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:waving::waving:Welcome to the Best Goldwing Site on the Internet Kevin!:waving::waving:

As for mikes, most cheap units tend to be crystal or piezo mikes, self generating, high output but lesser quality audio. Dynamic mikes mostly have a coil moved by the audio sound waves in the presence of a magnet, basically a speaker used in reverse. The condenser mike is sensitive but has to be in a powered circuit, basically it is a variable capacitor whose capacitance is varied by the incoming audio. High quality but if used on an audio system designed for a different type must have a powered preamp. Often the preamp is built into the mike. Throat mikes originally were designed for aviation, they were carbon mikes that are a variable resistor type. The main purpose was to be able to work in a very high noise environment. There may be other than carbon versions available now, but typically these mikes have poor audio quality.

The idea of having a shunt resistor on the input of an audio amplifier circuit is to dampen any voltages that might be induced in the input wiring. It there is a totally open circuit in the input these voltages have a tendency to set off the feedback oscillation which results in a nasty howl or buzz. They are usually wired across contacts on the back of phone jacks that close when the plug is removed. Not normally used with other types of connectors.

Computers usually use cheap piezo mikes, no power needed. Cellphones easily could use a condenser mike since it's all internal anyway.

Your radio buddy could be right, unshielded wires in a cable can induce feedback from the audio output to the mike input. An impedance mismatch between the mike and the bike's input can also do it. Measuring with an ohm meter only measures the DC resistance which is not directly related to the AC impedance.The muting control on your mike cord may simply short across the mike leads to silence it. If that's the case you wouldn't get feedback then. Have you tested your bike's system with a head set designed for the bike? Before getting too deep in, you might want to verify the bike's system works correctly. If it does it's your headsets, and most likely the mike.
 

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Yep, around 1973 the CB boom was in full swing. It had been available for years before that but the advent of cheaper smaller units and the adoption by truck drivers make a real hot market. The low capacity capacitor (.001uf or so) across the mike was to short out any RF that got picked up by the microphone circuit, the RF could cause all kinds of odd things to happen usually resulting in feedback or poor modulation. I'm afraid it's not that simple in Kevin's case. Getting a reasonable impedance match and proper ioutput level from the mike to the bike'sinput. Decent shielding is important too, the ignition system, and wiring on the bike will generate a lot of noise.

As for looking at the lines on a 'scope I sure spent a lot hours looking at that great old instrument, the Tektronics 545. Before that it was a lot of old crummy 'scopes that didn't even have a calibrated time base. It's amazing to me how small the modern oscilloscopes are now, and how high frequency response they have. I also remember how a lot of 'outlaw CBers' would buy 10 meter ham linear amps and operate around 700W instead of the legal 5W. Ah the grand old days when the electronics were tempermental, bulky, heavy, and expensive!
 

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P=IE E=IR Norton Thevenin Ohms Mhos VTVM Simpson Triplett B&K Fluke HP

Yes, I used to be fluent in the language.
 
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