attach twin-lead directly to PL-259, leave other end unterminated adjust frequency for lowest impedance on MFJ-269 (start around 2000/length in inches, work your way up) 63" from end of N connector to tip of twin lead, found low impedance at 37.9 mhz the twin-lead is transmitting the found frequency in exactly 1/4Y its length convert inches to mhz, the math behind it: 63 inches at 1/4y 63 * 4 = 252 inches 252 * (.0254meters/inch) = 6.4 meters 6.4 * (1sec/300meters speed of light) = .0213 sec mhz/sec 1 / (63 * 2.54 / 100 / 300 * 4) = 46.8 mhz freespace 81% VF start with 300meters/sec (speed of light in free space, divided by 1,000,000) 300 x (1inch/.0254meter, about 39.4) = 11811 inches/sec 11811 x (1quarterwave/63inches) = 187.5 quarterwave/sec 187.5 x (1wave/4quarterwaves) = 46.9 waves/sec 46.9 is mhz not hz since we used speed of light / 1,000,000 simplfying, 300 1 1 1 1 .0254 63 4 all you need to remember: 2950 / quarter wave inches = mhz 2950 / 63 = 46.8 (11811 / full wave inches = mhz, or 11811 / mhz = full wave inches) remember "2950" like the Ranger 2950 calculating velocity factor: if 63" of transmission line had low impedence at 37.9 mhz, and freespace would be 46.8 mhz, velocity factor is 37.9/46.8 = 81% (Stan's measurements give him 83%) once you know VF you can calculate wavelength within the transmission line quarter wave = 2950 / mhz * VF quarter wave = 2950 / 52 * 0.81 = 46 inches so a quarter wave stub of 81%vf transmission line for 52 mhz would measure 46 inches Construction: A slim jim requires a piece of twin-lead 3/4 under wavelength long. VF for radio shack's foam dielectric twin lead is 83%. Other twin-lead you would have to measure. A 300ft roll of their twin lead is about $25 and will supply at least half a dozen antenna projects. It fits nicey into 5/8" CPVC from your hardware store. Velocity factor is only in effect in the transmission line, not in a radiator. In other words, the top of the antenna (above the cut) is an a radiator and works at VF=1.00, the length of the stub below it (and the location of the feedpoint) ARE affected by VF. Full length is 47+3+112=162". Remove 3" on one side, at 47-50" from the bottom. Feed at 7" (15%) from the bottom, with shield connecting to side with 3" removed. Short top and bottom ends straight across, do not bend and twist. Bottom stub is 56.75" before being shortened by velocity factor of 83%. Length of bottom between cut and bottom as well as distance from bottom to feed need to be adjusted if using twin-lead with a different velocity factor. 15% measurement for feedpoint may require some experimentation to set SWR. All measurements made optimal for 52mhz. Metal should be kept 5ft below base of antenna. Do not ground any portion of antenna. Direction feedline leads to antenna may affect SWR or radiation pattern. Optimal construction should produce 7 degree radiation angle. (VERY low) Top to bottom, antenna measures 13.5ft. Adding 5ft below to clamp at yields an antenna a bit under 20ft tall. Simplest installation would be to install inside a PVC pipe, and suspend from a tree. Run feedline away at an angle, and bring suspnension rope to the ground and tie down to keep antenna vertical in spite of feedline pull, since radiation angle is critical. Given the large lengths being dealt with, the affect of the jumper across the twin lead at the top and bottom is negligible. An additional 1/4" or so could be removed on both ends if preferred.