Unlike most condenser microphones (mics), 'RF bias' condenser mics are low impedance devices. This feature makes them especially useful in conditions where moisture can be a problem (outdoors, high humidity environments, etc..).
More details on the concept here: HERE
Sennheiser and Rode offer commercial mics based on this RF principle, but until now there have been very few 'hobby' projects based on the same idea.
This project is an attempt to correct that.... It is a simple circuit, which uses 'off the shelf' IF transformer blanks to create the required inductors - often considered the 'difficult' components in this type of design.
You can find inductor construction details, including source suggestions for the transformer 'blanks'
HERE
This project resulted from a request at the start of THIS THREAD on the 'Group DIY' forum.
My thanks to all those who have contributed to the 600+ posts now in that thread... To Gerard, the thread starter - to Ruud for his prototype PCB layout - to Ricardo and Abbey for their expert suggestions - and especially to Khron for his expertise and patience in designing the various versions of the final project PCB...
• To see project details, just click on any of the headings at the top of the page •