Slim Jim Cut Planner

Enter your frequency and the wire you're actually using. It returns one continuous length to cut, exactly where every bend and the gap fall along it, and where to tap the feed — measured from one end with a tape.

73 de VA3VMO

Design inputs

Target frequency — where the dip should land

MHz

Conductor velocity factor — the lever that got you last time

Element spacing — the width of your printed frame's two channels

Cut-long margin — extra on the radiator end to trim down to the dip

Show results in

Cut one wire

Total length to cut
(includes cut-long margin) —

Measure from end ①	Do this

Reference dimensions

Sensitivity: the quarter-wave stub is ~3× as touchy as overall length — 1 mm off the stub ≈ 3 mm off the whole antenna. Trim the radiator end, not the stub, when chasing the dip.

Get your wire's real VF — from the assembled antenna

Works even before it's tuned — it doesn't need to be on frequency, just built and connected. Measure the SWR dip at the feedpoint wherever it currently sits, measure the overall length along the wire (end ① to end ②, following the curves, including the gap), and I'll back out the wire's true velocity factor. No test wire, no ground plane, no separate rig — the assembled antenna is the measurement.

Overall length as built — along the wire, end ① to end ②

Where it resonates now — SWR dip, read at the feedpoint

MHz

Enter both values, then Solve.

Trim to frequency — how much to cut, no maths

Built it, cut long, measured the dip? Tell me where it sits now and where you want it — I'll give you the exact snip. Assumes you built to the cut list above.

Resonates now at — the SWR dip, read at the feedpoint

MHz

Want it at

MHz

Enter both frequencies, then check.

Live blueprint

conductor gap & feed dimension width not to scale · gap enlarged for legibility