A Mnemonic for CW Cut Numbers

During my Flight of the Bumblebees activation from Block Island, one home station sent me:

2TW

I copied it carefully, sent it back for confirmation, and received RR. I still did not understand it until I was home.

The home-station exchange includes transmitter power. 2TW meant 20 watts:

• 2 was the ordinary numeral 2;
• T was a cut zero;
• W was the literal unit suffix for watts.

Most of my on-air CW has been POTA, where N for 9 in 5NN is by far the cut number I recognize most readily. Encountering T in the middle of a power exchange made me realize that I did not understand the underlying pattern.

Why cut numbers exist

Every Morse numeral normally contains five elements. That is predictable, but it can be slow in a contest or other exchange where both operators already know that a number is coming.

A cut number substitutes a shorter Morse character for the full numeral. The meaning therefore depends heavily on context. Hearing T in ordinary prose means the letter T. Hearing it inside an expected serial number, report, or power value may mean zero.

The mnemonic

When I asked about cut numbers, Josh AC9M pointed out the useful way to think about them: the shorter characters are fragments of the full five-element numerals. A (.-) is the beginning of 1 (.----), while D (-..) is the end of 8 (---..).

From there, the useful rule is:

Except for 5, keep every dit and collapse a run of multiple dahs to one dah. Five is E.

That produces the complete conventional table:

The sequence is also compact enough to remember directly:

T A U V 4 E 6 B D N
0 1 2 3 4 5 6 7 8 9

But the pattern is more useful than the sequence because it lets me reconstruct a character I have forgotten.

For example, 9 is ----.. Keep its final dit and reduce the four dahs to one: -., which is N. Zero is five dahs reduced to one dah, which is T. Two is ..---; keep the two dits and reduce the dahs to one, producing ..-, or U.

What I expect to hear in practice

The full table exists, but three cut numbers account for most of what I am likely to copy:

• T for 0
• A for 1
• N for 9

Andy WI7M pointed out that these three appear frequently in CWTs, where CWops member numbers are part of the exchange. N is also familiar from reports such as 5NN, while T and A commonly shorten serial numbers and power values.

There is related CW shorthand outside the cut-number table. K commonly means one thousand: a station may send K or 1K for 1,000 watts. Andy also abbreviates his TS-2000 as TS2K, since that is much quicker than sending TSTTT. K is an abbreviation for “thousand,” not a Morse numeral substitution in the same sense as A, N, or T.

The remaining cut forms are worth recognizing, but I would not assume every operator expects them. 2TW was valid and efficient, yet unfamiliar enough that I could confirm the characters without understanding the value.

I do not plan to start cutting every number I send. The more useful goal is to recognize the pattern quickly when someone else does, then ask for a targeted fill when the context is still unclear.