Construction Plans for the Model J146/440 ...


Dual Band (2 Meter/70 cm) Solid Aluminum J-Pole

Parts Needed
  • Radio Shack # 21-961 3/8"-24/SO239 Mount (Mobile CB Antenna)
  • Radio Shack # 15-826 TV Mast U-Bolt Clamp Assembly
  • About 85 inches of 3/8" diameter Solid Aluminum Rod.
  • 5 1/2 inch piece of strut angle Aluminum 1 1/2" X 1 1/2" X 3/16"
  • 4 Stainless Jam Nuts 3/8-24 thread (or 3/8-16)

    Tools Needed
  • Drill Press with drill Bits up to 1/2".
  • Tap & Die for 3/8-24 thread.
  • Sander or file to de-burr the cut edges.
  • 9/16 wrenches & a 3/4 wrench.
  • Vice-grips
  • Saw

    Procedure

    Make sure the piece of angle Aluminum is exactly 5 1/2 inches long. Drill two 1/4" holes on one side, centered to fit the U-Bolt for mounting. On the other surface of the angle, measure in 1/2", 1 7/8" and 5" in from left side and drill 1/4" pilot holes. Enlarge the first of the pilot holes to 1/2" for the antenna mount. Enlarge the second and third of the pilot holes to 11/32" then tap the holes with a 3/8-24 tap or 3/8-16. Finish as required.

    Cut a piece of the 3/8" Aluminum rod to about 20". Attach a vice-grip to one end. Using a 3/8-24 die cut in about 8 threads in the other end. Screw on the Coupling Nut that came with the SO239 Mount. Tighten as much as you can. Measure the rod & coupling nut & cut to exactly 19 1/4". Cut a piece of the 3/8" Aluminum rod to about 60". Attach a vice-grip to one end. Using a 3/8-24 die cut in about 14 threads in the other end. If you don’t have jam nuts, cut enough threads for 2 nuts & the thickness of the angle bracket. Screw on one of the jam nuts & tighten as much as you can. Measure from the bottom of the nut and cut the rod to exactly 57 1/2". Remember the nut must be included in the measurement. Repeat for the 6 1/4" long 440 element. Put a small amount of grease on the threads. Screw the element into the threaded hole and tighten. Screw on the other nut and tighten it. Attach the 19 1/4" element in the 1/2" hole using the rest of the SO239 Mount.

    Testing

    Mount & test your new antenna. SWR should be < 1.2-1 at 146 MHz and <1.4-1 at 144 &148 MHz. SWR should be < 1.2-1 from 440 - 450 MHz.

    Redundant Test

    Remove the 57 1/2" element, there should be no change of 440 performance. SWR on two meters will be high. Reinstall, then remove the 6 1/4" element. No change of the two meter performance should occur. SWR on 440 will not change much but the performance will.

    Alternative Method

    If all this sounds like too much work or your just not a builder, this antenna can be bought for a very reasonable price from Allen at Arrow Antenna

    73 Allen Lowe NØIMW Arrow146@aol.com
    Arrow Antenna
    1803 S. Greeley Hwy. # B
    Cheyenne, WY 82007
    Voice (307) 638-2369
    Fax (307) 638-3521