Specifications

one to use yet and because the specifications are so close to the factory installed filter.
FILTER
What sources are available for obtaining the optional filters?
Yaesu and INRAD (http://www.qth.com/inrad/ft-817.htm) are the only commercial sources
at present. Both use Collins Mechanical Filters, but not the same ones. Note that the
Yaesu CW filter is 500 Hz @ -6 db with a shape factor of 4 and the INRAD CW filter is 600
Hz @ -6 dB with a shape factor of 2.5. INRAD also offers a 340 Hz CW filter @ -6 dB
having a shape factor of 2.5. Shape factor = (BW @ -60 dB / BW @ -6 dB). For the SSB
filter, INRAD offers two choices with one identical to the Yaesu YF-122S and the other
provides about 250 Hz more bandwith, Another option is to build your own. K6XX prepared
a quality presentation on how to make your own optional filter using available Collins
mechanical filters. See http://www.k6xx/ft817/817cwf.pdf.
04/09/01-R
FILTER
What are the characteristics of the optional CW filter for the FT-817? Do I need one?
Although the original Yaesu ad for the FT-817 on the inside-rear cover of QST clearly
states that the optional filters are 10-pole Collins filters, the CW filter is actually a 7-pole
filter. Yaesu has determined that the ad was in error and has corrected future ad copy. The
correction first appeared in the April 2001 issue of QST. The Collins part number of the
filter is 526-8686-030. The specifications that Yaesu supplied with the filter are as follows:
Center Freq: 455 kHz, Selectivity (-6/-60 dB): 500Hz/2.0 kHz, Poles: 7 poles, and Dim:
56x9x14 mm. The shape factor is a 4 (BW@-60 dB / BW@-6 dB). How does the filter work
in practice? Simply put, if you work CW, then this filter makes CW enjoyable with this rig.
23/03/01-R
FILTER - SSB
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.
18/06/01
FM MODE
What is the maximum deviation in the FM mode?
The maximum deviation in the FM mode is +/-5 kHz. See TOPIC - FMN MODE also.
15/04/01