[Elecraft] K4 S-meter characteristics

[Wayne Burdick]

We've been making some final changes to firmware associated with the S-meters. Seemed like a good time to summarize how they work.

The S-meters in the K4 have been upgraded from the K3/K3S:

- separate, color-coded S-meters for VFO A and B

- higher resolution (twice as many bars)

- calibration maintained over a wide range of input signals

The two S-meters are calibrated at S9 = -73 dBm (50 uV). As you change receiver front-end gain settings (preamp off/1/2, attenautor 0 to 21 dB) the S-meter level remains virtually constant. Calibration also takes into account the main/sub receiver -3 dB splitters (if engaged) and any slight variations in per-band BPF loss. The upshot is that you get a very accurate signal level indication.

In addition to the S-meters, the K4 provides a convenient way to see signal levels directly in dB (relative). Typically you'd zero the reference level on band noise, then tune into a signal to get the dB increase (S+N / N). This is useful for comparison tests. The numeric values for dB, both main and sub, are shown in the status area of the display, so they don't overwrite VFO B as on the K3/K3S.

In conjunction with these changes, we're updating the "SMH" remote-control command (high-resolution S-meter read) so that it reads directly in dBm.

The S-meters can also be tapped to show the "mini-pan," the K4's high-resolution tuning aid.

Wayne
N6KR