Note that RT Systems shows a different product to program the FT-817 than for the FT-818. On models that have identical systems, such as the Yaesu FT-897 and FT-837, they sell the same program, in the same package to cover both. I would suggest that there is, as you suggest, some small difference between the two.
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73,
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-Bill Shadid, W9MXQ?