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HEATHKIT

ELECTRONIC KEYER HD-10

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Summary of Contents for HD-10

Page 1: ...HEATHKIT ELECTRONIC KEYER HD 10 ...

Page 2: ...by capacitor C2 to produce a positive 19 volts DC Silicon diode D3 and filter network consisting of ca pacitors C3 and C4 and resistor R9 provides a negative 16 volts DC These voltages are the operating and bias voltages for the transis tor stages KEY SWITCHING The key lever is moved in one direction or the other to actuate switch S1 or S2 Switch S1 turns on the dot generator multivibrator circuit...

Page 3: ...art of the first dot T1 ia at the start of the following space Figure 10 This positive rise is coupled through capacitor C20 to the base of Q1 This drives the base of Q1 to collector cutoff With the collector current of Q1 cutoff the collector voltage increases to its maximum saturation The result is to turn transistor Q2 fully on and Q1 off Although this on and off switching action is fast it is ...

Page 4: ...duct The output from Q7 is fed through resistor R111 to the base of audio clamp Q11 The operation of Q11 will ex plained later The collector output of Q8 is used to key the transmitter This waveform is shown in Figure 12 Figure 12 Manual keying may be accomplished by con necting a hand key between the Hand Key and GND terminals This operates Q7 and Q8 inde pendently of the Keyer operation by shift...

Page 5: ...r that is in the saturated condition In this instance it is Q5 The waveform of the pulse at the junction of C51 and the diode D50 is shown in Figure 14 Figure 14 As Q5 turns off a negative going pulse is pro duced This is because Q5 stops drawing cur rent permitting the collector voltage to become more negative Capacitor C50 is used to pass this pulse to the base of Q4 to speed up the switching ac...

Page 6: ... of the dash is filled in by the next dot signal from Q1 alone as shown in Figure 16 Figure 16 The result of these two signals at he base of Q8 is the waveform shown in Figure 17 Figure 17 At this instant both Q1 and Q5 are on and a space results This completes a dash and a space at the collector of Q8 to key the trans mitter This waveform is shown in Figure 18 Figure 18 As the key lever is moved ...

Page 7: ...lume control is connected to the speaker The control my be adjusted for the desired listening level If desired the receiver output may be con nected between GND and the Receiver Audio terminals This allows the audio to be heard in headphones connected to the Phone jack of the Electronic Keyer The speaker of the Elec tronic Keyer cannot be used when a receiver is connected as it is of too high an i...

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