ATLAS 210 BROADCASTER

This is a very simple device allowing you to transmit what your ATLAS 210 is receiving  in another place .There is a several case where this device is useful .For example it is winter  time , your shack is located beneath the roof , outside temperature is in the 0 deg Celsisus range and it is almost as cold in your station  and you want to hear a  QSO  . If you have not the BROADCASTER  the only way to hear the QSO is to spend several minutes in a cold environment  with the risk of catching  a bronchitis or even something  more terrible . .If you own a BROADCASTER   you only have to  switch on your transceiver ATLAS  and the BROADCASTER   and go in the living room , hearing the qso on your FM receiver  .This is not the only way to use the BROADCASTER .Another very useful usage  is to retransmit directly on your car receiver  all the songs your  have in your MP3 player  by directly feeding the BROADACASTER with the audio coming out of the MP3 player .

THE SCHEMATIC It is outlined on the right . The BROADCASTER is a low power transmitter operating in the FM band anywhere between 88 and 108 mhz so as to be received with any commercial FM receiver .The design of the BROADCASTER is very simple .It uses 2 transistors  (2N3904 ) , the first one operates as an oscillator controlled by  an LC circuit  , the second one is a buffer and  an amplifier .It can be fed with a power supply of 12 to 14 volts .The total consumption is around 20 mA . The oscillator coil has 8 rounds  on 5.5 mm diameter .The polarisation of the oscillator is adjusted by a variable potentiometer  .The frequency modulation is created by directly feeding the oscillator with the audio signal to transmit . Full size schematic

HOW TO BUILD THE BROADCASTER The BROADCASTER  , thanks to its simplicity , can be directly build on  a piece of perforated copper clad .The various components needed are outlined on the schematic (full size) The only adjustment to be made after checking  that the wiring has no mistake is adjusting the potentiometer so as to have a curent between 10 and 20 ma (under 12 volt supply  .The antenna  used to radiate the HF power can be  any length from  10  to  80 centimers

SET UP AND OPERATION The full circuit can find its place in a small plastic box .For convenience especially if you use it in your car the box can be glued  on a  sandard plug  as shown on the left . A small LED is also added to visualized when power is applied .When used is a car there is no need to put an external antenna  as the signal is strong enough  even compared to other FM radio stations on the band .If you want to send up to 100 meter it is better to use a piece of wire as antenna .The length is not critical  . Back to main menu