One-Plug Filter 2.3-kHz SSB Filter

This excellent filter built by W4RT Electronics contains a 10-pole Collins Mechanical Filter essentially identical in performance to that Yaesu uses in the YF-122S optional 2.3-kHz SSB filter. Proper filter termination is an integral part of rhe W4RT filter assembly. Connectors like those on the YF122C allow you to install and remove this filter just as you do with the Yaesu filter. Filter unit contains the coding for the FT-857 or FT-897 to recognize it as a 2.3 kHz SSB filter. Click here for a link explaining how to install filters in the FT-817. Also see One-Board Filter instruction manual for optimizing performance. Tests have demonstrated that a 2 dB improvement in talk power can be realized by using this filter rather than the stock MuRata ceramic filter. "Hearing" is also improved although you likely will need a better speaker or good headphones to take full advantage of this improvement. Don't be fooled by others offering the 8-pole Collins filter or not having the filter terminated! The following two plots illustrate the response differences between the stock ceramic filter (left) and the SSB Collins Mechanical FIlter (right). It is evident that the Collins filter has a very flat passband and nice steep skirts compared to the ceramic filter. Click here to view a reprint of an article that appeared in QRP Quarterly reagrding both the CW and SSB filters.

A question frequently asked is why isn't there a crystal filter option. The answer has two parts. The first it that crystal filters are physically larger than mechanical filters and are too large to fit into the small space available in the FT-817. The second part has to do with their relative performance. Mechanical filters have lower attenuation in the passband, less ripple, and (as noted above) smaller size for a given performance. Mechanical filters are complicated to manufacture and take 12-16 weeks complete! The operational performance of these filters have been highly respected for almost 50 years! They are very rugged compared to crystal filters. Crystal filters typically have a somewhat better shape factor (more selectivity), but suffer from greater in-band ripple. Nevertheless, both the mechanical and crystal filters provide outstanding performance. The ceramic filters are marginal by comparision.