The Optimod 9100 audio processor is a VERY popular analog, 6-band audio processing system that has been used in AM boradcasting for over 25 years now. It is still a very effective (and my FAVORITE) processor. It is being replaced by newer, DSP-based units such as the 9200 and 9400 series units from Orban/CRL. Bob Orban did an incredible job of designing the 9100 processor and, as they become available on the used market, amateurs interested in broadcast quality audio should seriously consider purchasing these units for AM use on the ham bands. The only drawback is that the 9100 was originally designed for 12kHz audio bandwidth and was later updated by most stations to transmit with the NRSC-recommended bandwidth of 10kHz. While 10kHz audio sounds great, it is, in my opinion, excessive for amateur use (and, most likely, illegal as well.) To that end, I have designed a replacement carfd 1 that replaces the 10kHz filter card and provides steep roll-off above reasonable audio bandwidths. The standard filter bandwidth is 4.5kHz; however, it is also available with a 3.2kHz or 6.0kHz cutoff as well. The filter topology is the same as that I used for the AM Audio Autograph, also viewable on this website. Custom cut-off frequencies are available at slightly higher cost.
The card is "plug and play"; it simply replaces the current card #1, or in some cases, is added to the 9100 mainframe to suppliment it with a Card 1 (original 9100 units do not have a card #1 but do have provision to accept it). In addition, a few resistors are also included that allow optional modification, if the user is willing to do so, of the 4-pole input low pass filter located on Card #4. While not necessary, it does improve the performance of the 9100 when used with reduced bandwidths of 6.0kHz or less.
The board is available in 3 versions. The first version offers a single cutoff frequency. Version 2 allows the "Day/Night" switching control of the 9100 to choose between 2 bandwidths at will; i.e., you could choose 4.5 or 6.0kHz on the fly. Version 3 is a special modification of the dual filter for use with my Exalted Sideband modulation system; more will presented on this in the near future.
For pricing or more information, please feel free to email me. Cards will be on demo at Dayton 2009 and available for delivery by May 30, 2009.