I like vertical HF antennas for a variety of reasons: they are easy to set up, they often take up little space, and they can be quite efficient. But like all antenna systems, tradeoffs are involved. An efficient antenna may require more space or take time to set up, while a very compact vertical would certainly lack in efficiency. As portable operators we often need to weigh convenience vs efficiency in our antenna decisions.
One way we can reclaim some of that efficiency in our compact antennas is to move the loading coil from the bottom of the antenna to the center. With coil loaded verticals, the point of highest current will be at the inductance point, that is, the coil. With the coil at the bottom of the antenna, that current is concentrated at the base. but moving the coil upwards moves the high current point to the center of the antenna for better RF takeoff and higher radiation resistance. This can improve efficiency by 1-3dB versus a bottom loaded antenna.
This week’s video, titled Center Loaded Vertical Antennas? The results will surprise you!, delves into center loading a vertical antenna and how you can modify your Chameleon version 1 PRV coil to allow for efficient center loading. https://youtu.be/90SkGWgOsfM
Links and Resources:
How to Convert Chameleon PRV 1.0 to PRV 2.0 https://youtu.be/nXqR2if2LlA?si=k1vA4rTKWaLJ76r_
Courtesy of HOAHamradio
Chameleon PRV 2 Kit: https://chameleonantenna.com/pkywca
Chameleon Faraday Strip Radials: https://chameleonantenna.com/cg0QIe
Chameleon CHA Blank Adapter: https://chameleonantenna.com/hhrbnv
CHA Extender 12: https://chameleonantenna.com/yysfto
Koss SB40 Communications Headset: https://amzn.to/4aITokJ
Use the Koss Headset with your FT-891: https://youtu.be/_j4E6mbrK8o
RigExpert Stick 230 Antenna Analyzer: https://dxengineering.pxf.io/rEQxKD
Building the Chameleon PRV Jumper
Chameleon recently introduced their PRV v2 system. the PRV, or Portable Resonant Vertical, antenna consists of a loading coil, the MCC Coil, 24 inch rod for elevating it, 58 inch whip, the Blank Adapter feed point, and ground radials. Thekey difference between the PRV version 1 and version 2 is in the coil. The version one coil has an integrated UHF connector as feedpoint and the version 2 coil no longer has this feedpoint, relying on the Blank Adapter to provide it. This addresses one of the key issues I had with the MCC in that with the integrated feedpoint, center loading the coil wasn’t very effective.
But for all of you PRV version 1 owners, you are not out of luck and you can easily modify your coil for center loading. There are a variety of methods that you can do this. All that you need to do is to short out the UHF connection on the coil and one of the easiest and cheapest ways is to build a short jumper that connects the center pin of the UHF connector to the ground side of the coil. This allows you to then elevate the coil and use a Blank Adapter at its base for the feed point.
I made a video of the process. This is bonus content for Patrons, but I’ll open it to all newsletter subscribers. Thank you for supporting my work: https://youtu.be/NOVd21WO_5I
To build the jumper, you will need four items: 4mm male banana plug, 3/8 inch ring terminal, 4 inches of 14-16 gauge wire (I used two conductor zipline I had on hand), and a bit of heat shrink tubing.
To construct the jumper, strip the ends of the wire. Next solder or crimp the ring terminal and the banana plug to each end. I prefer soldering for this job as it gives me a stronger connection and I am not worried about high DC electrical currents traveling through the wire. Finish your handiwork with the heat shrink tubing.
Finishing Up
I will be going on hiatus for the first two weeks in May. I have found that viewership drops during Hamvention so I will take a short break as I prepare and travel to the world’s largest amateur radio gathering.
The great news is that you will find me at Hamvention once again. I will be strolling the grounds and touring the buildings Friday and Saturday May 15-16. On Sunday May 17 will be giving a presentation on POTA or Parks on the Air in Building 1 starting at 9:15am. Please check the Hamvention schedule for information and any last minute changes. Please feel free to stop me and say hi.
I’ll publish another newsletter for my Patrons next week and maybe some unscheduled video content.
I hope to get you in the log soon
Michael
KB9VBR
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