FRM-Stereocoder

This schematic originally comes from a Dutch magazine called Free Radio Magazine 1-1983 and was designed by Alfred Debels. It's very easy to build and gives fair results. For the best performance you should better use lownoise OPAMPS like the LM356 than the uA741 and use metalfilm types for all resistors.





The FRM coder as built by stern





Partslist:

Resistors 1/4Watt metalfilm Semiconductors Capacitors
1x 1E 1x 74LS00 1x 40pF tunable
3x 390E 1x 74LS390 1x 47pF styroflex
1x 470E 1x CD4027 1x 100pF styroflex
2x 560E 1x CD4066 or 4016B 1x 150pF styroflex
1x 1k potentiometer 4x LM356 or uA741 4x 470pF styroflex
1x 1k8 1x TUN (BC547 or equal) 2x 1n2 MKT
1x 3k3 1x Zenerdiode 5.1[V] 1x 3n3 MKT
2x 8k2 3x 10n ceramic
1x 10k potentiometer Others 1x 15n MKT
2x 10k 1x 18mH coil 1x 22n MKT
5x 12k 1x 33mH coil 1x 100n ceramic
1x 15k 1x X-tal 7.6[MHz] 2x 2.2uF/25v elco
1x 25k potentiometer 2x 4.7uF/25v elco
5x 33k 1x 250uF/6-10V elco
2x 47k
1x 82k
1x 150k
1x 220k
1x 560k
1x 680k

A possible PCB is giving here: