Of fields and feedpoints

Understanding how feed position along the half-wave dipole antenna affects the electric and magnetic fields around it.

Slim Jim vs. Traditional J-pole Antenna

Measured gain of SlimJIM and J-Pole

Real measurements of a Slim Jim antenna and traditional j-pole antenna reveal the truth about their respective gain and pattern.

Have your J-Pole and ground it too

1.06 GHz Test J-Pole Antenna

Tame the predictable mast currents found in any j-pole antenna grounding conductive mast using a simple stub. Shown is empirical evidence why this is a problem and a very simple solution all future grounded j-pole antennas should incorporate.

Build this Vertical Portable HF Antenna

This antenna fits into a baseball bag except for the tripod.

The Asymmetrical Hatted Vertical Dipole (AHVD) prototype is an easy to build, portable alternative to other freestanding vertical HF antennas such as the Buddipole.

Asy Hat Vertical Dipole

Three views showing a how a planed vertical need not always be the classic 1/4 wave monopole.

We re-introduce the theory and origins of Cebik’s (W4RNL) Asymmetrical Hatted Vertical Dipole (AHVD) antenna with the hope to facilitate a vertical polarization portable 20-10m aerial for portable operations.

40m Mastless NVIS Antenna

Folded 40m NVIS Dipole Concept

Yet another 40m Cloud Burner design featuring a folded dipole driven element plus one reflector wire to facilitate 40m NVIS contacts without need of a tall mast. The design uses electric fence posts for support and needs no balun.

Superbowl HDTV Antenna

Build the venerable Hoverman TV antenna and watch digital broadcast high definition HDTV television this weekend. This version of a HDTV antenna uses amateur radio antenna building techniques to make a lightweight structure.

Copper 6m Coplanar LFA Yagi-Uda

Azimuth Plots of LFA Yagi-Uda with and without feedline

The Coplanar Loop Fed Array (LFA) Yagi-Uda design from G0KSC provides an excellent design foundation for an all copper version of a 3 element 6m balunless beam with superior front to back performance. Shown are comparisons between model simulations and prototype measurements.

Coplanar Loop Fed Array LFA Yagi-Uda Antenna

Current Magitudes of Yagi-Uda Elements with Low-Z wire on Feedpoint

The clever application of the folded dipole loop, computer science iteration techniques and NEC simulation to Yagi-Uda design results in a panoply of practical planar Loop Fed Array, LFA Yagi antenna recipes.

Improving the Super-J

Full view of various Collinear J-Poles

The traditional collinear J-Pole, aka Super-J, improves the basic J-Pole. Are further improvements possible? By replacing the phasing stub with a simple coil, the answer is yes. The result is the Collinear J-Pole.

EFHW LNR Precision EF-10/20/40MKII Examination

Schematic of LNR Precision 10/20/40 Portable Antenna Matchbox

The background and details of the LNR (Par Electronics) EF-10/20/40 end fed half-wave multi-band portable HF antenna. Come see what’s inside the mysterious “black box.”

Antenna Measurements on Taurus 2m Whip

Return Loss and SWR measurements of a permanent 2m whip installation mid-roof of a Ford Taurus. The effect of doors is shown.

Simulations of Classic & Broadband Hexbeam – The Movie

Many folks have successfully modeled all versions of the Hex Beam. Most of the simulation attempts use NEC programs.

Despite being a popular and productive way of simulating amateur radio antennas, another method of electromagnetic simulation makes use of the Finite-Difference Time Domain (FDTD) method.

Without going into too many details, the method divides up the simulation space into little cubes of volume. Then the next magnetic field values are derived from the current electric fields. Then the next electric field values are derived from the current magnetic fields. Repeat.

FDTD makes use of Maxwell’s equations to calculate the above fields. Being a Time Domain method, what follows shows a movie like display of what is happening in the antennas in super slow motion.

Read moreSimulations of Classic & Broadband Hexbeam – The Movie