First of all: why should I use filters instead of DSP ? Read my opinion and other information here.
My Yaesu FT-920 came full optional OEM equipped, anyway some of its characteristics were not full satisfying me such as SSB and digital filtering. So I decided to modify the filtering section of CW and SSB adding two INRAD crystal narrow filters in cascade with Yaesu original ones; thank to a special switchboard that INRAD buil for the FT-920 and that can be installed easily inside the cabinet with two filters on it. Now the FT-920 has the possibility to be more selective than before, thank to the high quality of the INRAD filters that have remarkable shape factors
Take a look at the shape factors:
250Hz CW filter
1.8KHz SSB filter
Take a look at the mods inside my radio:
Below you can hear three samples of a CW signal from a Japanese OM that I worked in 30m band using the FT-920. The first recording is the pure signal without filters, the second was recorded with YAESU 500Hz OEM filter switched on and the third with INRAD 250Hz filter switched on in cascade after the Yaesu one. The antenna was my usual 9 meters fishing rod on the top of my building, no IPO and no attenuation were used on the radio.
500Hz YAESU filter
250Hz INRAD filter
Visit websites of other OMs that use INRAD filters inside FT-920: OZ5RZ and T94FC.