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FT-857d Filters

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

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  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 Ham Member QRZ Page


    You are about to cross that " toll bridge "

    Good luck ..

  5. NN4RH

    NN4RH 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 Ham Member QRZ Page

    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 XML Subscriber 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?
  11. K4GUN

    K4GUN Ham Member QRZ Page

    NN4RH, that was an incredibly clear and well written description of a filter. I hadn't given much thought to what a filter actually did. Now I know.
  12. K3UD

    K3UD Guest

    I would suspect that the DSP in the 857d is probably the same as in the FT-100. Using the narrow DSP audio bandwidth for CW can almost take the place of a crystal filter IF you are a casual CW op. It is amazing what the DSP can do with CW signals.

    If you want to participate in CW contests then purchase the 500 hz crystal filter, either the Yaesu or Collins version. The 500hz CW filter working with the DSP audio bandpass filter is an almost unbeatable combination. I also have a 746PRO that is very good on CW, but IMHO the Yaesu FT-100 with the 500hz filter and DSP is the better of the two when it comes to working CW and I would think that the 857d would act the same on CW as the FT-100 does.

  13. VA3SAX

    VA3SAX Ham Member QRZ Page

    if you actually have the 857D model and not simply the 857 then you don't have to worry about purchasing the DSP unit the D model comes with it already just hit the DSP button on the top to bring up the dsp options...I use them a fair bit. I haven't thought so far that the filters were worth paying that much extra dollar for
  14. WA3KYY

    WA3KYY Ham Member QRZ Page

    This is only partially correct. (I also have an 857D) The optional filters are inserted at the second IF whereas the AGC operates at the first IF. This means a strong signal within the passband of the first IF but outside the passband of the second IF can still cause significant AGC action and decreased sensitivity in the presence of strong signals. Only a narrow roofing filter at the first IF can help with that. However, at the frequency of the first IF 60-70MHz, it is very expensive and difficult to design filters narrower than about 4 KHz and even those are very expensive compared to filters designed for IFs of 9Mhz or lower. All radios in this price class that use upconversion to a first IF in the 60-70Mhz range have roofing filters of between 6 and 15 KHz with the cheaper ones having the broader roofing filters.

    The second IF filters do a fine job with signals outside their passband as long as they are not too strong. For folks that do not have another amateur operating legal limit near to them or who operate at field day with more than one station on the same band, they do the job nicely and a narrower roofing filter is not needed.

    Mike WA3KYY
  15. KE5FRF

    KE5FRF Ham Member QRZ Page

    He isn't even a ham yet, give him a friggin break.
  16. KE5FRF

    KE5FRF Ham Member QRZ Page

    Instead of just telling you what kind of filter you need, let's start by edumicating you [​IMG] on what filters do, and why certain modes require certain filters.

    Lets start with sideband, which is primarily a phone mode but is also used to transmit and recieve some digital modes as well. For voice modes, your transmitter and reciever have to transmit a signal of ENOUGH BANDWIDTH to intelligibly reproduce the human voice. The human voice, when modulated on sideband, is roughly 2 kilohertz wide. The low tones in your voice occupy the low end of the audio spectrum, and the high tones in your voice occupy the high end of the audio spectrum, with an ANALOG arrangement of all the tones in between. Now, radios are not required to reproduce the human voice in hi fidelity, so bandwidth is conserved by making the width of intelligibility about 2 KHz, in this way we can fit more signals on the crowded bands.

    A sideband RECIEVER is like a broad barn door, that lets as much of that signal get to your audio stages as possible. Imagine a bunch of horses standing shoulder to shoulder, with the horse on the right being names "High Horse", the horse on the left is named "Bassy Buck" and the horse in the middle is named "Middle-Mare"...a few of their friends are staged along the way to add to the group. All of these horses need to walk through the barn door shoulder to shoulder. Lets say the barn door is too narrow for all the horses. Perhaps Bassy Buck and High Horse will have to stop at the barn wall, and the rest can pass through. Now, imagine each tone of your voice being those horses. With a filter that is too narrow, some of the horses will be left out of the barn.

