This concerns antenna switching and SWR measurements. For convenience the switching and measuring is best done close to the operating position. Perhaps in a console located right next to the radio.
We have built such a console. It contains a multipurpose power supply, a 100 watt linear amplifier, an SWR/Power meter and controls, and switches allowing selection of three antennas on each of two coax feedlines.
POWER SUPPLY
Initially this supply was intended to provide power for a small solid state linear amp and some LED lighting. The amp was for use with the KX3 to boost its 10 watts to a level better suited to drive a larger linear close to full power. The small amp needs 24 volts at up to 3 amps. A 5 amp linear regulator was used to supply the 24 volts.
The transformer in this supply is capable of delivering at least 500 watts. A second 5 amp regulator was installed to provide 14 volts to the KX3 and LED lighting. Additional 1 amp regulators were installed for 12 and 5 volts. The 14 and 12 volt sources were brought out to the back panel through PowerX connectors.
AMPLIFIER
The power amplifier is an EBY design using a pair of IRF540 fets. It covers all bands. A band switch is provided on the front panel. The amp is built into the console along with the power supply. This amp is not protected and must be used cautiously.
SWR/POWER METER
This is an old heathkit meter that can measure up to 2000 watts. Its sensing unit is located remotely to make antenna cabling more convenient.
ANTENNA SWITCHES
There are two switches mounted to the front panel. One for each of two coaxial feed lines. The switches are double pole double throw with a center off position. The switches are connected to remotely located power and coax interface boxes through four wire shielded cable.
These switches route power to antenna relays located on the antenna tower through the coax feed lines. Plus polarity, negative polarity, and power off, select one of three antennas through the relays.
This system is patterned after a Heathkit remote switch which allowed selection of four antennas. The fourth selection was accomplished by feeding AC to the relays where two half wave rectifiers and filter capacitors activate both relays simultaneously. I could not make the AC feature work with the relays I used so I ended up with only three antenna selections.
Both feed line isolators and their power supply are located near the two amplifiers they serve. The amplifiers are located on the floor below the desk. The remote isolators are mounted to the back of the desk.
A patch panel located below the center console allows connection of any number of radios to the amps. When the amps are not powered up or set to standby, the radios are connected directly to the antennas.