FM RDS/RBDS + AM tuner module

TechDesign Electronics


KIT step-by-step construction guide: Partslist here

Schematic here

 updated June 3, 2009.



 PCB, top view (picture)

These parts will fit on this side of the PCB:     


  • TEF6901AH/v2557 tuner chip
  • 20,5 MhZ precision crystal.
  • Connectors line in/out, power and IC interfaces.
  • coils, filters, transistors, resistors and capacitors.


PCB size = 61,4 x 57,3 mm


Double sided and 100% tested PCB with plated-through-hole connections.

All holes are drilled already.




 PCB, bottom view (picture)

Only a couple of resistors and condensators will have to be soldered onto this side of the PCB.



  Step 1: PCB bottom (drawing)
4 resisitors and 2 capacitors

As said above, only a couple of components here.




4 Resistors:

  • R14...R17: 10K SMD 0805  (103) or (1002) (on-part values)





2 Capacitors:

  • C36,C40: 5pF/5pF6 SMD 0603/0805

  • C1: not needed, leave unconnected.




Step 2: PCB top (drawing)


1 chip (integrated circuit)

  1 Chip:
  • U$1: TEF6901/AH2557 (main chip)


Use a magnifying glass to do the soldering.

First  pre-solder pin1 of the main chip by adding a bit of solder to this pin. Then place the chip onto the PCB and make sure pin 1 is well placed.

The white dot on the drawing point to pin 1 of  the chip. On the PCB, there is a small " " etched near pin 1.








  PCB, top, after step 2 (picture)


Main chip has been soldered.

Check for shorts between the pins and see if each pin is well connected to its pad. Use a  conductivity meter (most multimeters have those) to look into this.

In case you made a short (with the use of too much solder for example) Stay cool (!) and then desolder with  desoldering braid like 3S-WICK or Chem-XIK.



  Step 3: PCB top (drawing)
  6 diodes, 2 transistors, 1 chip

Now we'll have to solder some smaller SMDs.


A good trick is to pre-solder one pcb pad by applying a bit of solder to it. Then place the SMD with the help of a wooden toothpick, whilst soldering the SMD to the pad you've just presoldered. Then solder the remaining pin(s.)


6 Diodes:

  • D1: BB208-03 (A2) (on-part values)

  • D2: BB207 (P13)

  • D3: BAV99 (A7)

  • D4: BAP64-04W (4W)

  • U$2,3: BAP70-04W (1N)

2 Transistors:

  • T1: BF862 (2AW)

  • T2: BC848 (1GW)


1 Chip:

  • U$4: LF85CPT

  PCB, top, after step 4 (picture)
Cleaning of the pcb to remove flux may be done with a PCC (printed circuits cleaner,) Dry with soft paper tissue. Repeat after each step or do it at the end.


Step 5: PCB top (drawing)

13 resistors and 28 capacitors


13 Resistors: SMD 0805

  • R1: 4K7  (472) or (4701) (on-part values)

  • R2: 10K (103) or (1002)

  • R3: 2K2 (222) or (2201)

  • R4: 1K2 (122) or (1201)

  • R5: 22K (223) or (2202)

  • R6: 47K (473) or (4702)

  • R7: 470K (474) or (4703)

  • R8: 82R (820)

  • R9, R11: 560R (561)

  • R10: 1M5 (155) or (1504)

  • R12: 47R (47R0) or (470)

  • R13: 47R SMD 1206  (47R0) or (470)

28 Capacitors:   SMD 0603/0805

  • C11: 270pF

  • C12, C15, C17, C21, C50: 1nF

  • C13: 3n9

  • C16, C37, C38, C48: 22n

  • C18, C19: 6p8

  • C20: 8p2

  • C22, C39, 1F polarized tantalum (105)

  • C23: 100p

  • C24, C27: 10n

  • C25: 220p

  • C29, C35: 220n

  • C33: 27p

  • C34: 47p

  • C41: 2,2F polarized electrolytic

  • C47: 1F

  • C49: 33/47F polarized tantalum (336 or 476)

  • C52: 3n3

IMPORTANT: tantalum capacitors: +pins are marked by coloured band

  PCB, top, after step 5 (picture)

All right, we're making progress!

Most small parts are done now, just a couple to go...


Step 6: PCB top (drawing)

21 capacitors, connectors, 5 coils, etc.

21 Capacitors:   100nF SMD 0603/0805
  • C2...C10
  • C14, C26, C28
  • C30...C32
  • C42...C46
  • C51

8 SIL connectors:

  • JP1: 8-pin (line inputs)
  • JP2: 5-pin (line outputs)
  • JP3: 2-pin (IC)
  • JP4: 2-pin (RDS)
  • JP5: 2-pin (level)
  • JP6: 2-pin (MPX out)
  • JP7: 2-pin (power in +9...12VDC)
  • JP8: 1-pin (Controller, P +3..5VDC pull-up input voltage.)

5 Coils:

  • L1: 51nH variable coil (7mm canned, brown middle) or violet SMD
  • L2: 110nH variable coil (7mm yellow) or blue/green SMD
  • L3: 6H8
  • L4: 15H
  • L5: 1mH

1 crystal, 1 antenna connector, 2 filters and 2 IFTs:

  • Q1: 20.500 MhZ precision crystal
  • U$5: Antenna cinch connector
  • F1: Filter 10.7 MhZ (orientation of the red dot: to the right hand side.) (L10.7S)
  • F2: Filter 450khZ (450GW)
  • TR1: 10.7 MhZ IFT (green/123)
  • TR2: 450 KhZ IFT (white/102)


  PCB, top, after step 6 (picture)


That's it! You now have completed the Tuner module KIT.

Have lots of fun building it!



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