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Radio delay to sync with TV video

Discussion in 'Electronic Design' started by [email protected], Dec 21, 2004.

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  1. Guest

    Ok, posted in electronics.basics but no response:

    Anybody have a simple circut to do this?

    I love listening to our local radio announcers for the game while
    watching the video. However, the radio broadcast is a good 4-5 seconds
    before the HDTV video.

    So I want to delay a radio broadcast by 4-5 seconds. I would imagine I
    would run the tape out to the delay unit, back into the tape in, and
    listen in a monitor mode. A pot that would allow me to change the dlay
    from, say, 0-10 seconds would be beneficial.

  2. On 21 Dec 2004 04:57:21 -0800, in
    Its expensive

    but you could diy with a audio ADC, big chunk of 16bit memory, a few
    counters and audio DAC.
    Not a beginners project


    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
  3. = PC + soundcard + software

    The hardware is trivial, but the software is not a beginners project.

  4. DOH, why didnt I think of that!


    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
  5. On 21 Dec 2004 04:57:21 -0800, in
    following Allans post
    might be worth browsing


    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
  6. Just use a long piece of coaxial cable.
    0.7 nanoseconds per foot.

    Many thanks,

    Don Lancaster
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    voice: (928)428-4073 email:

    Please visit my GURU's LAIR web site at
  7. Jim Thompson

    Jim Thompson Guest

    One over ??

    ...Jim Thompson
  8. Jim Backus

    Jim Backus Guest

    storing the 1,227,600 miles of cable might be a problem though!
  9. Tim Wescott

    Tim Wescott Guest

    Perhaps Don gets very special cable.
  10. Jim Thompson

    Jim Thompson Guest

    Faster than a speeding bullet ;-)

    ...Jim Thompson
  11. Tam/WB2TT

    Tam/WB2TT Guest

    Tape loop should work, but you adjust the delay by changing the spacing
    between the heads. I don't remember what the cassette tape speed is, but
    around 1 ips. So, the spacing would have to be around 4 - 5 inches.

    You could do it electronically with an A/D, D/A converters and some storage.
    For 20 KHz sampling rate you would need 80 - 100 Kwords of storage. Probably
    easier to do it in hardware than sticking a micro in it. Essentially a FIFO,
    where you write in and read out with the same clock, but you don't start
    reading out until the desired number of samples have been stored.

  12. Tim Wescott

    Tim Wescott Guest

    Making an analog audio delay line with a bunch of caps and coils might
    be fun, though.
  13. Jim Thompson

    Jim Thompson Guest

    When I was a student at MIT we had some special coax in the
    Transmission Lines Lab. Its center conductor was a coil so that the
    effective inductance per foot was quite large. I can't quite recall
    now, but I believe it may have had a delay of about 100uS per foot,
    making delay experiments into non-matched loads a piece-a-cake.

    ...Jim Thompson
  14. Tim Wescott

    Tim Wescott Guest

    The only MIT grad that I knew told me they always looked forward to
    playing against WPI, because then they could get there scoring equipment
    fixed by people who could actually recognize a soldering iron.

    Was that the case when you were there?
  15. Jim Thompson

    Jim Thompson Guest

    I had a full scholarship covering tuition and books. But I had to
    cover room and board. So I worked as a technician in Building 20 (but
    I already had some experience... my dad had a radio/TV repair shop and
    a hardware store.

    But most everyone I hung out with at the very least built their own
    kits. (Except for the PhD's who needed help wiping ;-)

    ...Jim Thompson
  16. Guest

  17. Guest

    Tape? What's that? ;-)

    I found the following IC

    Allows for 2 seconds of delay, so I'm sure I could hook up 3 in series
    to accomplish this task... Maybe I'll get it done for next football
  18. Mac

    Mac Guest

    This is not very practical.

    Instead, modulate a laser diode and run the laser light through fiber
    optic cable. The resulting 5 billion or so feet of fiber will be much more
    manageable than the corresponding coax delay line.

    You might still need a couple of repeaters.

  19. Rich Grise

    Rich Grise Guest

    Just go to the nearest Ham club, and ask to borrow their moonbounce
    equipment. You might have to bounce it twice, I guess it's only about two
    and a half seconds per bounce.

  20. Back in the good old days when the BBC started up Radio1, the "pop"
    channel the designs dept came up with an audio compressor that had a
    1mSec LC audio delay line in the signal path so that the gain control
    element did not have to change rapidly, eliminating a lot of pumping
    that you get with fast attack times.


    Serious error.
    All shortcuts have disappeared.
    Screen. Mind. Both are blank.
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