There can be several factors at work, but the main one is that the
effective bandwidth of the P3 is less than the K3. On an SSB signal,
for example, the filter in the K3 passes the entire signal, and that is
what the S-meter reads. However the P3 divides the signal into a nunber
of frequency points on the display, each of which only receives a small
slice of the total SSB signal. A similar thing happens with noise.
However on a narrow-band signal like CW, the P3 and the K3 should agree,
assuming the P3 and K3 are calibrated correctly and the K3's S-meter
mode (CONFIG: SMTR MD) is set for "ABS" (so the S meter doesn't change
when you switch the attenuator or preamp).
There is a more complete explanation in the P3 Owner's Manual in the
section "How to Set Up and Interpret the P3 Display."
Alan N1AL
On 10/13/2013 06:22 PM, Jack Berry wrote:
When operating I see a big difference between the noise floor and signal
indications between the K3 meter and P3 display.
For instance, on 80 meters tonight I see a noise floor of around S2-3 on the P3
and a signal peaking just over S9.
At the same time the K3 meter is displaying a noise level of S9 and a signal
level of 20 over S9.
Is that a calibration error, a result of settings that I have selected - or
just the way things are?
God Bless & 73!
Jack - WE5ST
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