Single Chip FM Radio Circuit

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This extremely simple FM radio receiver circuit is made possible by the special purpose TDA7000 IC. It integrates nearly all the functions necessary to build an FM receiver needing only a few external capacitors and a tuning circuit. Using a simple active RC filter made of only a single inductor, a few resistors and a varicap, this FM receiver will pick up broadcast radio between about 88 and 108 MHz. The mono output signal can then be used to drive a set of high impedance headphones, or feed a power amplifier.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
C1, C9, C12, C17	4	0.1uF Ceramic Disc Capacitor
C2, C4, C5, C6, C13	5	0.01uF Ceramic Disc Capacitor
C3	1	20pF Ceramic Disc Capacitor	See Notes
C7, C15, C16	3	0.001uF Ceramic Disc Capacitor
C8, C10, C11	3	220pF Ceramic Disc Capacitor
C14	1	100pF Ceramic Disc Capacitor
C18	1	200pF Ceramic Disc Capacitor
R1	1	22K 1/4W 5% Resistor
R2	1	100K 1/4W 5% Resistor
R3	1	100K Linear Taper Pot
D1	1	Motorola MV209 Varicap VHF Tuning Diode
U1	1	TDA7000 FM Radio IC	See Notes
L1	1	7 Turn Inductor (See Notes)
MISC	1	Board, Wire, Socket For U1, Case

Notes

Unfortunately, the TDA7000 went obsolete a few years ago. The original version is made by Signetics (now Philips) and is getting a bit hard to find these days. There are, however, other options. Philips makes the TDA7010T which is a surface mount version. The TDA7021T is also available which includes stereo capability. They are electrically similar but are only 16 pin chips so you'll need to compare the datasheets to build the circuit.

The value of C3 is noncritical and can be between 10pF and 20pF. Minor adjustments to L1 may be required based on the value of C3.

L1 is made by winding 7 turns of 24 AWG wire around pencil. Remove the pencil and then space the turns slightly.

Frequency selection is via R3.

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Comments

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Dan Single Chip FM Radio Sunday, February 14, 2016 9:02:48 PM

Nice, but a bit wide band, and a bit low on frequency, will it do nfm and skip to 137mhz?

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Dan	Single Chip FM Radio	Sunday, February 14, 2016 9:02:48 PM
Nice, but a bit wide band, and a bit low on frequency, will it do nfm and skip to 137mhz?