Hi Gordon,
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The sBitx and zBitx series use a directional coupler to measure SWR and Power:
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From the code, after reading the value from the ATTiny85 vfwd:
? ? sprintf(buff,"%d", (vfwd * 40)/68);
? ? set_field("#fwdpower", buff);
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40/68 is the scaling of the ADC and the 50-Ohm conversion of voltage to power.
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Your comment on accurate power readings is correct.? It will not report an accurate value in anything other than a 50-Ohm load.
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73
Evan
AC9TU
