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Hi fidelity SSB bandwith

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

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  1. K3VR

    K3VR Ham Member QRZ Page

    I can sure see why preemphasis is used when receiver design parameters limit highs to begin with. The energy in the upper 25% of the intelligibility range (3 kHz and up) is well below that of the lower frequencies. Thanks Mark!
     
  2. N3JI

    N3JI Ham Member QRZ Page

    So I popped a cassette tape in my truck's deck the other day...  Yeah, it's been a while since I've listened to cassette tapes, but I was in the mood for some stuff I only had on cassette...  Anyway, it occurred to me that Dolby NR is pretty much what we've been talking about here with the preemphasis/deemphasis.  I never really thought about it before, so I thought I'd drop one more post here for the heck of it.  It's amazing how all this stuff is connected in some way.

    [​IMG]

    Joe
     
  3. WA0LYK

    WA0LYK Ham Member QRZ Page

    You know what, I had forgotten about Dolby NR on my old cassettes. There were times I would turn it off so that the highs came through better, drove the wife crazy though. With some hearing loss, ambient car noise (wind, motor, rear end, etc.), and poor speakers it seemed to make the music sound better, at least to me.

    You are correct though, same kind adjustments to make it more intelligible and/or give it more fidelity.

    Jim
    WA0LYK
     
  4. K3VR

    K3VR Ham Member QRZ Page

    Yep, we've (finally) entered the Dolby age in amateur radio. I'm excited to see what comes next. I hope digital voice can be as good as SSB is right now. If we had the money, we could rent space on low earth satellites and use a digital voice protocol to communicate with each other -- but that smacks of repeater use to me -- and it doesn't give me the thrill of an old fashioned HF contact, which is still like throwing a line in the water and wondering what you might haul in.

    I started in the hobby 31 years ago, listening to AM in the window on 75 meters, and the fidelity was always what I missed in my SSB contacts. Now it's possible to get the same fidelity on SSB using half the space. Ham radio just keeps getting better!

    Thanks for contributing to an excellent thread. The research, the experiments, the dialogue and exchange of ideas -- even the arguments, were all very interesting and informative.

    Til next time,

    K3VR
     
  5. N5RFX

    N5RFX Ham Member QRZ Page

  6. KE4PJW

    KE4PJW Platinum Subscriber Platinum Subscriber QRZ Page

  7. N3JI

    N3JI Ham Member QRZ Page

    LMAO... Me too. In fact, I bought a second double cassette deck a long time ago with dbx because I was afraid I wouldn't be able to listen to all those dbx NR recorded tapes I have (and have them sound right) if my original died.

    Funny thing is I came back to this thread to look up something, forgetting my Dolby NR post. This turned out to be a pretty enlightening thread, if you toss all the bozo comments (on either side of the topic).

    Joe
     
  8. K4KYV

    K4KYV Subscriber QRZ Page

    When the band is congested I chop at 3400~ using a very sharp cut-off brick wall low pass filter. The low frequency response is flat to below 40~.

    Feeding flat-response audio into the speech amplifier sounds somewhat dull and muffled, but by adding pre-emphasis, starting at 800~ and gradually rising to about 9 dB at 2000~, and then levelling out to a flat response plateau up to the cutoff frequency of the filter, the signal sounds clear and crisp, with fairly natural sounding quality. I often get "broadcast quality" reports even with the 3400~ cutoff.
     
  9. N3JI

    N3JI Ham Member QRZ Page

    I'm sure it does sound great that way. However, my reason for cutting the low end is to focus as much power as possible in the range of speech that adds to intelligibility and punch-through. In other words, a full 1500W in the 350-3400 range instead of a lot of that 1500W in the 60-300 range...

    Joe, N3JI
     
  10. KC9JIQ

    KC9JIQ QRZ Member QRZ Page

    WTF [​IMG] you mean the old tapes you had to turn up and down the volume all the time?
    Some of you oldtimers, explain this to me
     
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