Icom Automatic Band Select and Serial Interface

Bob Wolbert, K6XX

16 July 1997

Updated 8 December 1997

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The Completed Project

I have just completed an interface box for Icom rigs that includes a band output port and a CI-V­to­computer serial interface. The band output port drives things like relay-switched DuneStar band filters (Model 600, for example), remote coax switches, etc., and does not require a computer. The CI-V interface allows rig control via computer, and makes logging programs like CT and TR-Log really shine.

Figure 1 is the band select driver portion schematic. When I designed it, I thought I was being really clever--using an IC designed as a consumer-audio output meter as an analog-to-digital converter with an external reference and controlled-current output drivers. Then came the April NCCC meeting: N6TV brought in his OH-made solid state DXpedition kW amplifier, and there in the diagrams was an Icom interface virtually identical to my "clever" circuit. Oh, well, at least this means it should be easy to duplicate and get running for other builders! One major difference from the commercial design is that Figure 1 properly decodes 30m. Unfortunately, other WARC bands are not separated (12m decodes as 10m; 17m decodes as 15m) because Icom's voltage level scheme uses the same voltage for these band pairs.