FT 950 narrow IF filter

I am using the FT 950 as a second rig as a backup for my FT 2000. The FT 950 use  the same 450 kHz Ceramic filter as the FT 2000 transceiver . The CF 1001  has been built in the second 450kHz  IF with a BW of about 15kHZ, because the FT 950 can be used in FM as well as in AM mode. 
see: Picture 1

Picture 1: FT 950 IF schematics.

However for SSB and CW the original filter CF1001 -CFWLB450KE1Y is too wide to reduce the signals that are reaching the DSP.( see Picture 2)

 Picture 2: Original IF (Measured on TP 1054, Roofing 15Khz).

Because I don't work on FM and AM mode I decided to install a selection of 2 (two) Murata +/- 2Khz CFWLA450KJFA ceramic filters placed in a cascade.

Picture 3: Murata +/- 2Khz filters placed in a cascade.

Cascaded Murata CFWLA450KJFA filter will reduce much better stopband suppression and bandwidth on SSB and CW is reduced to 4Khz. Therefore it will also reduce IF noise and IF image. FM will be degraded, but AM not excessively.  Normal 2,4 kHz SSB and CW will not be affected. After these changes the signals will be better managed with a DSP.

Picture 4: New bandwith (Measured on TP 1054, Roofing 15Khz).




Preparing the new Cascaded Murata CFWLA450KJFA 4kHz filter for installation:


1. Locate the work area on the PC board (see picture 5)

Picture 5 :  Work area location.

     2. Unsolder SMD resistance R 1415, 0 Ohm (see picture 6)
3. Unsolder SMD resistance R 1433, 390 Ohm (see picture 6)

Picture 6 : 

4.   Stick with glue 2x new  4kHz Murata filters on the existing original  filter CF1001 (see     picture 7).

5.   Connect with a thin  wire the output from a transformer T1027 with the first  new 4Khz     Murata  filter input.

6.   Connect with a thin wire the output from first new 4Khz Murata filter with an input of the     second 4Khz Murata filter.

7.   Solder back with a thin wire the 390 Ohm SMD resistor between the second  Murata  4kHz   filter output and T 1030 input.

8.   Adjust carefully transformers T1027 and T 1030 for maximum S meter deflection 
 (see picture 8).

Picture 7: The final filter installation.

Picture 8 : 450kHz  filter layout and  T1027 and T1030 transformer location.

One Murata CFWLA450KJFA filter has 6dB attenuation, but I did not detect a large difference in signal strenght after the new filter, which has been built in. 
Because the FT 950 receiver is too sensitive on low bands, I decided, after this modification not to increase an IF gain.  However, we can change the IF gain in the FT 950 Hidden Menu setting E01iGN to E10iGn if we want.  (Please see FT 950 Technical Supplement, page Alignment –IF Gain adjustment.)

Please carefully note that this  Hidden service menu is accessible for maintenance for an technician experts. More about the build in procedure can be seen from the pictures.

After building new filters it is still possible to receive AM, but FM will be degraded. I have been testing my receiver in CQWW_2019CW contest with more than 2000 QSOs and I was really satisfied with the new installation.

CFWLA450KJFA filter can be purchased online in Poland at: https://www.hesta.pl/pl/

Picture 9 : Murata  4Khz filter specifications.

Warning !!! Changing any hardware inside FT950 will void your warranty. I am not responsible for any hardware failure. You made this mods on your own risk. This modification requires a high level of soldering skill, possibly beyond that normally possessed by an average HAM. Professional assistance is advised if you are not sure if you have this ability.