KØEMT's 80M Field Expedient Dipole Antenna

Summary

This is my 80M "field expedient" antenna. I primarily use this as a NVIS antenna with my FT-817 QRP rig.

Materials:

  • 16 Gauge Speaker Wire
  • Crimp style BNC connector
  • Radio Shack right angle "solderless" connector
  • F-F-F BNC T from Radio Shack
  • 2 16 Gauge Ring Terminals

Construction:

  1. Cut the zip cord a bit long (as usual) ~68 feet
  2. Pull it apart so you have each side of your dipole
  3. Strip and solder one end of each wire
  4. On the crimp style BNC connector
    1. Wrap the soldered end around the shield collar
    2. crimp it and solder it to ensure a good connection
      The center conductor will not be used on this connector!
  5. On the right angle connector
    1. Wrap the soldered end around the center conductor screw
    2. Tighten down the screw
    3. Solder it to ensure a good connection
    4. Make a right hand knot around the shield clamp to give a bit of strain relief
    5. Clamp the shield connector down around the insulated wire
  6. Connect them together with the FFF BNC T
  7. Connect to your rig/analyzer with appropriate coax
  8. Tune/prune to appropriate length
  9. Finish off ends of wire with ring terminals
    1. Strip a bit of insulation off of the wire
    2. Tin the end
    3. Crimp on the connector
    4. Solder the connector

Notes

  • Use "reuseable" zip ties to manage transport/storage of this antenna.
  • Pick up a piece of 10-base-T RG-58A/U "Networking" Coax with Male BNC's at each end while you're in Radio Shack. (Over with the computer stuff.)
  • Obtain two lengths of nylon cord of a size that will easily go through the eye of the ring connector. Used for tying off of trees, poles, etc.
  • The bag I use has two side pockets. One half of the dipole goes in each side.
  • With a small tuner such as the Emtech ZM-2 or LDG Z-11 you will most likely be able to work 80M-70cm with this antenna. (I found I could use the ft-817 on several bands as constructed.)
  • I am not affiliated with Radio Shack or any other retailer.
WA2ZKD suggested the following (edited):
  • The BNC connectors used are OK for on/near resonance and QRP operation. When used at higher power-off-resonance, like with an antenna transmatch, they may arc.
  • For NVIS, an electrically long dipole may not do as well as a dipole cut to frequency. This is because the long dipole may "lobe up" and show directionality.
  • The addition of a simple current balun, such as the W1JR with ferrite on the feed coax, will help and cost little.

Variations

  • On one vehicle I have a home-brew 1/4 wave whip for 6 meters. It is connected to the HF/6 port of an ICOM 706mkII. Disconnect one side of the dipole from the BNC T. Slip it's ring terminal over the mobile whip. Ensure a good mechanical contact. Throw the end with the BNC up in a tree. In some way support it so it's not in contact with ground. Now you can work 80Meters. I checked into the Missouri traffic net with this antenna and received 59 reports.
  • Install Anderson Power-pole connectors at the appropriate places in the wire so that you can make 80-6/2M dipoles. You will have to tape/support the connections in some fashion. If left un-taped/supported spade, bullet and anderson power pole connectors will come apart under tension. (I have emailed Anderson requesting that they manufacture a wrap of sorts that would provide strain relief and lock a single connector together. In the mean time perhaps an overhand knot will do the trick.)
  • Using a small machine bolt, pair of washers, lock washer and nut, connect the halves together at the ring connectors. Plug end with center conductor into rig/tuner for a 160M 1/4 wave. (Do something with the rig's ground connector for this configuration!)

Reports from Builders

  • KCØIFL reports that he built this antenna for 20 Meters. He succesfully used it with his K2 and ATU in an inverted L position from a second floor hotel room.
Picture of 80M Field Expedient Dipole
72/73 de kØemt