On 3/4/2014 5:32 PM, Don Wilhelm wrote:
The microphone is similar. It is a relatively low impedance source, and it is operating into a relatively high impedance device (1k to 10k for modern transceivers) and the voltage produced is the important parameter. Yes, high impedance microphones may not give the proper frequency response curve, but other than that, no impedance matching is normally required. Modern microphones are in the range of 200 to 600 ohms driving impedance. I suspect yours is also in that range.
Good advice. Almost ten years ago, I bought what was probably a Plantronics salesman's sample kit of five different combo headset mics. I cut the connectors off of them and installed my own XL-connectors, then made adapters to go from the mics to the radios that I owned.
The first task with each headset was to determine which wires went to the earphone and which to the mic. I did that simply by listening to the earset as I measured between wires with an ohmeter. I don't remember how I figured out which wire was common, but I did. :) In each adapter that I built, I added a suitable resistor between the bias terminal on the rig and mic input.
Once I had done that, every headset/mic worked with every radio. Some were more comfortable than others, but all got good audio reports. All of that was long before the K3 even existed. But with the K3, all that is needed is to figure out which wire is which, connect them to the K3, and turn on the bias. They are all electret mics, and electret mics tend to be fairly hot (that is, fairly high output voltage).
73, Jim K9YC . ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
