2M Transmitter

  
The transmitter was designed specifically for use by radio amateurs as a radio beacon. As such, it provides a good-quality
2M Transmitter - schematic

signal that is free of unwanted harmonics. Transistor Tl, in association with crystal XI, operates as a 36-MHz oscillator. Filter L1/C3 obviates any tendency of the circuit to oscillate at 12 MHz (the fundamental frequency of the crystal). Circuit L2/C4 is tuned to the fourth harmonic of the oscillator signal (144 MHz). This signal is fed to the aerial via a buffer stage that consists of T2, a double-gated FET. The (amplitude) modulating signal is applied to the second gate of the buffer. The output power of the transmitter has been kept low, about 10 to 40 mW. The modulating signal is generated by Nl, an oscillator that switches the transmitter on and off via transistor T3. The switching rate lies between 0.1 and 0.5 Hz. When the output of Nl is low, T3 is switched off, and the transmitter is inoperative because the supply is disabled. When the output of Nl is high, T3 is on and the transmitter operates normally. The digital pattern at the gate of T2 shapes the modulating signal. Gate N2 generates a square wave at a frequency of 0.1 to 1 Hz. As long as the output ofT3 is high, N4 oscillates at a frequency of about 1 kHz. At the relevant gate of N2, there is, therefore, a periodic burst-signal at 1 kHz, and this signal is used to modulate the transmitter. The digital pattern at the relevant gate of 2 can be varied to individual requirements by altering the values of the feedback resistors in the digital chain. The transmitter is calibrated by setting trimmers C4, C7, and C8 for maximum output power. Inductors L2 and L3 are wound from 0.8-mm diameter enamelled copper wire: L2 = 5 turns with a tap of 1 turn from ground; L3A = 3 turns and L3B = 2 turns. The coupling between L3A and L3B should be arranged for maximum output power. The circuit draws a current of only 20 mA, which enables the transmitter to be operated from a 9-V battery for several hours.



News


  • Radio World
    Eric Pere: Generally, operate far more efficiently than DTV or DAB transmitters so, the advantages of water cooling aren't as significant in the FM sphere. If a manufacturer ..... Fewer engineers entering the market today do so as
     23 November 2016
  • Radio World
    The equipment to be provided by GatesAir will be two Flexiva FAX air-cooled 10 kW , antenna systems and auxiliary and support equipment. In addition, a GatesAir Exgine4 HD Radio platform will be installed. The platform, made up of ...
     15 November 2016
  • Radio magazine
    The turnkey system comprises two self-contained FM radio stations with high-efficiency GatesAir Flexiva™ FAX air-cooled 10kW , antenna systems and all auxiliary and support equipment. Bangladesh Betar, the only ... In addition to the
     14 November 2016
  • Radio World
    OTTAWA, ONTARIO — Take an Android tablet computer, a wideband tuner that covers from 100 kHz to 2 GHz, and two audio speakers. Integrate them in a rugged ABS plastic carrying case. What do you have?
     11 November 2016
  • Radio magazine (blog)
    Radio magazine (blog) However, for everyone working on what's inevitably been dubbed “fmexit,” this was welcome validation of the coverage plan and reception characteristics of Norwegian's DAB+ transmission network. On Jan. 11 at
     2 November 2016
  • Radio World
    The manufacturer wrote that the amps are identical to those in certified it makes, and that the transmitters imported and marketed by SCMS “are by all intents and purposes the same models already certified by an FCC approved test lab.&rd
     29 September 2016
  • Radio World
    This is because most systems from the transmitter to the antenna are frequency-specific. This concept may seem foreign to some radio oadcasters. Generally speaking, today's solid-state , filtering, transmission line and antennas are
     14 April 2016
  • Radio World
    This is a two-translator project; open spaces are for gear that is already in operation for the first translator. The equipment seen here includes, from top, an Omnia.7 processor, Audemat RDS encoder and Broadcast Devices switch controller, used
     5 April 2016
  • Radio World
    Radio World Options WidenAs we have reported, Durst Organization is hoping to establish an transmission platform atop the new One World Trade Center downtown, and is seeking oadcaster commitments. Now the owners of the Empire State Buil
     21 October 2014

.