How to increase the range of transmission?

Discussion in 'The Projects Forum' started by sudheerelktronics, May 21, 2014.

  1. sudheerelktronics

    Thread Starter New Member

    Jul 8, 2013
    Hi Friends,

    I have recently seen a circuit diagram of FM Transmitter which in shown below:


    Image Resource:

    In this post, it is mentioned that this circuit's transmission range is 2km. I would like to do this project on next week with small modification. I want to improve the transmission range up to 10 km in the above circuit. Is it possible? Can anybody kindly suggest the required modifications for this circuit?

    I will wait for response.
  2. MrChips


    Oct 2, 2009
    If your transmission range exceeds 200ft (61m) you will need a license to operate the transmitter.
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
    you might not need a liscense to increase range in India, which is where he is from.
    a bette antenna would increase the range. how about a better antenna on a tall pole with the transmitter on the pole for short feedline, feed dc and aucio up to the transmitter with shielded wire.
  4. wmodavis

    Well-Known Member

    Oct 23, 2010
    Ways to increase range of a radio communication.

    1. Increase the transmitter output power. This option is what your actual question (Can anybody kindly suggest the required modifications for this circuit?) is geared toward. It might be as simple as increasing the supply voltage or adding an additional RF power amplifier circuit or improving the impedance matching between output stage and antenna.

    Other possibilities for increasing range:

    2. Raise the height of the transmitting and or receiving antenna so there is closer to line-of-site between transmitting and receiving antenna.

    3. Use transmitting/receiving antennas with directional properties hence more gain.

    4. If transmission line is used between transmitter output stage and antenna be sure the line is properly impedance matched and use line with low loss.
  5. enggricha


    May 17, 2014
    @alfacliff I am pretty sure transmissions in the commercial FM band for 10kms is not legal in India.
  6. #12


    Nov 30, 2010
    The page referenced in post #1 does specify 88-108 MHz.
    Surely a problem in the US.
    Does India use 88-108 MHz for the standard FM band?
    I don't know.
  7. DickCappels


    Aug 21, 2008
    One suggestion is to avoid the feedline so that you don't have to worry about matching impedances. There are some pretty nice FM transmitter circuits out there on the web, but they require skill and experience to get them to work properly, to at all in some cases.

    For starters, the link below takes you to a transmitter that should give you 10 km easily :)