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Discussion in 'Electronic Basics' started by Abdul Ahad, Aug 11, 2003.

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  1. Abdul Ahad

    Abdul Ahad Guest

    Can someone please tell me which component to adjust/change to
    increase the range of my 40 MHz transmitter for my remote control car?
    I want to know which BIT inside the transmitter to tamper with...
    (Don't tell me to use a signal booster or better antenna at the
    receiving end, I don't want to do this - I want to boost the

  2. Before you consider doing this, you should do some research.
    Specifically, you need to check with whichever agency in the UK performs
    the same function as the FCC. Specifically, check what the power limits
    are for RC stuff. You could easily end up in deep kimchee if you exceed
    that limit and you get caught.
  3. Guest

    According to the Radiocommunications Agency,

    The limit is 100mW (ERP), which is probably what you're outputting.
    Plus the primary user of the frequency is the Ministry of Defence.

  4. Abdul Ahad

    Abdul Ahad Guest

    O.K. I appreciate the legalities and restrictions on transmitter power
    imposed by government thanks for your information. But I am a "space"
    man with many un-Earthly applications in mind! What if... you were
    stranded on the Moon or on a space station hundreds of miles out in
    space and your life depended on boosting the transmission power of
    your "local" radio - designed for communications only with your
    immediate space/moon based colleagues - so that you could send a
    message to ground control on Earth for a rescue mission? In that
    situation, I doubt if anyone would give a toss about the FCC or other

    I just want to know: do you adjust the CRYSTAL, do you change the
    FERRITE ROD or COIL or do you change another component that dictates
    the output power and the ultimate range of the transmitted signal?

    RSVP - I'm stranded on the lunar surface...!
  5. Sometimes on transmitters, there are resistors which connect to the the
    antenna to cut down the signal, maybe changing those might do something. (I
    have no idea)
    Just don't blame me if something goes bad... :)

    Andrew Howard
  6. Fred Abse

    Fred Abse Guest

    The _power density_ (watts per square meter) decreases as the square of
    the distance, but the _field strength_ (volts per meter) decreases as the
    first power of the distance.

    It's volts per meter at the receiving antenna that matters.
  7. Terry

    Terry Guest

    Thanks Fred. I had some dimly half remembered formula that it had
    something to do with the square of the distance; many things it
    seems have to do with the square or sq. root of things! Also I
    was too lazy to even remember where to look it up!
    What I was trying to help Abdul with was the idea that even IF he
    was able to successfully double the output power of his RCC
    transmitter it would probably have little effect! If his plane or
    model, whatever, went a few yards further away the signal would
    be just as weak as before the power increase. etc.
    Also; in these suspicious times it might be wise, especially if
    one is not an 'electronically skilled person' to NOT tamper with
    something that may have regulatory authority (FCC in the US)
    approval? Terry.
  8. Abdul Ahad

    Abdul Ahad Guest

    Yes, I think I understand the technical intricacies involved here...
    but just one more question: If the radio signals from my 40 MHz model
    transmitter are expected to stay weak no matter how much the power
    amplification, then how do we expect the alien recepients (if any) of
    the 1974 Arecibo Radio Telescope message to respond back???

    For those of us not familiar with this, an interstellar radio message
    was sent to Messier 13, a globular star cluster in the constellation
    of Hercules, on November 16, 1974, from the Arecibo Radio Observatory
    in Puerto Rico. As M13 is 24,000 light years from Earth, and radio
    signals travel at the speed of light, it will take 24,000 years for
    the message to reach the star cluster.

    Abdul Ahad
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