I Need Help - AI Part 2312

Prompt: I was rather dreading dealing with a switch that has 80 terminals. I have two alternatives: First: Two switches, one for the minus end and one for the positive end. I can get a 6P5T 6 Pole 5 Position, 3 Deck switch from Amazon, delivered tomorrow, $10 each. Positions marked "0, +1, +2..." and "0, -1, -2..." Second: a bunch of small PC board relays spaced along a project board immediately adjacent to the coils with a single wafer switch carrying 12 VDC power from a wall wart power supply.

Both of these alternatives are massive improvements over the 10-wafer nightmare, and they represent two very different but highly effective design philosophies.

Here is how they stack up for your specific build:

## Alternative 1: The Two-Switch Approach (6P5T)

Using two separate switches—one for the minus (M) sections and one for the plus (P) sections—is extremely practical.

• The Asymmetry Advantage: This perfectly accommodates your idea to use asymmetric tap configurations. You can dial in the exact inductance you need on each side independently. * The Shorting Solution: Because each switch has 6 poles, you have a massive amount of switching logic available on a single shaft. You can easily use one pole to select the active tap, and use the remaining 5 poles to progressively short out the unused outer sections as you turn the dial. * The RF Cost: You will still have to run physical tap wires from the 6-inch coil to the back of the front panel where the switches live. However, managing two distinct bundles (one for M, one for P) is far easier and introduces much less parasitic mess than a single 10-wafer hub.

## Alternative 2: PCB Relays (The Ultimate RF Solution)

From an RF engineering standpoint, the relay board is the superior architecture.

• Zero RF on the Front Panel: By placing the relays immediately adjacent to the coil taps, your RF path remains incredibly short and clean. The rotary switch on your front panel only carries DC voltage, meaning the switch itself introduces absolutely no stray capacitance or parasitic inductance to the receiver circuit. * Total Flexibility: You can wire the relays to handle both the tap selection and the dead-end shorting simultaneously without routing long RF loops around the chassis. * The Power Supply Trap: The only danger here is the wall wart power supply. As you already know from dealing with a house full of smart devices and LED bulbs, standard switching wall warts will inject aggressive hash straight into the SX-28's front end. To power the relays with absolutely pure, zero-noise DC, you can just hook up one of those spare 12V lead-acid batteries you've been running on the pulse repair charger. A dedicated battery keeps the entire matching box completely isolated from the house mains noise, preserving the quiet floor you need for Bands 2 through 6.

## The Verdict

If you want to keep the build entirely passive and don't mind wiring up the 6-pole decks, the two-switch approach from Amazon is cheap, robust, and lets you dial in the asymmetry manually.

If you want the absolute cleanest signal path and the best high-frequency performance (especially up at 42 MHz on Band 6), the relay board powered by a 12V battery is a laboratory-grade solution. You just mount a simple, cheap DC rotary switch on the front panel and let the relays do the heavy RF lifting right next to the PVC pipe.

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Last modified: Sunday, 2 Aug 2026