AM Audio Autograph
Amateur Radio
Audio Processor Project

I am currently building up the first production run of the low pass filter as of 12/23/2008 and expect to have 5 units ready for delivery within the next week or so.  I am building 2 units with a cutoff of 4.5kHz as shown on other pages, 1 unit with a 3.2kHz cutoff for narrowband and SSB use and a pair of units with a 6.0kHz filter specifically designed for W0VMC.  Robert uses a CRL MBL-100 audio processor on the air; I met him through correspondance about the MBL which Gary Clarkson (of CRL) and I designed for use by Radio Free Europe / Radio Liberty in the 1980's.  Robert helped me find an RCA BTA250M transmitter and we had an eyeball in early November, 2008.  At that time, I showed him the prototype 4.5kHz filter and offered one to him if he would test and critique it for me.  He graciously accepted the offer and asked if a 6.0kHz version could be built.  I designed the filter sections as well as the group delay equalizer pair for that cutoff and have since ordered the frequency-determining components.  I plan to finish the unit shortly and deliver it to Robert soon.  The following response curves indicate the performance expected from the finished filter: