Ham Radio Help Desk

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 http://www.packetradio.net/events/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.
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Type “J-Pole” into any search engine and you will see dozens of not hundreds 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…
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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.
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Hello all,

I wonder if any of you had your display unit for your Kenwood TM-G707 2/440 transceiver go blank and reboot even while the radio operates just fine.

If I move the wire with respect to the control head in a certain position this happens.

Is this just a case of dirty contacts between the little cable adapter and the control head or have any of you seen the wire in the cable actually break?
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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?
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Many makers of J-poles for 2 meters claim they can also be used at 70 cm.

It may not be intuitive at first, but the answer, at least from an antenna pattern standpoint, seems to offer some hope.
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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.
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Early one November morning an amateur radio operator was patiently waiting for morning to break in his tree stand in Rappahannock County, Virginia to get in another chance at a deer. Then tragedy. The tree stand broke sending him down to the ground and, we are not sure how, onto a board with nails leaving him near motionless with six nails in his back.
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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?
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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.
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