Signal Hunt

Tuning changes the pitch, not the volume

This is the one thing that trips up almost everyone at the start. A CW signal is an unmodulated carrier - on its own it is silent. You hear it only because the receiver puts its own frequency alongside and gives you the difference between the two.

So when you turn the knob, the tone slides up or down. It does not get louder. If a station sounds weak and you keep tuning in the hope of improving it, you are moving it out of the filter, not into it. Weak is weak; the answer is a narrower filter or more patience, never more knob.

You can watch this in the tool: the S meter barely moves as you tune across a station, while the pitch swings through hundreds of hertz.

Every station is in two places

Because what you hear is the difference between two frequencies, and a difference has no sign, each station appears twice - once below its true frequency and once above, at the same distance and the same pitch. There is no way to tell the two apart by ear.

That matters when you are counting. A beginner sweeping the band finds eight tones and reports eight stations; there were four. When the tool confirms a catch it names both positions, so you can go back and hear for yourself that they are the same station.

Real receivers offer a second sideband setting to resolve this, which is exactly what an operator reaches for when a band looks impossibly full.

When a narrow filter helps and when it does not

The filter decides how much either side of your listening pitch gets through. Wide open at 2400 Hz you hear a whole neighbourhood at once; at 100 Hz you hear one signal and nothing else. The obvious conclusion - always use the narrowest - is wrong, and the tool will show you why.

• Searching: stay wide. A narrow filter means you can sweep past a station without ever hearing it, because it never lands inside the passband.
• Reading: narrow down, but only after the station sits at your preferred pitch. Narrowing first and tuning afterwards throws the signal out.
• Too narrow too long: at 100 Hz the tuning becomes so touchy that ordinary drift takes the station away from you.

The rule that comes out of this: tune first, then narrow. The confirmation message tells you the narrowest filter that would have isolated your station, so you can compare it with what you actually used.

Why the hint gives a direction and not a frequency

Press the button without the station in your filter and you are told "further up" or "further down". Never a number. A number would let you type your way to the answer and learn nothing; a direction still leaves you to find the edge of the signal by ear, which is the whole exercise.

Turn the band activity up as you improve. On the quiet setting the stations sit kilohertz apart and any filter separates them. On the contest setting twelve stations share the same 40 kHz, several within a quarter of a kilohertz of each other, and there are places where no filter is narrow enough - that is not a fault in the tool, it is what a contest weekend sounds like.