Ameritron RCS-4
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| Frequency | 1.8-60 MHz |
| TX power | 1500 W (the original manual rates 1500 W continuous; the current storefront copy (on the surviving 4L page) says 2500 W average - version-dependent figures, both official) |
| Modes | n/a |
| relay box | 4x SO-239 antenna ports + 1x SO-239 to control console |
| control console | 1x SO-239 to radio/amplifier ("STATION") + 1x SO-239 to relay box ("RELAY BOX") |
| note | control voltages travel through the coax, NO separate control cable needed |
| power req | 120 VAC 50/60 Hz at 5 watts (control console plugs into wall outlet, NOT 12VDC). RCS-4X variant for 220/240 VAC. |
One coax run instead of four is the entire economic argument, and the RCS-4 adds no control cable to the bill - for remote masts, towers, and buried runs, the over-coax trick pays for the switch in saved copper alone. The relay hardware is honest 1.5 kW continuous duty, and the weatherproof box has decades of rooftop survival behind it.
The over-coax cleverness writes the compatibility rules: DC-grounded antennas, shorted-stub matching, and certain in-line accessories confuse or defeat the control scheme, and four positions is the ceiling. VHF stops at 60 MHz, and post-2024 support is parts-bin and community.
The classic answer to 'I'm not trenching four feedlines': elegant where it's clever, particular where the cleverness collects its fee. Read the DC-compatibility notes before buying, and it serves for decades; ignore them and the mystery hunt begins.
The RCS-4 solved the antenna farm's most expensive problem - the feedline bill - with its era's most elegant trick: the control voltages for its four-position remote relay ride the same coax that carries your RF - 12 volts in both AC and DC flavors, with polarity and AC-versus-DC combinations encoding the four selections for the relay box's diodes to decode. One cable leaves the shack; at the mast end, a weatherproof box full of 10-ampere relays on a G-10 fiberglass board routes it to whichever of four antennas the desk console's switch selects, LEDs confirming the choice, fifty milliseconds after you ask. No control cable, no trench, no conduit - for remote installations the switch paid for itself in unpurchased copper.
The cleverness collects a fee in compatibility homework: because the feedline carries the control voltages, the switch wants DC-isolated antenna feedpoints downstream - a DC-shorted feed (grounded designs, shorted matching stubs, certain in-line accessories) loads or defeats the encoding - and while the manual's stated caution is general, the physics is specific, and reading it is the difference between decades of service and a mystery hunt. Its most practical paragraph: with control power off the box defaults to antenna 4, so 'it would thus be wise to put the most frequently used antenna in position 4.' Power handling reads 1,500 watts continuous in the original manual (the surviving storefront copy says 2,500 average - take your era), which covers HF amplifiers and the 6-meter afterthought alike.
Its catalog sibling the RCS-8V takes the opposite trade - a dedicated control cable in exchange for five positions, higher power, and VHF reach - and the pair mapped the remote-switching decision for a generation: cable-free convenience versus conductor-fed capability. Production ended with MFJ's 2024 shutdown (Ameritron was not in the ITU asset sale), leaving a steady used market and a field-serviceable relay board that rewards owners who can solder.