Using Commercial Manual Antenna Tuners
Since the advent of the microprocessor controlled automatic antenna tuners, the preset tuners used, particularly in the marine SSB market, have started to show up as surplus and can sometimes easily be picked up for a very small fee or even for free. This can be a boon for the amateur operator as these manually tuned couplers can be set up on particular frequencies and then switched from inside the house. The marine housings are usually weather proof and can be mounted at the base of a vertical or inverted L type antenna. So if you are fortunate enough to live where you can get one of these, try to get the instructions and a schematic to aid you in setting up the coupler.
On the left is a photo (Photo 1) of a well-used SGC Q-match preset tuner. It has eleven preset positions and covers from approximately 1.6 to 24 MHz. The case is of high impact ABS type plastic and has been yellowed by the exposure to sunlight in a marine environment.
This photo (Photo 2) shows the top of the coupler and the antenna feed through insulator is visible.
Here is the bottom of the coupler, SO-239 RF connector and the feed through bushing for the control cable. The ground terminal is also visible as is the lower end of the mount for the coupler.
This is the bottom of the coupler and displays the mounting bracket and mounting holes (and some rust).
As far as making these tuners useable, most of the time you can just build a control box adding the control cable, voltage, and you are ready to go. In the case of the SGC shown here, it had been struck by lightning. It has been repaired, but there are cracks visible at the corners of the case. These cracks will have to be repaired by filling them with silastic before the coupler can be placed back outside in the elements. Other than that, all required is a switch box that can switch eleven channels in this case, and a 12vdc @ 4A (intermittent) power supply to power this coupler. The coupler was designed to be switched by the matching SGC transmitter, so construction of a control box is required. This is why a diagram is important. This particular coupler has an off seeking selector. In other words, the Ledex when energized steps until it finds the section of the switch that shuts it off. So an eleven position rotary switch is required. Or, eleven momentary contact push button switch will be needed and the desired switch held down until the Ledex finds the correct position and shuts off.
To be able to tune up the antenna using one of these couplers, it will depend on what type of coupler is used and the way it is wired. If you can get the instructions or some advice on how to do it, it will be so much easier. But, as in the case of so many outdated pieces of equipment, manuals may be hard to come by. However, it will be worth it to have one of these couplers when the weather is nasty and you want to change bands
Originally posted on the AntennaX Online Magazine by Richard Morrow, K5CNF
Last Updated : 29th April 2024