Ira: Your comments concern me a bit. It is important to remember the electrolet microphone requires a bias voltage but does not consume any electrical power; i.e. you are not powering the microphone. Rather the microphone is modulating the bias voltage. However there may be a current flow within the microphone circuit depending on how the microphone is terminated and coupled to the microphone input circuit. The bottom line is the bias voltage is not important. As long as the voltage rating of any electrolytic capacitors in the network is not exceeded it is not critical. What is important is the quality of the powering circuit. It must be extremely well filtered. One good way of filtering is to use a RC filter in conjunction with a voltage divider. However if you leave out the voltage divider and apply only the RC you will be applying the filter to the mic input rather than to the power source.
When you ask if 10-12v is OK I wonder as to the quality of that power source. If the 12 volts is shared it may well be dirty and unsuitable for a mic circuit. If you are using a 12meg resistor I suspect you may be forming a voltage divider with the leakage resistance of a electrolytic cap. This could damage the cap and not solve your problem. There are plenty of published circuits on how to setup the bias. I would stick with one of them. 73 Fred, AE6QL -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Dr Ira J Saber Sent: Thursday, March 14, 2013 11:46 AM To: elecraft@mailman.qth.net Subject: [Elecraft] CM-500 GA Everyone I hope this has not been answered before, but I could not find my answer in the archives, so here goes. Can anyone tell me how much bias the microphone is able to tolerate? Since the battery pack supplies 3v dc, I am sure that 4-5 volts probable won't hurt. But how about 10-12v DC? I use my headset with my K2, but would like to try it with another rig that supplies 10v. To get my other rig voltage down to the 3-4v region require about 12 meg ohms in series with the 10volts supplied. All of you guys and gals are a great source for info regardless of topic and I wish to thank all and any of you who choose to answer my "novice" question. I have learned something in my years on this earth, that if you don't ask you do not get any answers. Thanks again in advance. 73 Ira N2IS ______________________________________________________________ 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 ______________________________________________________________ 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
