[AMPS] S-meter calibration

[Court]

As Ian, G3SEK has pointed out, the IARU spec is 6dB/s-unit. However at
least one of the Japanese manufacturers appears to prefer S-meters that
read 5dB/s-unit.
The Kenwood TS-820 was my first experience with a Japanese manufactured
radio. It's S-meter measured quite accurately from S2 to S9+50dB in
steps of 5dB/s-unit. This was of course confirmed by a calibrated signal
generator. These readings held over all the bands covered by the TS-820.
All the subsequent Japanese radios that I have owned (TS-930, TS-940,
TS-950SD, TS-950SDX and currently a TS-870 have all exhibited readings
of 5db/s-unit. To be fair, the S-meter calibration controls had to be
tweaked in order to achieve these readings.
While someone on the list has indicated that the Collins radios were set
up so that S9 at the antenna terminals equaled 100uv, the Collins
KWM-380 radio that I had (in between the TS-950SDX and the TS-870S) was
set up for S9=50uv and followed the 6dB/s-unit spec. Of all the radios
that I have owned over the years, the Collins radio exhibited the most
accurate S-meter readings over its full meter range. 
I have not had any experience with radios marketed by other Japanese
manufacturers but it would appear that at least Kenwood does pay
attention to S-meter readings in designing its HF radios for the amateur
market.    
 
-- 
Court

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