[Elecraft] K3 S-Meter and Noise

[Dave G4AON]

I have a feeling something may have changed in later K3 firmware,
possibly as a result of calibrating the receiver gain via the K3
Utility. Previously I have been able to calibrate the S-Meter from
around S6 to S9 +60 and have it almost perfect, now it doesn't seem to
be possible to get it that good.

Anyway, these are actual measured results from my K3, which is using the
latest pre-release beta firmware (v3.41). These measurements seem OK to
me and the K3 doesn't seem any noisier than other radios on my 80m
dipole. The S-Meter has been calibrated without the pre-amp in use. It
is quite hard to set it correctly all the way from S1 to S9 +60... AGC
set to default values. SMTR OFF = 027, SMTR SC = 010, SMTR PK = OFF and
SMTR MD = ABS (the latter makes no difference to the S-Meter readings
below).

S1 is solid at -115 dBm, S2 is solid at -109 dBm and S3 is solid at -105
dBm. These are using CW with the pre-amp off on 80m, 2800 Hz filter.
There is about 1 S-point drop using either the 400 Hz or 250 Hz filter.

MDS (3 dB SINAD) is -135 dBm in a 400 Hz bandwidth with the 2800 Hz
filter, pre-amp off. An input of -126 dBm gives 10 dB SINAD for the same
settings. SINAD is signal to noise and distortion.

The K3 is sensitive enough on the lower bands to not need the pre-amp,
which of course would give rise to higher noise levels.

73 Dave, G4AON
K3/100 #80