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AMT3000 and AMT5000 AM Radio Broadcast Transmitter Kits

Setting the Quality Standard for High Quality, Low Power, FCC Part 15 Transmitters



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AMT5000 Transmitter Air Check


Here is an actual off-air recording of the AMT5000


>>> Click Here to Listen to the Air Check MP3 <<<

At the beginning, you will hear 4 seconds of low-volume noise, followed by 6 clicks spaced about 2 seconds apart. The clicks are caused by turning the Delco radio frequency knob. The transmitter frequency is set to 1630 kHz. The recording starts with the radio set to 1650 kHz, then on each click, the frequency is changed to 1640, 1630, 1620, 1610, 1620, and back to 1630 kHz for the rest of the recording.




Transmitter Chain

  • Computer playing MP3 files (128 kbps, 44.1 kHz)
  • Winamp v5.621 (x86)
      • Set for monaural output as follows: Ctrl-P->Preferences->Plug-ins->DSP/Effect->Nullsoft Signal Processing Studio DSP v0.39b->Configure active plug-in->Enable processing, Per sample = spl0=(spl0+spl1)/2; spl1=spl0;
      • Winamp volume slider set at maximum
      • Computer volume slider set at 75%
  • MCM Custom Audio Line Level Converter MODEL 555-8485
      • Converts unbalanced consumer line level audio from computer to balanced professional audio line level to transmitter.
      • Using "Left" input and output
      • "Level 2" control set to maximum
  • 100 ft. Cat5 unshielded cable carrying balanced audio and transmitter power on 2 twisted pairs, remaining pairs carry additional parallel grounds.
  • AMT5000 transmitter
      • Located indoors
      • Ground: via 6 ft. wire to AC outlet screw
      • Pro Audio balanced input via 1 twisted pair in Cat5 cable
      • 12VAC power via 1 twisted pair in Cat5 cable
      • Power input adjusted to 100mW
      • NRSC treble boost jumper: ON (enable)
      • Audio processing control settings:
        • GAIN: 12 o'clock
        • MODULATION: 9 o'clock
        • COMPRESSION: 9 o'clock


Receiver Chain

  • Delco model 16194955 car radio modified by Todd Roberts:
      • +- 7.5 kHz IF filter (widens bandwidth to ~10 kHz)
      • Consumer Audio output taken before tone controls
      • Powered by Pyramid model PS-4KX 13.8VDC 3-4A linear regulated
  • Technics model SA-R330 receiver used as amplifier
      • Consumer Audio line input "CD"
      • No equalization
      • Output: "TAPE"
  • Second computer:
      • Audio line-level input from Technics amplifier
      • Software: Total Recorder 8.3 (build 4600) Standard Edition

       Recording mode: mp3, 96 kbps, 44.1 kHz

       Recording level: "Automatically set optimal recording level"





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