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Ramsey Electronics Model No.       STC1 

Now you can give your home stereo transmitter all of the features 
found in a professional radio station! Control and prevent 
overmodulation, interference from high frequency signals such as 
TVs and older CD players, and “sweeten” the mix with Bass, 
Presence, and Brilliance. A perfect companion for the FM10A and 
the FM25 or any other FM radio transmitter! 

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Gives your station that professional sound with real “Punch!” 

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Ideal companion for FM10A and FM25 

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Requires any DC voltage from 9 to 12VDC 

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Uses line levels from CD players, tape decks, mixers etc. 

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Bass, Presence, and Brilliance controls 

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Dynamic range limiter to prevent overmodulation. 

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15kHz 8th order butterworth low pass filters on each output to 
prevent high frequency interference with the stereo carrier. 

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Clear, concise assembly instructions lead you to a finished product 
that works FIRST time! 

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Add our case and knob set for a finished ‘Pro’ look. Cases match all 
Ramsey products. 

Summary of Contents for STC1

Page 1: ...itter Gives your station that professional sound with real Punch Ideal companion for FM10A and FM25 Requires any DC voltage from 9 to 12VDC Uses line levels from CD players tape decks mixers etc Bass...

Page 2: ...ion Finder HR Series HF All Mode Receivers QRP Series HF CW Transmitters VLF1 Low Bander Low Frequency SWL Converter CPO3 Code Practice Oscillator QRP Power Amplifiers RAMSEY MINI KITS Many other kits...

Page 3: ...5 00 TABLE OF CONTENTS Introduction 4 How Does It Work 5 Learn As You Build 7 Parts List 8 Construction 10 Schematic Diagram 14 Setup And Testing 21 Using The STC1 22 Parts Layout Diagram 24 Parts Va...

Page 4: ...ut simply it means a steep cutoff curve above 16kHz The more orders in a filter the greater the slope of the cutoff curve Butterworth is the name given to the description of the curve s shape A Butter...

Page 5: ...ls are then fed to the limiter circuit This is where a little magic comes into play when you see the two diodes in the feedback path of the opamp As you may know diodes only conduct in one direction b...

Page 6: ...and divided by 4 by U6 A and U6 B to give us 1 5MHz Now we have a cutoff frequency right at 15kHz with very little drifting in frequency There is also an internal opamp inside of U3 which allows us t...

Page 7: ...gently heat the traces to which you are soldering heating both wires and pads simultaneously Apply the solder on the iron and the pad when the pad is hot enough to melt the solder The finished joint s...

Page 8: ...0 ohm resistor brown black brown R47 5 270 ohm resistors red violet brown R40 56 57 60 61 8 1K ohm resistors brown black red R19 43 44 46 48 50 51 54 4 1 8K ohm resistors brown gray red R11 12 36 37 2...

Page 9: ...02uF ceramic capacitors marked 022 223 02 or 203 C8 C31 2 047uF or 05uF ceramic capacitors marked 047 473 05 or 503 C2 20 1 1uF ceramic capacitors marked 1 104 or 100n C44 15 10uF electrolytic capaci...

Page 10: ...lder it in Diode bands electrolytic capacitor polarity transistor shapes dotted or notched ends of IC s and so forth 4 Solder all connections unless directed otherwise Use enough heat and solder flow...

Page 11: ...6 the 74HC74 dual type D flip flop Be careful to observe the correct orientation of this device before you begin soldering Notice the notch indicated in your parts layout diagram This notch correspond...

Page 12: ...want to install this component with the positive lead in the same orientation as shown in the parts layout diagram If you do not install it correctly you will end up with all sorts of problems in the...

Page 13: ...better than 01 accuracy without even aligning it Now we will begin installing the sound processing circuitry which allows us to control bass midrange and highs 44 Install C1 a 100pF ceramic capacitor...

Page 14: ...STC1 14 SCHEMATIC DIAGRAM...

Page 15: ...STC1 15...

Page 16: ...our capacitors many people get confused when they see the positive pin on the parts layout diagram but the negative one is denoted on the part itself and should not be installed in the same hole 64 In...

Page 17: ...triped end of the diode 78 Install D4 another 1N4148 type diode Again check orientation as it is opposite that of D3 79 Install D8 the last 1N4148 type diode Orientation 80 Install R27 a 2 2K ohm resi...

Page 18: ...pin ICs Make sure all 8 pins are through the PC board before soldering and that the part is correctly oriented 102 Install C44 a 1uF ceramic capacitor marked 104 or 1 103 Install C27 a 100pF ceramic...

Page 19: ...nty of solder to mount these RCA plugs This is not so much to do with electrical connection but a physical attachment to the board so they don t break off eventually 120 Install J4 the Right In RCA pl...

Page 20: ...conduct a Locate the supplied hook up wire and cut it in half b Strip both ends of each wire back 1 4 b Solder one wire into the hole marked D7 for the left LED c Solder the other wire into the hole m...

Page 21: ...ny errors 1 Check Pin 4 of U1 for 10 volts DC 2 Check Pin 10 of U1 for 5 volts DC 3 Connect your oscilloscope probe to pin 9 of U6 Verify that there is a good clean square wave at 1 5MHz This means th...

Page 22: ...s just compare your sound level to that of adjacent radio stations on a good FM receiver Just adjust the levels until they sound about the same The most fun part of this kit is custom tailoring your s...

Page 23: ...STC1 23 EXAMPLE HOOKUP...

Page 24: ...STC1 24 PARTS LAYOUT DIAGRAM...

Page 25: ...STC1 25 PARTS VALUE DIAGRAM...

Page 26: ...inputs then trace through the circuit with the probe When you have gazinda input with no gazada output you will then know where the problem lies PROBLEM The sound is distorted before the LEDs light S...

Page 27: ...h be assured that the 1K ohm resistors are actually the missing 10 K parts Hum m m I guess the red band really does look orange Ramsey Electronics project kits are packed with pride in the USA If you...

Page 28: ...Publication No MSTC1 Assembly and Instruction manual for RAMSEY MODEL NO STC1 STEREO TRANSMITTER COMPANION KIT REQUIRED TOOLS Soldering Iron WLC100 Thin Rosin Core Solder RTS12 Needle Nose Pliers MPP4...

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