CW "K" Pip Tone Unit
by John Stockley G8MNY

This is an add on for anyone who wants an automatic CW "K" PIP tone after each over.
This used to be popular for short SSB overs under QSB/QRM conditions like during contests.

Other Morse letters are possible but not exceeding 9 time slots see REPEATERS below.

It has an internal PP3 battery to run the unit while on Tx which is very lightly trickle charged from the PTT line on Rx to maintain the battery.

Features include an LED showing PIP tone is armed (lit during Tx overs) and a "K" LED showing the K leaving.

HOW IT WORKS
The On/Off switch, switches power and also reroutes the PTT line via steering diode D9 (in case the battery is flat). A light trickle charge for the battery via R27 and D10 is taken off the PTT line when on Rx whether the unit is switched on or off and is usuitable for dry cells.

When Mic PTT is low the LED1 lights via R22 and briefly pulses on T1 via C1 and R1 with C2 and R2 providing a power up pulse, T1 resets the ripple counter IC1 ready for the 1st CW clock pulse. The Mic PTT low also turns on PTT drivers T5 via R15 which turns on T6 via R17/18 to repeat the PTT condition to the Rig.

On release of the Mic PTT a long +ve pulse is feed into Gate A of IC2 via R7, C7 and discharged by R8. This enables the oscillator IC2 Gate A and B. With C5 and R10,R11 it oscillates around 27Hz which forms the "dot time" for the CW.

The CW CLOCK is filtered (kept clean on power up etc) with R5 and C3 to feed the ripple counter IC1. The "Q0" pin 3 output line is low from 0-10 count and is used to drive T5 via R16 for PTT as with the Mic while the "K" Pips are generated, and it also drives T2 via R6 to maintain the long CW CLOCK gate ON pulse.

Ripple outputs "Q1" to "Q9" Pins 2 4 7 = dash, 10 = gap, 1 = dot, 5 = gap, 6 9 11 = dash, are diode gated D1-D7 and R9 to make up the timings for the "K".

The +ve CW signals control the AF osc in the same way as the CW CLOCK. The AF oscillator is made from IC2 Gate C and D, and with the C6 and R12/13, it oscillates
around 1KHz.

The square wave AF O/P from IC2D drives T4 via R19 to light the LED2 via R23 to indicate "K" is going out, and also feeds the AF to the Butterworth filter R20/21 and C7/8 to T3 emitter follower, to shape the tone to a near sine wave. T3 is only biased on by the mean DC level of the TTL output when present. T3 feeds the O/P level setting pot VR1 which in turn feeds the K tones to the Mic AF line via a DC blocking Cap C9 and a high value attenuator R24.

IN USE
This is not needed on FM as the squelch tail tells the end of overs quite well.
But for weak fading SSB signals or under heavy QRM it gives a clear unambiguous end of over that can be easily heard.

REPEATERS
Lots more letters are possible for repeaters etc without going into the complexity of computers and Pics etc. here with just a few more diodes and a pull down R per letter.
But don't use more that 2 diodes in series to get a letter. With many letters the load R may need to be increased to 100K. Possible letters are... A,B,C,D,E,F,G,H,I,K,L,M,N,R,S,T,U,V,W,5. Letters that are NOT possible are.. J,O,P,Q,X,Y,Z,1,2,3,4,6,7,8,9,0

A multi way logic selector etc, to select the letter before the AF osc. to give..
No modulation = no CW, K = OK, L = Low Frequency, H = High Frequency, depending on presence of Modulation and FM Discriminator DC output.

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