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Hi fidelity SSB bandwith

Discussion in 'Ham Radio Discussions' started by K1VSK, Feb 27, 2007.

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  1. N3JI

    N3JI Ham Member QRZ Page

    Yeah, I know. I have EQ'ed it for a good amount of low end, so it's there. As opposed to the other clip I just posted...

    [​IMG]
     
  2. N3JI

    N3JI Ham Member QRZ Page

    I'm repeating myself, but this is excellent work. It simulates twisting the BW and/or IF shift knobs on your rig, and I still prefer the 300-4k clip, with the 200-3k & 500-4k being about tied for next. Although the S/N ratio is better using 2.8k, the loss of the top end is quite noticeable.

    I still prefer the ~4k range as a good compromise between BW & intelligibility. That's probably why I'm happy with my 4.2k transmit BW.

    Thanks again for some nice editing work.

    Joe, N3JI
     
  3. N5RFX

    N5RFX Ham Member QRZ Page

    Joe,

    I am glad to be able to analyze these samples. I agree that 4.5 KHz seems to be a good compromise. From 2.8k to 4.5 k you only add 2 dB to the noise, so that should not cause any problems.

    I will work on Ted Koppel's podcast later today using the same setup. I am running out of space on the server I have been using, so some of the links to other samples will start disappearing as we add more.

    73,

    Mark N5RFX
     
  4. K3VR

    K3VR Ham Member QRZ Page

    Yep, that's punchy alright Joe. Contest audio for sure! Thanks for sharing it. And thanks for playing with the other clips too Mark. All interesting stuff for sure.
     
  5. N3JI

    N3JI Ham Member QRZ Page

    BTW, I'm chopping at ~3400 for two reasons: One is I don't think too many folks listen wide enough even with the IF shifted to hear beyond that, and the second is simply to keep the QRM down.  So I could go almost another full kHz, but I'm sure my neighbors on the crowded band wouldn't care for it.

    Joe, N3JI
     
  6. AB0WR

    AB0WR Ham Member QRZ Page

    Very nice.

    Did anyone else notice that they could not tell whether the speaker is saying "pattern" or "patterns" in either of the first two clips?

    The first clip apparently has too low of an SNR, probably because of the wide bandwidth. The second clip just doesn't have enough high freq content to clearly make out the "s" part of the word.

    Yet with the 4khz clips I had no problem telling she was saying "patterns".

    While I like the sound of the 300hz to 4000hz clip better I haven't been able to tell much improvement over the 500hz to 4000hzz clip. You certainly don't get a good "feel" for how she would sound in real life from the 500hz clip.

    Does anyone else notice that or is it just my ears. I do have my hearing aids in. I didn't try listening without them, perhaps I'll do that and see how it sounds.

    tim ab0wr
     
  7. AB0WR

    AB0WR Ham Member QRZ Page

    Ok, without my hearing aids I had a problem hearing the "s" in patterns in all of the clips. My ears, by themselves, make pretty good low pass filters!!!

    I put them back in and I can hear the "s" in the last two clips but not in the first two, at least not very well.

    If someone was using that word in a traffic message it would be very easy for an intermediate relay person to write down "pattern" instead of "patterns". I know it doesn't sound like much but I keep going back to the old "want of a nail" poem!

    tim ab0wr
     
  8. N5RFX

    N5RFX Ham Member QRZ Page

    Now for Ted Koppel. His mail voice does make a difference in the occupied spectrum.

    LPF Cut Off Freq.(Hz) Female (dB) Male (dB)
    200 4.24 6.02
    300 2.53 3.56
    400 2.00 1.68
    500 1.65 1.05
    600 1.43 0.85

    Both male and female speakers voice frequencies are primarily above 200 Hz. The female's frequencies seem to be more evenly distributed than the mail voice. The male voice has a significant amount of spectral density starting at about 300 Hz. In the Ted Koppel sample, the frequency range is limited to 7kHz. This is how I got the file from NPR. I added white noise (0 to 7K) to give a 12 dB SNR.

    There are 4 parts to the Ted Koppel sample.
    1st part: A 60 second sample of the original file with 12 dB SNR.
    2nd part: A 60 second sample of the original file with 6 dB per octave pre-emphasis. The SNR is 14 dB
    3rd part: A 60 second sample of the original file with 6 dB per octave pre-emphasis and 200 - 4500 Hz filtering. The SNR is 16 dB
    4th part: A 60 second sample of the original file with 6 dB per octave pre-emphasis and 200 - 3000 Hz filtering. The SNR is 17 dB
    Ted Koppel Sample
    We have not been considering the affects of AGC. With strong signals, the AGC may be able to drive the noise down below the thermal noise of the receiver. Conversely it is possible that the AGC will not be able to drive the noise below thermal as the bandwidth is widened because of an increase in bandwidth. With only a 2 dB increase in noise (calculated) from 2.8 to 4.5 KHz bandwidth I don't see this as being a problem, and as long as there is sufficient AI gain to the listener, then it is a worthwhile exercise. It is the AI gain that is the most subjective part of the analysis. I really don't have a feel for AI and what differences are significant. That will require some more reading.

    73,

    Mark N5RFX
     
  9. N5RFX

    N5RFX Ham Member QRZ Page

    I heard patterns in all of the clips, but that may be because I heard it first from you. I do recall hearing patterns before you brought it up, because I remember thinking I wanted to look that up in the Internet. I am a Rod Serling fan. My eyes started to go about 3 years ago, and I am waiting for the hearing to go next. I definitely have a family history of hearing loss. Oh boy!

    73,

    Mark N5RFX
     
  10. WD0CT

    WD0CT Ham Member QRZ Page

    Part 1 dull and lifeless. Just like my tv audio on speech.

    The tv has bass and treble boost available from 0 to 100, whatever that means.
    It also has audio presets called
    speech - 20 and 20
    theater - 90 and 90
    concert - 50 and 50
    personal - I set around 60 and 70

    Part 2 highly intelligible but too much for me.

    Part 3 my favorite

    Part 4 hammie audio
     
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