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BHI Ltd has a line of DSP products aimed at the amateur radio community. A popular radio modification is to add the NEDSP1061-KBD module inside the radio. It adds a microprocessor and LED to the basic module with a pushbutton that steps through four levels of noise reduction. To take advantage of noise reduction on multiple radios this project uses the basic NEDSP1061-PCB module and offers eight levels of noise reduction. Audio from the radio is fed to a level attenuator, clipping indicator, DSP module, and a power amplifier that drives a speaker and headphones. An alternate source for the TDA7240AV is Futurlec. Also, check eBay for any other parts that have become obsolete.

Good news...the DSP module is now available in the USA from
Gap Antenna for $139.

In response to all interested builders who have indicated that some components are out of stock I have prepared a Revision 1 of this project. Included in the revision is a correction to the schematic sent in by a reader. The affected documents are the Materials List, PCB Layout, and Schematic. New items include toggle switches and the audio amplifier chip. The audio amp is larger and offers even more power than the original. PC boards are currently not available but this may change if enough builders are interested. PC board files are in
ExpressPCB format and you can order your own boards but be aware that small quantities are expensive. Many thanks to N9DYI for building and verifying the Rev. 1 PCB layout.