Antenna Switching Systems: Relay Boxes, Remote Switches, and Stacking

Once you have more than one antenna, you need a way to switch between them. And once you're serious about a multi-antenna station — different beams for different bands, receive antennas, stacked arrays — the switching system becomes critical infrastructure that affects every aspect of your operating.

Street prices in this article were checked in July 2026 and move around; verify with a dealer such as HRO, DX Engineering, or GigaParts before you buy.

Manual Coax Switches (Indoor)

The simplest solution: a rotary switch box sitting on your desk.

Common models:

• MFJ-1704/1706: 4 or 6 position, handles 1500W, about $80-120
• Alpha Delta 4B/4N: 4 positions, N connectors, 1500W rated, $100-140
• Daiwa CS-201/401: 2 or 4 positions, well-built, $60-100
• Array Solutions Rat Race: Premium build quality, $200+

Specs to check:

• Isolation between ports: How much signal leaks from the selected antenna to unused ports. 60+ dB is good. Poor isolation means strong signals from one antenna can feed back into another.
• Insertion loss: Should be under 0.1 dB. A good switch is transparent.
• Power handling: 1500W PEP is standard for HF. Ensure it handles your power level at your frequency. Some switches derate at VHF/UHF.
• Connector type: SO-239 is common but N-type is better above 100 MHz.

Pros: Simple, no power needed, reliable, instant switching. Cons: All coax runs to the operating position (more cable, more loss), only usable from the shack.

Remote Antenna Switches (Outdoor/Tower-Mounted)

When you have a tower with multiple antennas, running separate coax for each antenna is expensive and creates a cable management nightmare. A remote switch at the tower base lets you run one feedline to the shack and select antennas at the remote end.

How they work: A weatherproof box at the antenna location contains relays controlled by DC voltage or a separate control cable from the shack. You select the antenna from inside, and relays connect the single feedline to the chosen antenna.

Popular models:

• DX Engineering RR8B-HP: 8 positions, handles legal limit, weatherproof. The standard for serious stations. ~$600.
• Array Solutions PowerMaster/StackMatch systems: Integrated switching with power monitoring.
• Ameritron RCS-4/RCS-8: Budget remote switches, 4 or 8 positions, $200-400.
• Green Heron RT-21 (with relay board): Integrates with their rotator controller.
• Homebrew: Many hams build remote switches from DPDT relays in weatherproof enclosures. Totally viable for $50-100 in parts.

Control methods:

• DC voltage on coax: Some switches use DC voltage on the coax center conductor to select positions. No separate control cable needed. Simple but limited positions.
• Separate control cable: Multi-conductor cable carries selection signals. More reliable, more positions possible.
• Ethernet/WiFi: Modern switches with network control. Configure from any computer on the network.

Installation tips:

• Mount at the base of the tower, protected from direct rain
• Use N-type connectors for all connections (PL-259 corrodes outdoors)
• Ground the switch box to your ground system
• Leave a drip loop on all cables entering the switch
• Use direct-burial rated cable for the control line

Stacking Switches (Antenna Combiners)

Stacking switches let you combine multiple Yagis (pointed in the same direction) for additional gain, or select individual antennas for different directions.

A typical contest station might have two 20m Yagis at different heights (50 feet and 100 feet). A stacking switch lets you:

• Use upper Yagi alone (good for DX at low angles)
• Use lower Yagi alone (good for closer contacts at higher angles)
• Combine both (maximum gain, average elevation angle)

How stacking works: Two identical antennas fed in phase combine their patterns, adding approximately 3 dB gain. The phasing harness (coax sections cut to specific lengths) ensures signals arrive in phase at the switch.

Commercial stacking switches:

• StackMatch by Array Solutions: The industry standard. Available for 2, 3, or 4 antennas. Handles legal limit. $300-500 depending on configuration.
• DX Engineering StackMatch Plus: Similar concept, competitive pricing.
• Homebrew: Relay-based combiner with phasing lines. Common at contest stations where operators understand the theory.

