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Massive Short Wave Amplifier

  1. Aug 26, 2007 #1
    Is there a limit to the possible amplification of Short Wave radio transmission and/or reception? A friend of mine wants to build a massive amplifier / transmitter. If a limit does exist what is the physical law used to explain it?
    Last edited by a moderator: Aug 26, 2007
  2. jcsd
  3. Aug 26, 2007 #2


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    This is a job for Berkeman; he's the local expert regarding ham radio stuff.
  4. Aug 26, 2007 #3


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    The limit starts long before the transmitter is even in the massive category.
  5. Aug 26, 2007 #4


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    It's less a matter of physical law, and more a matter of federal and international law. If you build a transmitter that interferes with other (licensed, legal) communication, bad things will happen. But if you are asking about building a licensed transmitter at maximum power, and what you can do with it, then yes, it will probably fall under the licensed HAM (amateur radio) bands and regulations. I think that about the max power allowed for transmit is 1500W, although there may be some special circumstances that might allow more (I'm not sure). But 1500W transmit power with a good directional Yagi or other antenna, some good skip off of the ionosphere or other high layers, and the right time of day or night, and you can talk a long, long way on shortwave. Usually on the longest contacts, you will use Morse code ("CW"), because you can get a much better signal to noise ratio (SNR) with just the limited bandwidth of the simple audio dots and dashes sounds.

    Tell us more what your friend wants to do, and we can probably help out a lot. Are they a HAM yet? It's gotten much easier in the US recently, as the FCC has dropped the Morse code requirement for obtaining a HAM radio license. They have done this to encourage a wider range of folks to get their HAM license, since the primary purpose of amateur radio HAM operators is to assist local government in emergency communications, which is mostly done with voice communications on the 2 meter and 70 cm bands.

    73, KI6EGL
    Last edited: Aug 26, 2007
  6. Aug 26, 2007 #5
    Thank you so much. I've sent a link to this thread to my friend and he'll be very exited to have connected with an expert on this subject. Maybe he'll even register and speak for himself :)

    Personally, I still am curious about the physical limitations.
  7. Aug 27, 2007 #6


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    Tell your friend to seek out a local ham radio club in your area. We can provide quite a bit of guidance here, but we're no match for a bunch of experienced people gathered around at a club meeting talking face-to-face.

    There are essentially no physical limitations. You could theoretically build (extremely expensive) amplifiers and antenna arrays that could soak up gigawatts of power. It'd be expensive as hell to build, and then one day you'd get the power bill.....

    - Warren
  8. Aug 27, 2007 #7
    Thanks to everyone for the info and advice. I'm really starting to realize the value of this forum and the surprising caliber of some of the members / staff. As I say sometimes at the end of a show "Thanks for not throwing **** at me".

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