#516 ZX2031 FM Radio Kit

Building an FM radio kit based on the Silan SC1088 FM receiver chip.

Build

Here’s a quick demo..

Notes

I’m a sucker for radio kits. This time I’ve picked up a small FM kit that has an attractively small circuit board with primarily SMD components.

Most of the heavy lifting is performed by a single chip - the SC1088 in a SOP-16 package.

Ref	Description	checked	installed
IC1	SC1088	√	√
V3	9014	√	√
V4	9012	√	√
V1	BB910	√	√
V2	LED 3mm red	√	√
L1	inductor bead	√	√
L2	choke	√	√
L3	78nH, 8 turns air core	√	√
L4	70nH, 5 turns air core	√	√
EJ	headset	√	√
R1	153 15KΩ	√	√
R2	154 150kΩ	√	√
R3	122 1.2kΩ	√	√
R4	562 5.6kΩ	√	√
R5	681 680Ω TH	√	√
RP	51K	√	√
C1	222	√	√
C2	104	√	√
C12	104	√	√
C16	104	√	√
C10	104	√	√
C3	221	√	√
C5	221	√	√
C4	331	√	v
C6	332	√	v
C7	181	√	√
C8	681	√	√
C9	683	√	√
C11	223	√	√
C13	471	√	√
C14	33	√	√
C15	82pF	√	√
C17	332 ceramic	√	√
C18	100µF electrolytic	√	√
C19	223 ceramic	√	√

kit_parts

kit_pcb_front

kit_pcb_back

The heart of the circuit is the Silan SC1088 FM receiver chip.

Pin	Function	Description
1	Mute	Mute output. Pull down to mute?
2	Voaf	Audio out
3	Loop	AF loop filter
4	Vp	Power 1.8-5.0V
5	Osc	VCO control input
6	IF Fb	IF feedback
7	Clp1	Low-pass capacitor of 1dB amplifier
8	Voif	IF output to external coupling capacitor(high-pass)
9	Vif	IF input to limiter amplifier
10	Clp2	Low-pass capacitor of IF limiter amplifier
11	Virf	signal input 1
12	Virf	signal input 2
13	Cilm	Limiter offset voltage capacitor
14	Gnd	Ground
16	Cap	All-pass filter capacitor. Pull-down for tuning search
16	Tune	Electrical tuning/AFC. Pull-down to reset tuning