What's inside: High-power relays that connect/disconnect antennas from a combining network. The combining network is typically hybrid couplers or simple parallel-feed arrangements with impedance matching.

Band-Pass Filters and Switching

In multi-transmitter environments (Field Day, contest multi-op), band-pass filters prevent one transmitter's harmonics and broadband noise from desensitizing another station's receiver on a different band.

Filter switching systems:

• Array Solutions Bandmaster series: Automatic band-pass filter selection based on radio frequency. Relay-switched filter bank.
• ICE/DX Engineering filter sets: Individual filters per band, manually or automatically switched.
• 4O3A filter controller: Popular in European contest stations. Automatic switching triggered by radio CAT.

When operating multi-multi (multiple operators on multiple bands simultaneously), proper filtering and antenna isolation are essential. Even with antennas pointed different directions, harmonics from a 20m transmitter can destroy a 10m receiver without filtering.

Sequencing Switches (VHF/EME)

Weak-signal VHF and EME stations need precise switching sequences:

1. Antenna relay disconnects from receive preamp
2. Preamp bias removed
3. Antenna relay connects to TX amplifier output
4. Amplifier enabled
5. Exciter keys

All in that order, with proper delays. Reverse sequence on unkey.

Why: Connecting a preamp to an amplifier output (even briefly) destroys the preamp instantly. The sequencer ensures this never happens, even if the operator keys up quickly.

Commercial sequencers: W6PQL design (PCB available), Top Ten Devices, Down East Microwave. These produce timed relay outputs that drive antenna relays, preamp power, and amplifier enable in the correct sequence with adjustable delays (typically 10-50ms between stages).

Receive Antenna Switching

Separate receive antennas (Beverages, loops, flag/pennant antennas) improve reception on 160m and 80m where transmitted noise is the limiting factor.

Receive antenna switching needs:

• TX/RX relay: Automatically disconnects receive antenna during transmit (to protect preamp from your own transmitted RF)
• RX antenna selector: Choose between multiple receive antennas
• Preamp switching: Enable/disable receive preamp as needed

The relay sequencing here is simple: detect TX (via relay line, PTT sense, or RF sense) → disconnect receive antenna and ground it → allow transmit. On unkey: restore receive antenna connection.

Many transceivers have separate RX antenna ports (Icom IC-7610, Kenwood TS-890S, Flex radios) that handle basic RX/TX switching internally.

Homebrew vs Commercial

For antenna switches, homebrew is completely viable:

Relays: Kilovac (now TE Connectivity) vacuum relays handle legal-limit power easily and last forever. Available surplus for $20-40. Smaller DIP relays work for QRP or receive-only switching.

Enclosure: Cast aluminum box (Hammond) provides weatherproofing and shielding.

Connectors: N-type bulkhead connectors for all ports.

Control: Arduino or simple transistor drivers from a selector switch.

Total cost for a homebrew 4-port remote switch: $80-150 depending on relay quality. Compare to $400-600 commercial. The commercial product provides better engineering, guaranteed isolation specs, and warranty — but the homebrew version works fine for most stations.

Common Mistakes

Switching under power: Never switch antennas while transmitting. The relay arc welds contacts together and can damage your transmitter. Always unkey before switching. Most commercial switches include interlock circuits.

Ignoring isolation: A switch with only 30 dB port-to-port isolation lets 0.1% of your transmitted power leak into other antennas. At 1500W, that's 1.5W — enough to damage a receive-only preamp connected to another port.

Wrong connector type outdoors: PL-259 connectors corrode rapidly outdoors. Use N-type for any outdoor installation. The few extra dollars per connector save troubleshooting corroded connections later.

Forgetting grounding: The switch box is a junction point for multiple antennas. It should be bonded to your ground system both for lightning protection and to prevent ground loops.

Undersized control cable: Long runs of thin control cable drop enough voltage to prevent relay actuation. Use 18 AWG minimum for control lines over 50 feet. Or use latching relays that only need a momentary pulse.