"Interface" to attach a "straight" key

No interface is needed - just a simple soldering job - full details supplied.

Interfaces to key an External Oscillator or Rig

Use a diode-protected relay with mains-powered rigs

• RLA: Miniature high-speed relay (not suitable for fast Morse)

• Q1: Almost any low-power NPN switching transistor (e.g. BC108)

• D1, D2: Small silicon diode, +/- 16 volt swing

• R1, R2: The values depend on your equipment, but are not critical. Try 47k (R1) and 100k (R2)

• The collector of Q1 (indicated by "Rig PTT +ve) may be connected to a reverse-voltage diode-protected miniature relay as indicated in the diagram.

#2 - Sophisticated keying interface:
Circuit due to WA5LOD (QST February 1990)

This is suitable for high-speed keying. It is set up for the (usual) positive PTT line. If yours is negative, then reverse the output lines from the opto-coupler and disconnect the line to the transmitter/oscillator chassis, or use a relay.

If keying your rig involves switching a voltage greater than 12V then you must use a relay (with suitable diode protection against reverse-voltage transients) in place of PTT.

If in doubt use a relay. It is assumed that, as a Radio Amateur, you have the competence to wire things correctly. G4UXD can accept no responsibility for the use of these circuits.

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