The indicated noise level depends on the receive bandwidth. For
example, if you use a narrower bandwidth on the K3, you'll notice that
the S meter reads lower.
The effective bandwidth of the P3 is approximately one pixel on the
display, which is SPAN/468. So, for example, if the span is 47 kHz, the
effective bandwidth is about 100 Hz. If the K3 bandwidth is 2.7 kHz,
then the P3 should read 10 * log (2700/100) = 14 dB lower than the K3.
14 dB is roughly 3 S-units.
When measuring a steady carrier, the K3 and P3 should read the same,
since all of the signal is within the bandwidth. The P3's amplitude can
be calibrated with the "Lvl Cal" menu selection.
Alan N1AL
On 03/07/2016 03:14 AM, Brian J. Linn wrote:
All:
Even after considering the P3 manual (page 21) and with AGC off, I find the
following difference in S unit measurement odd.
Band P3 K3
75m S5 S9
10m S0 S2
I'm trying to ascertain an accurate noise level reading at my QTH. Does
anyone have any thoughts on the degree of difference in these readings?
Brian KD0HII
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