The problem of an electrically short antenna is familiar to anyone operating in medium-wave bands. One solution is the counterpoise ground system, which is a series of radial wires that act as a low-resistance ground connection.
Broadcast Engineers use counterpoise systems to improve AM radio station coverage. Coastal Maritime Stations with limited space use them in conjunction with capacitance hats as a tuning method. HF Backpackers even tie a long radial to their whip antenna to improve their own signal as they hike.
When I read an article about applying the concept to handhelds, I was intrigued.
The antenna on a typical handheld is a vertical monopole with the radio chassis serving as a ground plane. This configuration is terribly inefficient because the antenna is a fraction of a wavelength it should be. Your radio may be rated for 5 watts, but you’d be lucky to have a third of that power radiate from the antenna.
By adding a 1/4-wave counterpoise, you, in effect, turn the antenna into an off-center-fed, vertically polarized 1/2-wave dipole. The modification should improve antenna efficiency so more transmitter power radiates from the antenna than it would without a counterpoise.
Theoretically, it should work.
As an experiment, I added a half-wave counterpoise to my Yaesu VX-8DR during a recent Boy Scout camping trip.
The Communication Challenge
Our Scout Camp is a 700-acre facility on flat elevation. The archery range, fishing dam, and swimming beach are exceptions. They drop 30-35 feet below average terrain over short distances; and it is difficult reaching those sites with 5-watt radios, even though they are less than a mile from most camp sites.
First Test Result
My first test was to see if I could reach a local VHF repeater in nearby Morris, Illinois. Under most conditions, I am fully quiet into this repeater with 1 watt.
I talked with my wife back at our home over the repeater, and she confirmed that my signal was good both at 1-watt and 5-watts.
When I added the VHF counterpoise, I couldn’t kerchunck the repeater on full power.
I was very surprised because the VHF counterpoise, at 19-inches, was nearly as long as the stock VX-8DR antenna. It should behave like a center-fed, 1/2-wave dipole and be 60% to 70% efficient.
I checked my connection and tried again.
I move to a simplex frequency to make sure the counterpoise hadn’t shorted the antenna system.
It did work, but I was 20 feet from the receiver on high power.
Second Test Result
Armed with the knowledge that I had a signal, the next test was a short distance check of 175 yards between our campsite and the dining hall.
When I removed the counterpoise and tried again, the operator on the other end thought I was using the counterpoise and transmitting my test.
I reduced power to 1-watt and carried on the conversation without a problem.
We then tried a UHF counterpoise to see if the fault lay in the construction of the VHF counterpoise.
Again, no signal over the short distance.
Thoughts and Opinions
Without any test equipment, I can’t determine the reason for signal loss. Either the antenna was terribly out of tune and had a SWR greater than 3:1, or the counterpoise I built worked as a shunt away from the antenna. I don’t plan to spend any more time chasing this birdie down.
The antenna theory is logical, but didn’t work for me in practice.
I wouldn’t recommend using a counterpoise on an HT. If you want to improve your signal, construct a better antenna such as a Roll-Up J-Pole.