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
- 5, 10 and 100 kHz tuning
- Computer controlled
- Self contained NiMh
- 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
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.