10 Meter Slim Jim Antenna

OK, I am going to take the plunge and make my own 10M SlimJim out of 450 ohm ladder line. To be hoisted into the tree in the front of the yard. I have all the stuff:

  • 10M of 450 Ohm Ladder Line
  • In-line SO-329 Connector
  • 90 Degree SO-239 adapter so the feedline hangs vertical with less stress on the SO-259 coax connector.
  • Liquid electrical tape to protect against the elements

The instructions are courtesy G0KYA. For your convenience click 10m_slim_jim for instructions.

  • My antenna at 7.48M resonated at 28.2MHz with a SWR of just under 2 when hung. Not so hot.
  • Going for 7.27M to center at 29MHz. Will tune for low SWR after getting the center frequency correct. Fakeout: Got SWR of 1.5 at the same center frequency.
  • Move the tap up to 25cM and remove the short, i.e. original length. This worked well.
    Initial w/1M Coax to Analyzer, I was standing right next to the base of the antenna holding the analyzer.
    Initial Tuning 1M RG-58

With 50 Feet of RG-58
Initial 50ft RG58
Note that I was standing about 10 feet from the base of the antenna. SWR got very bad when I went upstairs, the antenna could not be hoisted up due to a branch, so the bottom was about 1 foot off the ground and when I was sitting in the office I was about 4 feet away halfway up, which severely detuned the antenna.

After hoisting into the tree, in my office at the end of 50 feet of coax.


The antenna itself. Note the plastic icing tub used to keep water out of the connection. The feedpoint is probably about 5 feet down from the peak of the roof, I could not get the antenna any higher into the tree.


Some other shots showing construction detail. I used a paint stick which was painted black to form an end piece to attach a carabiner to hoist the antenna and a middle piece to reinforce the 6cm stub cut out to form the “J”. Tie wraps were used with tightly drilled holes to attach the wood to the antenna.

Top Mount stub stiffener Feedline Detail

National Museum of the United States Air Force

Spent the day at the museum today. It was a blast! We really didn’t get to two of the four buildings, so we have to go back to see the Southeast Asia War Gallery, the Korean War Gallery and the Cold War Gallery. The Early Years, World War II and Building 4 galleries were spectacular. Heading home today after a wonderful Thanksgiving weekend spent with Dave, Samantha and Dan.

Our Museum Photos