Kenwood YF-107CN 270 hz cw filter

Discussion in 'Amateur Radio Equipment Reviews' started by KI4QYI, Jul 21, 2019.

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  1. KI4QYI

    KI4QYI Ham Member QRZ Page

    The first time I used this filter I thought the receiver had gone dead. I discovered if I flipped the pre-amp on and turned the audio gain way up I could hear a noise free but weak signal. Does a correctly working filter like this have such a tremendous insertion loss? I thought a carefully tuned desired signal would come through with near normal loudness. Not so or a defective filter?

  2. KU3X

    KU3X Ham Member QRZ Page

    I am not sure what you are looking for? CW filters don't help pull weak signals out of the band. What they do is narrow the bandwidth down. If there is no interference close to a given signal, by putting the filter in line will not make you hear better or pull in a weak signal that you could not hear before.

    Insertion loss? Yes, there is some. That all depends on the design of the filter. It's usually only a few DB's.

    Go to the wide position in the CW mode on your radio. Tune in a signal. Make sure you are zero beat on the signal. Now put the filter in line. If the signal goes away, turn your VFO a tad to make sure you are zero beat. If you can no longer hear him, you probably have a bad filter.

  3. KI4QYI

    KI4QYI Ham Member QRZ Page

    I bought this filter for my Kenwood TS-480 due to severe overloading of the front end on 40M. For instance, I receive W1AW code practice on 7.0475 Mhz at a signal strength of 10-20 dB over S9. 3 Khz down W1AW is still banging my meter at S5. Now if I carefully zero beat W1AW and switch in the filter the signal disappears off the S meter but can be heard at greatly reduced audio volume. A S5 signal with the filter switched in can barely be heard with the audio all the way up. So I will not be able to pull out any weak signals within 3 khz of a very strong signal which was the desired purpose of the filter. Is such a tremendous insertion loss normal for this type of crystal filter? Maybe it is time to upgrade to a modern base station
  4. KU3X

    KU3X Ham Member QRZ Page

    NO ! You have something wrong. It has been a long time since I installed both CW filters in my 480, but there may be something in the menu you have to change to let the radio know you installed the filter. Make sure all on you solder connections are done properly and no solder Bridges. Use a good magnifying glass to make sure.

    I have two 480's and one has both filters and the other has one. No issues and when they kick in there is no change in the S meter or audio level.

    KI4QYI likes this.
  5. KI4QYI

    KI4QYI Ham Member QRZ Page

    Thank you for responding, Barry! I am going to take the filter out and check everything as you suggested, including menu items first. I do love this radio except for the front end overload on 40 meter cw. I can live with it if I can get the filter working.

  6. KU3X

    KU3X Ham Member QRZ Page

    Make sure your preamp is off.
    If needed, turn on the attenuator.
    For mobile I always leave the RF gain so the bar graph shows S3. I think that equates to 85%?

    The preamp is the biggest mistake people make. They want to see that S meter go as high as they can get it.

    Having the noise blanker on can also create issues. Only use it if you have to. I never have it on at anytime on any radio.

  7. N5CM

    N5CM Ham Member QRZ Page

    I just bought a TS-480SAT (new-to-me) that came equipped with the 1.8 Khz filter. I bought and installed the 500 Hz filter as the secondary filter.

    Well, when I dialed the DSP down below 1000, the signals all but disappeared:(:mad:. I thought I had done a bad job of installing the filter.

    As it turns out, the IF Shift knob was in the 9:00 o'clock position rather than in the neutral 12:00 o'clock position. Once I returned the IF Shift to 12:00 o'clock, everything worked really well, and I'm enjoying the new rig on CW. I can crank the DSP down quite a bit, now and still hear the target signal on CW.

    Check to make sure IF Shift or some other adjustment is not too far one way or the other.

    Gud luck es 73,

    John N5CM
    KU3X likes this.
  8. KI4QYI

    KI4QYI Ham Member QRZ Page

    Stalemate. The filter is definitely bad after rechecking for solder runs and shorts with a magnifying glass. Neither of my desoldering tools will remove enough solder to free the module. So I am stuck with a $120 filter that does not work. Not willing to spend more money on this radio by sending it back to Kenwood for repair. I almost never use the pre-amp except on the higher hf bands and then only rarely. The signal attenuator function lowers the signal but does not stop strong cw signals from wiping out 3 khz of band space below the biggie. All other adjustments are in their correct positions. Thanks for all of the suggestions. I guess I live with it or get a new base station.

  9. WA9UAA

    WA9UAA Ham Member QRZ Page

    Hi Tom,
    Sorry to hear that, the Kenwood boards always seemed to need a bit of cleaning before soldering. I'm wondering if you soldered the tabs on the filter can? I always did but never had a problem, I've had 3 TS 480s and finally went with a IC 7300. (I'd try other radios and went back to the Kenwoods.)
  10. KI4QYI

    KI4QYI Ham Member QRZ Page

    I did solder the tabs. I have had this radio for 12 years and have liked everything but the front end overload when doing cw on 40 meters. I may buy a IC7300 or Kenwood TS590SG ultimately. There is no doubt in my mind that this filter is bad and I am unable to remove enough solder to get it out of the board. The manager at HRO where I bought the radio offered to take a look at it but it is a bit of a drive (3 hours). I loved this radio the first time I tried it there - the controls, display, pleasant audio, good reports on SSB voice quality. Still quite usable except when switching in the filter in CW mode which is only really needed on 40 meters. My qrp rig is not hacking it with current band conditions so I really do need the 100 watts. Not spending any more money on this one. 73, Tom

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