Antenna Model · Designer · published-design
J-Pole / Slim Jim
λ = 41.93 m @ 7.150 MHz · Published J-antenna / collinear-J dimensions
FIG.1 · J-POLE / SLIM JIM
Radiator (½λ)
19.916m
Matching stub (¼λ)
9.958m
Overall height
29.874m
Feed tap from bottom
1.394m
Conductor spacing
0.839m
Accuracy note
Starting dimensions — tune the tap and matching/phasing stub(s) for lowest SWR.
Starting dimensions — tune the tap and matching/phasing stub(s) for lowest SWR.
Method published-design Cite Published J-antenna / collinear-J dimensions Feed ~50 Ω at the tap — slide the feed point up/down the stub for lowest SWR.
- J-Pole: a half-wave radiator end-matched by a quarter-wave stub; no radials needed.
- Set velocity factor for your tubing (~0.95). Tap position and spacing are tuned for minimum SWR.