    When you tune a SSB reciever, you are actually tuning a BANDPASS of frequencies, not just one frequency. The frequency that we say we are operating on is the "zero beat" frequency. This is the frequency where two rigs, tuned together, will sound "natural". If I deviate from that zero beat frequency, it would be like moving my group of horses to far to the left or right of the barn door. The horses on one end will make it through, but the horses on the other end will hit the wall. Depending on which side of the "bandpass" the horses are on, I might hear what sounds like an unintelligible "Donald Duck" (high pitched" minus any bass artifacts) voice, or I might hear what sounds like an unintellible "Goofy", (Bassy without any high tones). Whatever the case, the voice will become more and more unintelligeable as I deviate from the "zero beat".

    Now, for some digital modes, like PSK-31, it is to our advantage sometimes to have a broad passband, like our 2 KHz SSB passband. When the digital signals appear on a spectrum analyzer, we see what is referred to as a "waterfall" of signals. In other words, we can "see" several QSOs within our passband, and we can use computer sound card software to "pick out" our signal of interest. The very narrow world of PSK-31 can exist within only a few KHz of spectrum, with dozens of QSOs takling place where one SSB voice QSO would be!

    CW, or Morse Code, is also a very narrow digital mode, but since we don't normally use computers to send and recieve it, our BRAINS have to be the processors that filter it. Thus, it is very difficult to make heads or tails of several QSOS taking place within a 2000 Hz bandpass. CW operators want to use "narrow doors" to capture the signal of interest. I have a 500 HZ filter installed in my FT-857D. That was a great investment! Before I got it, I'd have QSOs blown away by a strong signal up or down band a few hundred Hz. Your reciever is designed to optimize and amplify strong signals, so when a strong signal is in the presence of a weak signal, it tends to end the QSO quite suddenly. The reason CW only requires a narow filter is because it is but an on/off keyed carrier. It is actually not modulated by audible width, but rather by on/off switching of the key. There is no audio being transmitted, only a carrier at the zero beat frequency. The reciever detects the presence of carrier or lack thereof and generates an audible tone to indicate the pressence or lack therof of the carrier. Our CW filters have to be narrow enough to reject signals that would otherwise be within a SSB bandpass.

    So, to answer your question as well as possible, no, getting a filter AT THIS STAGE is not neccessary, especially if you will be operating casually on SSB. The reciever of that 857d is not so broad that normal day to day SSB operation isn't possible. However, as time goes on, you will have QSOS even on SSB that get wiped out by strong signals adjacent to your operating frequency. You will also want to try contesting at some point. Having narrower filters, within reason, really helps to make an exchange easier to understand.

    Good luck. My 2 cents, I'd get the radio first, and worry about filters later. A lot of aftermarket filters are just as good as the Yaesu Collins filters and a bit cheaper.

    Oh, and the processing is very different from real filtering. The audio is processed and filtered AFTER is has already been demodulated and audio amplified by your reciever. So, if you do not have a narrow IF filter, anything within the bandpass will make it to the DSP. DSPs are not as effective as IF filters and in the presence of interference, will distort a bit. They can be useful tools, especially when interfering signals are weak, and have already been filtered in the IF stage. The DSP can be a suppliment.

    I hope this helps you understand filters better.
  17. W0LPQ

    W0LPQ Ham Member QRZ Page

    FRF don't forget, not all DSP is audio ... my Pro II is IF based DSP .. which is where it should be.

    Bill, W0LPQ/9
  18. KI4WEJ

    KI4WEJ Ham Member QRZ Page

    KE5FRF that has been the best explanation I've received out of all the question I've asked! Thanks a million! From that I think I will hold off for now until I get the feel of the radio a little more. I have a desire to learn the forgotten language of CW so it might be something I need to think about at a later time.
  19. KB0TT

    KB0TT Ham Member QRZ Page


    I gave him a "friggin' break ....

    He is jumping in with both feet and has no " friggin" idea ...

    Instant EXTRA on the way ...

    You had a nice " tutorial " though ...

  20. VU3MES

    VU3MES Ham Member QRZ Page

    hello friends

    i was planning to get a 2.0khz ssb roofing filter for my 857d and this thread was very useful to me. i am going for an inrad 702 filter soon.

    thanks everybody.

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