Koch Lesson 4: Add the Letter U

Why this step

U is two dits plus a dah. It collides with S (three dits) if you only hear “a bunch of short tones.” Lesson 4 exists to force that distinction at speed.

What to hear

Wait for the last element. If the group ends on a dah, it is U. If it stays all dits, it is S. R (.-.) has a dah in the middle, not at the end.

Drill

Active set: K, M, R, S, U. Bias extra listens toward S vs U until the last-element test is automatic. The practice link sets lesson=4 so the trainer does not jump ahead.

Letter groups you can type in the translator once the ear is warm: US, RU, MU, SU

Pitfall

Writing “dot dot dash” on paper while listening. Put the pen down; name the letter out loud or click the button.

Practice text

SU US RSU MUS. Ending test: dah after dits means U; all dits means S. Write the last element you heard before naming the letter.

Common mistakes

• Stopping copy after two dits and guessing U — wait for the closing dah.
• Introducing V because it also ends with dah — V is four elements and comes later.

Session notes

U ends with a dah; S does not. Drill this with eyes closed so you cannot see the trainer’s button highlights. Mix US, SU, and RU groups to force attention on the final element. If you operate with a straight key later, the same rule applies: release timing defines the last element, not key shape. Log whether errors happen on send or receive — many learners copy better than they send at this stage. Review Farnsworth settings: character speed should match lesson 1, with optional extra gap between letters only.

Practice schedule

Days 1–2: U versus S with eyes closed. Days 3–4: US, SU, and RU groups. Days 5–6: send the same groups on a straight key or the on-screen keyboard. Day 7: one slow review of every letter in the set. Keep the session under fifteen minutes. If U and S swap, stop the mixed groups and return to that pair until the third element is obvious before you write the letter.

ITU character spacing: three units between letters at full speed.