Antenna pattern plots: Good intentions vs. good data

Just say no to handcrafted data graphs

In the 21st century should we believe antenna graphical gain data based on hope and hearsay? J-pole antenna gain drawings are a common bad example.

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.

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.

Hawksbill Mtn. APRS Appalachian Trail Test

This is the view as you approach the top of Hawksbill on the only trail.

The Northern Virginia team of Ham Radio operators and companion hikers manned Hawksbill Mountain for the 2011 Appalachian Trail Golden Packet event. Gear included a Kenwood D710 with Green Light Lab GPS, 2m Collinear J-Pole and a 70cm collinear J-Pole.

Hiking, Hams and Hills – Station #6 of the AT Golden Packet

Virginia hikers and hams supported the White Rock Cliffs (Station #6) of the first Annual Golden Packet Event.

Summarized, we were trying to set up APRS relay stations up and down the east coast to cover and service all points along the Appalachian Trail and surrounding areas. Some RF link analysis was performed and is available for viewing at AT_Golden_Packet_Event using the remarkable Radio Mobile program and A LOT of SRTM elevation data.

Of the fourteen stations planned several points were accessible only by foot. The White Rock Cliffs station was no exception.

Read moreHiking, Hams and Hills – Station #6 of the AT Golden Packet

5/8 Wave J-Pole vs. 1/2 Wave J-Pole EZNEC Shootout

Type “J-Pole” into any search engine and you will see dozens if not hundreds of plans to build your very own J-Pole antenna. Many are variations on the tried and true 1/2 wave design with the 1/4 wave stub at the bottom. Be it a plumber’s delight with copper pipe or ladder line heaven using a trimmed up 450 ohm feed line, many folks have successfully created their own J-Pole antenna with a surprising variety of materials.

However, there appears to be some kind of mystical attraction to the 5/8 wave radiator. Several of the J-Pole designs attempt to make the radiator 5/8 wave in length and adjust the phasing stub to make for a good match.

Let’s compare the two approaches using the models available from the late Larry Cebik’s NEC collection. Here are the contenders each using 3/8 inch diameter copper pipe…

Read more5/8 Wave J-Pole vs. 1/2 Wave J-Pole EZNEC Shootout

Collinear 5/8 wave J-Pole vs. Collinear 1/2 wave J-Pole EZNEC Shootout

While planning for a ham radio hike into the mountains to support the Appalachian Trail Golden Packet exercise, I asked my club members for ideas about a good portable 2 meter antenna.

One response included a link to this web page showcasing a collinear J-Pole antenna using two 5/8ths wave antenna elements.

Read moreCollinear 5/8 wave J-Pole vs. Collinear 1/2 wave J-Pole EZNEC Shootout

2 Meter, 5/4 Wave Antenna Revealed

In a previous post we debunked the 2 meter 5/4 wave antenna as actually an end-fed full-wave antenna resulting in a poor radiation pattern hardly optimal for terrestrial use. The fix was to turn it into a collinear with the addition of a 180 degree phased stub between the two half-wave sections.

Thus, the 2 meter 5/4 wave antenna is bunk… or is it?

Read more2 Meter, 5/4 Wave Antenna Revealed

1/2 Wave vs. 5/4 Wave VHF EZNEC Shootout

A friend of mine is preparing for the upcoming Virginia QSO Party in March 2009. Part of the preparations include a focus on some good VHF antennas to support the heavy use of VHF mobile operations in this party. Vertical polarization is key to success. He spoke of a 5/4 Wave Antenna.

Unfortunately, one web site promoting a 5/4 wave antenna solution failed to realize you can’t make an antenna longer without eventually hitting a limit.

Read more1/2 Wave vs. 5/4 Wave VHF EZNEC Shootout

Jpole vs. Coaxial Dipole EZNEC Shootout

In a recent email from the ARRL concerning ARES topics, a writer compares the coaxial vertical dipole antenna with a J-Pole for VHF work. He says…

“With no real models for comparison, it is difficult to compare patterns for each antenna. I would suspect that the J-Pole would not have an omni-directional pattern and would therefore produce a lobe or lobes giving gain in some directions”

Really?

Read moreJpole vs. Coaxial Dipole EZNEC Shootout

1/4 Wave Monopole vs. 1/2 Wave J-Pole EZNEC Shootout

J-pole antennas are an interesting solution to the goal of more gain with a simple antenna. I won’t go into the specifics of what a J-pole is as there are plenty of sites on the Internet with good plans to help you build your own.

However, there seems to be much hype about j-poles that make some folks think they have some kind of magical antenna properties. Indeed many folks report staggering improvements over their previous antennas. Is all the hype warranted?

Read more1/4 Wave Monopole vs. 1/2 Wave J-Pole EZNEC Shootout

Copper J-Pole Antenna on Play Set

When I built a copper plumbing pipe j-pole antenna for 2 meters from plans on the internet, I really did not know quite where to put it. I built it at my previous QTH as more of an exercise to teach my son how to solder with a torch.

Read moreCopper J-Pole Antenna on Play Set