The attached has been posted before, but may be helpful. Jim W6JVE -------------- next part -------------- A non-text attachment was scrubbed... Name: Rejuvenation of Carbon Microphone Elements.pdf Type: application/pdf Size: 21999 bytes Desc: URL: <http://mailman.qth.net/pipermail/arc5/attachments/20170414/fc5a6198/attachment-0001.pdf>