Project: Handheld VHF Receiver

 

 Featured on the cover of QST, February 1999

Design Services Performed:

Description:

This little handheld VHF FM receiver was designed as a demonstration project of using a PIC microcontroller to drive all the functionality of a complete receiver. The receiver features an untuned RF input stage, followed by a double conversion super-hetrodyne receiver. The frequency tuning is accomplished by using a rotary encoder that the PIC reads and translates into programming commands for the 1st LO synthesizer. Tuning steps of 5, 10 and 100 kHz may be selected. The narrow band FM is demodulated by a quadrature mixer and fed to an audio output stage and a small speaker (backside of the unit). The integrated LCD display shows the receive frequency, and received signal strength of any signals. The unit may be tuned manually or can be set to do a full band scanning operation, stopping on active signals then resuming scanning when they disappear. Also included is a full RS232 interface that allows a PC to fully control the receiver and adds a memory scanning feature and a full band Spectrum Analyzer function (see below).

  • 144-148 MHz tuning range with PLL accuracy.
  • RF bandpass filtered input stage.
  • 5, 10 and 100 kHz tuning steps.
  • Computer controlled squelch.
  • Self contained NiMh battery power.
  • Computer control through a integrated RS232 port.
  • Computer control adds full operation, memory scanning and full band spectrum analysis from a PC.
  • PC program written in Visual Basic

Computer control allows three modes of operation: Manual with scanning, Memory scan and a full band spectrum analysis.

Under PC control the receiver can do a full band spectrum analysis.

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