ad: rfparts

FT-857d Filters

Discussion in 'General Technical Questions and Answers' started by KI4WEJ, May 28, 2007.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: K3QNTad-1
ad: L-rfparts
ad: Subscribe
ad: l-gcopper
  1. KI4WEJ

    KI4WEJ Ham Member QRZ Page

    What will these filters do for my radio?

    DSP-2 Digital Signal Processing Unit
    YF-122C Collins CW Filter 500 Hz, 7-pole
    YF-122CN Collins CW Filter, 300 Hz, 7-pole
    YF-122S Collins SSB Filter 2.3 kHz, 10-pole

    Are they worth the money?
  2. K8JD

    K8JD Ham Member QRZ Page

    They control the bandwidth of your reciever!
  3. KI4WEJ

    KI4WEJ Ham Member QRZ Page

    Ok so the YF-122CN and the YF-122S will narrow the receiving band for each one of the designated modes? What good will that do? Seems like it would make it harder to obtain the signal.

    What about that DSP-2?
  4. KB0TT

    KB0TT Premium Subscriber QRZ Page


    You are about to cross that " toll bridge "

    Good luck ..

  5. NN4RH

    NN4RH Premium Subscriber QRZ Page

    For example, in the CQ WPX CW contest this weekend, when things would get crowded there would be stations operating very close together, say 300 Hz.

    With the default filter that comes with the rig, generally a 2.7 kHz filter meant for SSB, you'd be hearing around nine CW signals in the pass-band and you might have a hard time copying the one you're interested in, especially if you're interested in a weak one when there's one or more strong ones near by.

    With a 500 Hz filter you'd be able to hear only one or two stations at a time making it much easier to copy the one you're interested in. With a 300 Hz filter, you could narrow it down to one signal.

    Those CW filters go into the IF portion of the circuit, so that the audio stages are only amplifying the signal you're interested in.

    The DSP unit on the other hand works on the audio stage. It provides for some filtering and noise management in the audio stage, but it's not as effective in the AF stages as doing it in the IF stage.

    IF filtering also helps with signal to noise ratio when you do only have one weak CW signal. Rather than having to listen to 2700 Hz worth of noise, you only have to listen to 500 Hz or 300 Hz worth of noise.
  6. KA5S

    KA5S Subscriber QRZ Page

    1) Help reception. The DSP can be set to lower "white" noise, narrow the bandwidth and automatically reject single-tone interference. The others provide narrower bandwidth and steeper skirts than the stock filters.

    2) MENU MODE No-088 [TX IF FILTER] allows selecting an optional filter to transmit through. W4WB's site notes for a 2.3 KHz filter (they sell practically the same item) "a 2-dB improvement in talk power can be realized by using this filter rather than the stock MuRata ceramic filter." Similarly, you can use a narrow CW filter in Data mode to reduce problems from harmonics of the audio signal being transmitted when running AFSK sound-card and TNC modes.

    If you do any CW at all you really need a narrow CW filter. I don't know that 300 Hz is a better value than 500, though, and it (300 Hz) may not pass all of the sound-card modes you'd want to try.

  7. KI4WEJ

    KI4WEJ Ham Member QRZ Page

    Ok so If I wanted the narrowest filter I could get just the YF-122CN Collins CW Filter, 300 Hz, 7-pole? Would that eliminate the need for the YF-122S Collins SSB Filter 2.3 kHz, 10-pole or would I still need that to narrow the SSB mode?
  8. AG3Y

    AG3Y Guest

    If you want to have better than stock filtering for BOTH SSB and CW, you would have to get both filters. The 2.3Khz filter would be too wide for CW use, and the 300Hz filter would be too narrow for SSB!

    However, unless you are really in to contesting, you might find using a narrower SSB filter in conjunction with a bandpass tuning feature of your radio totally adequate.

    I have a 3.5Khz filter for SSB, and a 300 hz filter for CW in my main station rig. However, the rig also has bandpass tuning, and if I turn it down to the narrowest setting, I can hardly hear a difference between switching the 300hz filter in or out. There is some difference, but it is not all that noticeable.

    I would certainly try the rig without the extra filters, and see if the performance is adequate for your purposes. You might be able to get some other nice system accessory with the money you would save on the filters!

    Good luck! 73, Jim
  9. N4CR

    N4CR Ham Member QRZ Page

    I also have an FT-857D, and I find that the front end of this receiver is very wide. This means that a signal outside our immediate bandpass can affect our AGC even though we are not tuned to them.

    So, say you are listening to a signal that is pretty weak and a giant signal shows up 10kc away. On an FT-857D, it's very likely that he will make the weak signal completely disappear.

    With the optional filters installed, you can reduce the effect of nearby signals that you don't want to hear. They are VERY effective at doing this and are worth the money if you need to work crowded conditions with strong nearby signals, like field day or similer.

    I use the 300hz filter for PSK31. It makes it so that stronger signals in the normal passband are no longer being decoded, making the decoding better and improving my Signal to Noise on weak signals. If I had AGC on, it would help eliminate the signal pumping, but I generally run PSK with the AGC off and use the RF Gain control to fine tune after I tune the 300hz filter.
  10. K4AX

    K4AX Ham Member QRZ Page

    So, what would a 2khz filter gain you, and what would be the con?  Would it help on TX as well, with a bit less audio quality as a negative?

    Would the 500hz filter be good for PSK31 and be more usefull in other data modes?
Thread Status:
Not open for further replies.

Share This Page