | ||| |
|
|
| | | ||| |
|
|
----------> | |_ _ _||| |
|
|
Elbow connector ---------> |_ _ _ _|| | <-------- Tee Connector
|
|
||| | <-------- Electrical tape
|
|
Coax's -----------------> ||| |
|
|
PL259's ----------------> ||| | <-------- Mast mount
|
|
| | (remaining tubing)
|
|
| |
|
|
| |
|
|
| |
|
|
|
|
Page 3
|
|
|
|
|
|
|