Does the optional Yaesu SSB filter Y-122S provide any meaningful improvement?
YES. The stock filter is a ceramic filter that rolls off somewhat either side of about the center of the passband and has modestly wide skirts. The optional Yaesu SSB filter is a 10-pole mechanical filter by Collins. Its bandwidth is 2.3 kHz and its frequency response is very flat with rather sharp skirts. Measurement of average RF output was about +2 dB greater than that observed when using the stock filter. On-the-air performance reports consistently are that the signal is a couple of dBs stronger and that the audio sounds “cleaner” or more articulate. On receive, the difference between the filters is not very great. However, if the FT-817 has a good quality external speaker attached, the difference in hearing is noticable improved.
