Audio Processing for AM

Discussion in 'Amplitude Modulation' started by WA3VJB, Aug 30, 2016.

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  1. K5UJ

    K5UJ Ham Member QRZ Page

    Agree with Don, don't mod. the box--use as is--if the action isn't desired use something else.
     
  2. NS5F

    NS5F Ham Member QRZ Page

    There's one data compression scheme for streaming and archiving that is pretty decent. AAC, Advanced Audio Coding delivers a decent reproduction of sound without the high frequency hash of Mpeg audio.
    Don't get me wrong, it's not nearly as good as an uncompressed WAV file but is a decent compromise..
     
  3. G0GSR

    G0GSR Ham Member QRZ Page

    I found an off-air recording of VOA from 1968. (Including a bit of hum)
    Not sure if the UREI 1A was in use at this time or an earlier clipper but it does have a certain characteristic sound that I rather like. (That low-end-intermod grunt! and I'm sure I can hear some phase rotation in there too).

    I remember walking past the TX's at Wooferton and looking at the RF envelope monitors. We called it "Trapezoidal mod" as all the tops were flattened off. Those clippers certainly drove the TX's hard but the old Marconi TX's could take it.
    The Greenwich time pips on the hour were "interesting" as all the TX's radiated them at the same time. We had 6x 250kW at that time so it really used to make the mains sag a bit on the last, long pip.
    Frank, g0gsr
     
    WA3VJB, K4KYV, AC0OB and 2 others like this.
  4. W7TFO

    W7TFO Platinum Subscriber Platinum Subscriber QRZ Page

    KA4KOE and AC0OB like this.
  5. K4KYV

    K4KYV Subscriber QRZ Page

    I can recall when they first started that "new" interval signal, sometime around 1958 or 59. They used to ID the VOA transmitters by callsign, just like a regular AMBC station. Between programs, "This is Voice of America station KCBR at Delano California". Others were WGEO at Schenectady NY, WLWO Cincinnati OH, WRUL Scituate MA, WBOU Bound Brook NJ and a few more. Then sometime later, they added the name of the owner of the transmitter site that contracted out to VOA to the ID: "This is Voice of America station WLWO at Cincinnati OH, operated by the Crosley Broadcasting Company". The musical interval signal came later. Eventually, after the VOA got its own transmitter site in NC, they quit identifying the transmitter call sign over the air.

    Interestingly, some of the VOA transmitters operated at other times of the day as private commercial stations. One I remember quite well was WRUL in MA. When not transmitting VOA programs, they ran their own as "Radio Boston" and IDed as WRUL. Back then, Armed Forces Radio Service (AFRS) transmitted over VOA facilities and included the VOA ID announcements.
     
  6. WA3VJB

    WA3VJB Ham Member QRZ Page

    Frank, that VOA aircheck is well-made, thanks for posting!

    I listened with good earbuds, and agree the nature of the audio has some distinctive processing.

    Also was struck at how formal and stiff-sounding the presenters were, back then.

    The URL to that mp3 roots back to an index with a variety of other sound clips too. Haven't found any liner notes to tell us the receive setup and/or monitoring circumstances. No matter; it stands as a precious audio snaphot from nearly 50 years ago.
     
  7. KM1H

    KM1H Ham Member QRZ Page

    I remember VOA as a propaganda machine once I joined the USN in 59 and learned that the world wasnt flat.

    Their relay station anchored off Rhodes blanketed the Med with splatter, distortion, and harmonics. OTOH they werent the only ones who did that.
     
  8. K5UJ

    K5UJ Ham Member QRZ Page

    KA4KOE likes this.
  9. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Last edited: Jul 26, 2017
  10. K4KYV

    K4KYV Subscriber QRZ Page

    Have retired 222s shown up on the used equipment market at ham-affordable prices or been spotted in BC station garbage cans, making them available for amateur use?
     

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