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Dual-Band J-Pole
J-Pole Antennas

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J-Pole Antennas

The Dual-Band Open-Stub J-Pole Antenna
Built out of heavy duty 3/16" angle aluminum, UHF SO-239 connector with 3/8 aluminum elements and all stainless steel hardware.
  • high performance end-fed dipole gain antenna for both UHF and VHF
  • +3dBi Gain over a 1/4 wave ground plane antenna
  • Handles up to 1000W
  • Solid Aluminum and Stainless Steel - weatherproof, will last a lifetime
  • 60" tall, 5.5" wide 1.5"x1.5" angle bracket
  • Low wind load, grounded antenna
  • Flexible mounting options
  • 21.5" Portable Version for backpack or Go-Kit
  • Wide bandwidth, each antenna individually tuned to 146MHz and 446MHz for 2m and 70cm HAM bands
  • Typical below 1.5:1 VSWR on entire band 144-148MHz and 440-450MHz
  • Each one made and tested by hand, with careful attention to detail
  • Dual-band GMRS+MURS (463MHz + 153MHz) are also available
  • Custom single band UHF or VHF antennas available, 130-600MHz
  • Specify mounting holes (diameter and location) if needed

This Open-Stub J-Pole design is similar to many plans and commercially produced units
however I've made some slight modifications on mine that give better performance for UHF.

Dual-Band UHF+VHF
Dual-Band J-Pole
(optional mounting holes shown)
Portable Version: 3-piece VHF Resonator element
     Portable Dual-Band J-Pole
  • Total length ~21.5", assembles without tools in just a few seconds.
  • Fits in a backpack, toolbox, or Go-Bag. Mounts also on camera tripod
  • 10-32 stainless steel set screws join the mast elements
  • elements screw into bracket for portability
Connector and Bracket (optional mounting holes shown)
Bracket Close-up
Pole-top Mount example
Pole Mount
Reflected Power - analyzer image from one actual antenna
Dual-Band J-Pole Frequency Response
Chart shows average reflected power
less than -15db (<2%) at 146MHz and -15 db at 448MHz.
Mobile Truck Bed Mount
Single-Band: 146MHz, 222MHz, 446MHz (and other frequencies) antennas also available
J-Pole Parts

Want to make your own Dual-band J-Pole?

Here's what you'll need:

Materials

  • 3/16" thick 1-1/2" x 1-1/2" aluminum angle bracket 5.5" long
  • 3/8 aluminum rod, 85" total length
  • UHF Stud Mount 3/8-24
  • Teflon Shoulder Washer, 3/8 iD 1/2 OD
  • Star Lock washer, stainless steel
  • 3/8-24 Coupling Nut, stainless steel
  • 3/8-24 Finish Nut, stainless steel
  • 3 3/8-24 Jam Nut, stainless steel
  • Thread cutting oil

Tools

  • Tape measure
  • Band Saw or hack saw
  • File
  • Square
  • Pencil
  • Vise
  • Drill Press
  • Bench Sander/Grinder
  • 1/8" to 1/2" step drill bit
  • Tap - 3/8-24 and wrench
  • Die (Split) 3/8-24 and wrench

Steps

  1. Cut 3/16" 1-1/2x1-1/2 angle bracket to 5-1/2" length with saw.
  2. Sand/grind ends and file until all burrs have been removed.
  3. Mark on top from edge of angle bracket 3 marks at 1/2" and 1-5/8" and 5-1/16"
  4. Cross each of the 3 marks at 5/8" from edge
  5. Using drill press and step bit, drill 1/2" hole for UHF stud mount on first hole 1/2" from the end.
  6. Using drill press and step bit, drill up to and just into the 3/8" diameter step for each of the other marks, for the vertical elements to screw in.
  7. The hole will be 5/16 at the bottom of the bracket and 3/8 on the top, with the step about 1/16" deep inside the hole.
  8. Using 3/8-24 tap wrench, carefully tap the two 3/8 (5/16) holes.
    • The tap should guide itself in, but it must be perfectly vertical with respect to the bracket, in both dimensions. Visual inspection may good enough.
    • Use a small bit of tap oil on the tap to make it less likely to get bound up in the holes.
  9. Using the file, remove any burrs from the holes and bracket.
  10. Using the saw, cut the 3/8" rod to 59" for the VHF Resonator
  11. Using the saw, cut the 3/8" rod to 18-3/4" for the Driven element
  12. Using the saw, cut the 3/8" rod to 6-3/4" for the UHF Resonator
  13. Using the sander/grinder, grind/sand both ends and bevel the top of each rod so it isn't sharp and won't poke someone.
  14. Using the sander/grinder, grind the lower end in a shallow taper, about 3/8" total, up to about 1/16 max. This taper will help the die start to cut the threads without binding.
  15. Using the 3/8-24 die, cut the threads onto the lower end of each of the 3 rods. The number of threads is the number of complete revolutions of the die, count as you go.
    • 25 complete threads on the VHF resonator
    • 20 complete threads on both the UHF resonator and the Driven element
    • I use a "jig" to keep the die straight so that the threads are straight, but even this doesn't always work.
    • After the threads are cut, use a vise to hold the coupling nut.
    • Screw the new threads on the rod into the coupling nut using some cutting oil to make sure the threads are straight and the rod is straight.
    • Adjust the rod a small bit at a time in each direction to straighten it, if it isn't straight. It won't affect the performance any but it might look wonky if the elements aren't straight.
  16. Mount the UHF stud the 1/2" hole on the bottom (inside) of the bracket, use the shoulder washer, star lock washer, and coupling nut on top (in that order).
    • The center conductor of the UHF connector must be electrically isolated from the bracket.
  17. Screw a jam nut onto the Driven element (all the way up until you run out of threads) and screw the element finger tight all the way into the coupling nut on the bracket.
  18. Screw a jam nut onto the UHF Resonator, about 1/2" up the threads, and screw it into the middle threaded hole on the bracket - nearest the driven element.
  19. Screw the Finish nut on to the VHF Resonator, and up the threads about 1" then screw it into the last hole, and screw on the jam nut on the bottom.
  20. Adjust the lengths of the elements using an Antenna Analyzer or SWR/Power meter.
    • First measure for VHF and adjust Driven element and VHF Resonator lengths to get a good match on VHF. Tighten all of the nuts on these elements
    • Adjust the UHF Resonator height to get a good match on UHF, then tighten the jam nut.

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