Portable 2 Meter Slim Jim antenna using 300 Ohm Twinlead

300Ohm slim jim antenna diagram plan

Due to popular searches, I’ve included a diagram to make a flexible slim jim antenna. This antenna is useful to increase the range of your portable radio or as a simple QRP mobile antenna for emergency situation.

Basic Slim Jim conceptual plan

In order to proceed with this project you need

  • about 165 cm (64 inch) 300 Ohm twinlead cable
  • RG-58 coax cable (RG-8, RG-213 might be too big for soldering), any length but keep it shorter than 7 meters for portable radio
  • Soldering iron
  • Wire cutter
  • Connector to your Rig (usually BNC type or UHF Male)
  • insulating tape

This is an ideal antenna for first timers to build. It is powerful yet simple to construct, once you get the hang of it you would certainly have no problem to construct other variants of Slim Jim antenna using different material.

This exercise would also prepare you in the world of Amateur Radio where real hams homebrew their own antennas.

Important Notes

  • Make sure you solder the center conductor to the longest part of the antenna, and the outer conductor (braid) at the shorter side of the antenna
  • If you use this on mobile rig, keep transmission power lower than 50watt to avoid the antenna from being burned away.
  • Make sure the antenna is held straight for best transmission and reception. Best way to make sure of that is to hang the antenna at a higher place or strap it to PVC pipe or other non-conductive pole

Advantages of 300ohm Twinlead Slim Jim Antenna

  1. Easy to construct
  2. Has radiation angle almost parallel to the ground which makes your transmission goes farther than 5/8 or ground plane antennas
  3. Wideband
  4. Portable; Easy to carry, store and deployed
  5. Can be use during emergency situation
  6. Light and flexible

Completed Antenna
Here is a screenshot of my own completed slim jim antenna which I use with my Icom V8 portable radio.

Completed slim jim 300ohm coax

Upon connecting this antenna to your portable radio, you can feel its differences when compared to using the stock rubber duck or telescoping antenna.

3 Replies to “Portable 2 Meter Slim Jim antenna using 300 Ohm Twinlead”

  1. WILL THIS DO BOTH 2M/440. DUALBAND ANT DEAL. AND CAN IT BE CUT FOR 220 OR 6M. IF SO CAN YOU EMAIL FORUMALA HOW TO FIND THE 3 SIDE AND WHAT HAVE YOU.. KC2JLI NOODLES

  2. Just a comment on the Slim Jim antenna. I built one, tweaked it a bit, hung it from a heat vent in my basement. I connected it to an Icom 91A hand held radio and keyed up on a repeater 92km away. I just wondered if I could get the repeater to see it (remember I was in the basement). Not only did I pull up the repeater but when I asked for a radio check a guy heard me and came back. He said I was a bit noisy. I told him he shouldn’t even be able to hear me. Since then I have made several Slim Jims for others and they are all very pleased with the outcome. I do find them a bit difficult to get tweaked for best performance.

  3. it’works greats,,i build with little.modif on frek i used,,get low swr without calibration anymore,,,,

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