User Manual - Original and Genuine Veronica® Stereo Coder (SCM)


This product is designed and intended for use with a CE/EU marked or FCC compliant transmitter with a MPX baseband audio input of 30 Hz to at least 53 KHz. It should not be used standalone without any enclosure. It is intended to be a: installed inside a broadcast transmitter with other circutry or; b: if used as a stand alone unit, it should be installed in a fully screened EMC enclosure with all input and output connections EMC supressed.

The circuit electronically combines two audio input channels into a single audio output channel usually called Multiplex or MPX. Feeding this MPX into a baseband input at line level (+4dBu) of an FM broadcasting transmitter produces FM Stereo on suitable receivers.


Before attempting any construction, check all the components against the component list. If any of the components are missing or damaged, immediately contact Veronica Kits or your supplier before going any further with this kit. If you are unsure about soldering, see the 'Soldering Tips' section.

The PCB is printed with a legend showing the component shapes and reference numbers (R1, R2, R3, C1, C2, etc). Use the legend together with the component list to find the correct component for the PCB. Take extreme care when placing the components on the PCB. If a component is incorrectly placed, the circuit will not work properly and may even be damaged.

Most of the ceramic capacitors are the surface mount type and these should have been already soldered in. It's normal to assemble the PCB with the smaller components first, progressing through to the larger components. Use the PCB legend as a positioning aid, solder the components into the board and trim back the excess leads in the following order.

1. Resistors.
Flat to PCB with very short leads.

2. Integrated Circuits (IC).
CAUTION STATIC SENSITIVE DEVICES. (Soldering Iron must have good earth. Avoid touching the IC pins with your fingers). Gently bend IC pins with small pliers to allow fit to PCB. Make sure all pins go into PCB and IC is flat down.

Line up with legend for correct polarity. The IC pins are close together, take great care not bridge any of the pins with solder.

3. Variable Resistors.
Keep leads very short and components close to PCB.

4. XTAL, J1, J2 and Electrolytic Capacitors.
Line up Electrolytic Capacitors with legend for correct polarity. All flat to PCB with no leads showing at all. Flat to PCB

5. Phono Sockets.

Before applying a power supply to the circuit, check and double check that all the components are in the correct position with the right polarisation. Check all the soldered joints, these should be shiny in appearance and all components should be rigid. Look carefully for accidental solder bridges and shorts. When all the checks are complete and okay, test the circuit.


R1 47R yellow purple black gold
R2 47R yellow purple black gold
R3 100K brown black yellow gold
R4 47K yellow purple orange gold
R5 4.7K yellow purple red gold
R6 4.7K yellow purple red gold
R7 47K yellow purple orange gold
R8 100K brown black yellow gold
R9 1.2M brown red green gold
R10 1.2M brown red green gold
R11 100K brown black yellow gold
R12 4.7K yellow purple red gold
R13 1K brown black red gold
R14 27K red purple orange gold
R15 27K red purple orange gold
R16 4.7K yellow purple red gold
R17 4.7K yellow purple red gold
R18 4.7K yellow purple red gold
R19 47K yellow purple orange gold
R20 27K red purple orange gold
R21 100R brown black brown gold
R22 100R brown black brown gold
R23 100K brown black yellow gold
R24 4.7K yellow purple red gold
R25 4.7K yellow purple red gold
R26 4.7K yellow purple red gold
R27 4.7K yellow purple red gold
C1 100 pF 101
C2 100 pF 101
C3* 10 uF 10 uF 16v
C4* 10 uF 10 uF 16v
C5 1 nF 102
C6 1 nF 102
C9* 220 uF 220 uF 16v
C7 100 pF 101
C8 100 pF 101
C10 100 pF 101
C11 68 pF 68
C12 1 nF 102
C13 1 nF 102
C14 100 nF 100K 100
C15 1.8 nF 182
C16 100 pF 182
C17 33 pF 33
C18 1.8 nF 182
C19 1 nF 102
C20 10 uF 10 uF 16v
C21 220 pF 221
C22 1.8 nF 101
C23 220 pF 221
C24 1.8 nF 182
C25 1.8 nF 182
J1 3 Way Jumper Connector
J2 3 Way Jumper Connector
VR1 10 K variable resistor
VR2 10 K variable resistor
XTAL 4.864 MHz
IC1* 4060B 4060B 16 pin
IC2* 4013B 4013B 14 pin
IC3* 4016B 4016B 14 pin
IC4* TL074 TL074 14 pin
3 x Gold Phono Socket
1 x DC Connector RED/BLACK





Select the correct Pre-Emph for your country using Jumpers on J1 and J2.


Arrange a regulated power supply or a battery with a voltage between 11 and 16 volts for the circuit. Make the power connection to the PCB using the supplied connector with the red and black wire coming from it.

Connect the MPX OUTPUT to the transmitter input. On Veronica or Aareff transmitters, adjust the audio input level to mid position. Apply a stereo audio source of about line level (775 mV rms) to phono input sockets of the Stereo Coder. Adjust VR1 and VR2 on the Stereo Coder to mid position.

Apply power to the Stereo Coder and Transmitter. Tune an FM Stereo Receiver in to the Transmitter. Your stereo audio source is now 'ON AIR'. The stereo indicator should be active on the FM Receiver. Experiment with the VR1 and VR2 adjustments on the Stereo Coder for the correct levels of audio.


• Audio Inputs Standard Line 0dBu 775mV adjustable
• PCB Mounted Input and Output Audio Phono
• RCA Type Sockets
• Power supply or battery over 11-16V DC
• Pre-emphasis 50 or 75 uS
• Stereo Crosstalk 35 dB min
• Low Audio Distortion, less than 0.01%
• Pilot Tone 19 KHz +/-0.2Hz
• Low Noise, Audio S/N Ratio Better than 70dB
• Audio Response 30Hz to 15KHz +/-0.5dB



Paul Hollings

In Zurgena, Almería, Spain on 01 of November 2008, the equipment:

Original and Genuine Veronica® Stereo Coder (SCM)

Meets the essential requirements of the R&TTE directive and complies with:


All components used in this apparatus are RoHS compliant and do not contain above the specified limits in any of the following restricted substances:

• Lead
• Hexavalent Chromium
• Mercury
• Cadmium
• Polybrominated Biphenyls (PBB's)
• Polybrominated Diphenylethers (PBDE's)


This apparatus must NOT be disposed of with other domestic waste.

We are fully committed to maintaining our responsibilities to the environment. Owners of apparatus that has reached the end of it's useful life can return it to us for recycling, recondition, reuse or proper disposal. You will be required to pay lowest cost postal service available to ship the apparatus to us. Before shipping please contact us for more important information.


It is the customer's responsibility to check relevant laws, directives, regulations and licensing requirements before putting this product into service with an antenna system. You, the customer agree to defend, indemnify and hold harmless Aareff Systems Limited, it's employees and agents, from and against any claims, actions or demands, including without limitation legal and accounting fees, alleging or resulting from improper or unlawful use of this product.



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Every care has been taken in the preparation of this document, errors in content, typographical or otherwise, may have occurred. If you have comments concerning its accuracy, please contact Aareff Systems Limited (UK)