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SS70A 

 5  

 

The audio input is amplified and filtered by the IC, then "mixed" with the 
carrier to produce both the sum and difference frequencies. For example, a 
500 Hz input mixed with the 3 KHz carrier will produce signals at both 2500 
Hz and 3500 Hz and a 1KHz signal will produce a 2 KHz and 4 KHz result. 
The outputs are now low pass filtered to remove the unwanted signals above 
3 KHz. Final result; the low 500 Hz and slightly higher 1 KHz inputs produce 
2500 Hz and 2 KHz outputs respectively. Voila, inverted audio! 
 
The inverted audio is then amplified by either Q1 or Q2, depending on the 
path. On the RX path, J4 jumper position selects either speaker level audio 
from the LM-380 2 watt audio amplifier or line level audio output. 
 
Front panel controls include power on/off switch S1, scramble/bypass switch 
S2, and RX input level select switch S3 which allows the SS70A to be used 
with either line or speaker level inputs. Potentiometer R11 controls audio 
level when speaker level output is selected.  
 

Audio In 

OSC 

IN 

Filter 

Mixer 

Inverted audio 

out 

Audio

 

Osc

 

Sum

 

Difference

 

Desired 

FREQUENC Y 

AMPLITUDE 

Filtered 

 

Spectral display of audio inputs and 
outputs. Sum components are 
filtered, difference components are 
used. 

Summary of Contents for SS70A

Page 1: ...ar to SSB Decodes most cordless phones and basic 2 Way radio systems Loud amplified speaker output no need for an external amp Super clean low noise audio excellent audio quality Accepts mike line or...

Page 2: ...nce Meter RAMSEY AMATEUR RADIO KITS DDF1 Doppler Direction Finder HR Series HF All Mode Receivers QRP Series HF CW Transmitters CW7 CW Keyer CPO3 Code Practice Oscillator QRP Power Amplifiers RAMSEY M...

Page 3: ...5 Parts List 7 Schematic Diagram 8 SS70A Assembly instructions 9 Testing the SS70A 12 Hook up Configurations 13 Troubleshooting 16 Parts Layout Diagram 18 Ramsey Kit Warranty 19 KIT ASSEMBLY AND INST...

Page 4: ...used in the SS70A is adequate to minimize casual eavesdropping or ambulance chasing Greater security is possible using precision audio filters and by inverting more than one audio range simultaneously...

Page 5: ...ed audio The inverted audio is then amplified by either Q1 or Q2 depending on the path On the RX path J4 jumper position selects either speaker level audio from the LM 380 2 watt audio amplifier or li...

Page 6: ...in physical relationship to each other so there s minimal chance of inserting wires into wrong holes Second whenever possible we install in an order that fits our Learn As You Build Kit building phil...

Page 7: ...apacitors marked 100 or 101 C2 11 1 01 uF disc capacitor marked 01 or 103 or 10nF C14 3 1 uF disc capacitors marked 1 or 104 C3 13 16 5 10 uF electrolytic capacitors C1 5 9 12 18 1 100 to 220 uF elect...

Page 8: ...SS70A 8...

Page 9: ...te traces to the top side of the board and over obstacles other traces You will notice that jumpers are normally not found on the schematic but are necessary for proper circuit operation 11 Install C3...

Page 10: ...f the chip is marked with a notch dot or band Check the parts diagram for correct placement Before soldering ensure all pins have made it through the board It s not much fun removing a chip because on...

Page 11: ...rugged and can handle the heat that any pen type soldering iron can deliver 38 Install C1 10 uF electrolytic Be sure to orient the part correctly 39 Install C9 10 uF electrolytic observe polarity 40...

Page 12: ...s connected to power input jack J5 center pin is positive Current requirements are typically 250 500mA which means a decent battery set C or D cells or good quality power supply may be used If you re...

Page 13: ...two way operation where we wish to scramble our outgoing or transmitter audio The RX path through the SS70A is used for receiving and unscrambling the scrambled audio If you are simply using the SS70A...

Page 14: ...and RX paths We ll scramble the audio through the TX path and send it on to the recorder s input to be recorded We ll use the SS70A s RX path to take the recorder s playback audio and unscramble Once...

Page 15: ...udio through the SS70A RX path Due to the large number of types of keying circuits it is best to contact the transceiver manufacturer concerning proper installation of this scrambler in line with your...

Page 16: ...pe can be used to trace the audio signals through the forward and reverse paths of the circuit Loop the audio through the SS 70A having it scramble and unscramble compare to see where a problem lies I...

Page 17: ...pose our manual in the easiest most user friendly format that is possible As our customers we value your opinions comments and additions that you would like to see in future publications Please submit...

Page 18: ...SS70A 18 SS70A PARTS LAYOUT DIAGRAM...

Page 19: ...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 20: ...H INVERSION KIT RAMSEY ELECTRONICS INC 590 Fishers Station Drive Victor New York 14564 Phone 585 924 4560 Fax 585 924 4555 www ramseykits com REQUIRED TOOLS Soldering Iron Ramsey WLC100 Thin Rosin Cor...

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