Explain what a speech processor changes, how S-meter steps relate to power, and where your SSB signal sits near a band edge.
Syllabus: Speech processors; S meters; sideband operation near band edges
Compendium articles on the ideas in this lesson, beyond what the exam asks.
Practise the 11 pool questions for this group. Answers are shuffled, and every one comes with a one-line "why".
A speech processor compresses the voice so quiet syllables get closer to the loud ones. The transmitter's peak is the limit, so the average power rises and the voice sounds louder ("talk power"). It does not raise peak power.
Set too high, you get flat tops: distorted speech, excess intermodulation products, and more background noise brought up with the voice.
RememberProcessing: higher average, same peak. Too much: all the bad things.
An S meter shows received signal strength. Each S unit is 6 dB. Above S9 it counts dB over S9.
| Change | dB | Power ratio |
|---|---|---|
| S8 to S9 | +6 | 100.6 ≈ 4× |
| S9 to S9 + 20 | +20 | 102 = 100× |
Remember6 dB per S unit, 4× power. 20 dB over S9 is 100×.
The displayed frequency is the carrier. A 3 kHz signal occupies the 3 kHz below it on LSB, or above it on USB.
| Mode | Dial | Occupies |
|---|---|---|
| LSB | 7.178 MHz | 7.175 to 7.178 MHz |
| USB | 14.347 MHz | 14.347 to 14.350 MHz |
So at a lower edge, LSB needs the carrier at least 3 kHz above the edge. At an upper edge, USB needs it at least 3 kHz below.
RememberSignal extends away from the dial on the sideband's side. Keep all of it inside the segment.