|Amplified electret desk mic|
Not really ever using ssb or other phone modes, this is a strange project for me. When I saw an abandoned, novelty usb desk fan in the bin at work, I could not resist making this little project.
It is basically a electret insert and a single transistor pre-amplifier for which I claim no originality. In fact it is based on a pdf download from Waters and Stanton's website some years ago. A BC182 provides the gain and a few components combined with capacitors for a suitable ssb response, also supplying the voltage for the electret insert, which was bought in a lucky bag at a rally for a pound.
The rest was just a case of squeezing the ugly pcb into the old case and fitting an electret insert onto the boom. This is a piece of plastic tube (empty till roll) into which the insert was bonded, a piece of foam on the end acts like a pop filter. Underneath the battery case supplies the power and there is access to a pot for gain control. The original button on top is used as a push to talk and on the rear a slider switch has been fitted to switch power off when not in use. The mic when powered will also work with a Vox equipped rig.
The gain control has to be carefully set as not to overdrive the rig.
A nice, simple project using a load of old junk!
|Transistor pre-amp and gain pot|
|Battery case, gain pot access and power switch|
|Original circuit by Bob Boddy G6AKL|