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Ignition system
to suit bike

I need an ignition system to suit my bike. It has one pickup coil mounted at the crankshaft which I think is a Hall effect coil and it has only two wires going to it. The trigger plate is a half-moon shape and I think it triggers the IC igniter twice per revolution of the crankshaft.

The bike has two ignition coils firing four cylinders, so the igniter has to treat the coils as separate units to fire each one individually. The coils each have two plug leads so if cylinder number 2 is on the compression stroke, number 3 is on exhaust, so only number 2 is firing.

This system is a typical late-model 4-cylinder Japanese system for a motorbike. The trouble is I cannot adjust it because it is all sealed up. I need to build two of these systems as I have a race bike as well. (M. E., via email).

• If your bike uses a 12V battery for its original ignition, you could use the Programmable Ignition System described in the March, April and May 2007 issues. Two would be required, since you effectively have two ignition systems. The reluctor input version will operate on the magneto trigger.

If your bike does not use the battery for ignition but uses a high-voltage coil to generate power for a capacitor discharge unit, then you could use the replacement module featured in May 2008. Note that the trigger for your coil and magnet is most likely a magneto trigger and not a Hall effect sensor.

Quarter Second Pulser For GPS Clock

The GPS clock in the March issue looks like an interesting project but my clock seems to advance in quarter second intervals. Any chance of devising a simple circuit using a 555 timer say to deliver four pulses per second and still be kept in sync with the 1-second pulses from the project?

Another item I have been meaning to ask about concerns a distortionless AM demodulating process I read about in the 1960s. It was called the “synchrodyne”. The process relied on mixing an unmodulated carrier wave of the same frequency as the RF carrier back into the AM RF signal.

Sum and difference beat frequencies would be produced and the key issue is that the difference frequencies are exactly the audio signal which can be separated out from the higher RF components with a simple LP filter.

The problem with such an approach back in the 1960s was to get the injected unmodulated carrier to be exactly the same frequency as the RF signal. This problem was a big stumbling block back then but these days, with readily available crystals and phase locked loops, it might be more practical. But I suppose with the advent of digital radio interest in AM is fading fast. Have you ever come across this type of AM detection?

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