[R-390] R-390A dB meter as as "S" meter

[2002tii]

Frank wrote:

>Is there any way to equate R-390A dB readings to numeric values on an S-Meter?

Well, whenever the units are dB, which is a relative measurement, the 
question is "dB what?"  S Units are 6 dB apart, and correspond to dBm 
(dB referenced to one milliwatt, 50 ohms) as follows:

S9   -73 dBm
S8   -79
S7   -85
S6   -91
S5   -97
S4   -103
S3   -109
S2   -115
S1   -121

For dB over S9, just add them to -73.  40 over S9 is -73 + 40 = -33 
dBm.  0 dBm is 73 over S9.  The old radioman's saw was "S9 = 50 uV" 
(quite close, for a 50 ohm system.  -73 dBm = 50.2 uV).

390/A meters are generally not calibrated even close to "0" = 0 dBm, 
and even if they were, the metering system is way too crude to track 
at other values.

>I guess if the R-390A dB meter peaks over 50% and copy is clear to 
>my ancient auditory ossicles,
>I'll just say 5/9, rather than try to explain that I like using 
>boatanchors......

In my experience, every ham contact is RST 5-9.  Many times, I've 
heard guys spend 3 or 4 minutes going back and forth repeating "5-9" 
to each other two dozen times before each operator finally 
understands that the report is 5-9.  (Of course, if the reception 
really WERE 5-9, no repetition would be necessary!)  And in the rare 
instance when someone does give less than 5-9, I've heard many 
offended hams lobby for a better report.  Sheesh.

Best regards,

Don