QUICK TONE CTCSS SUB - AUDIBLE TONE ENCODER DECODER Ramsey Electronics Model No. QT1 Caught in the maze of low frequency tones? Looking for an easy way to update your rig with sub-audible frequency tones? Let the Ramsey Quick Tone do the job for you with digital accuracy! • Sharing a channel using (C)ontinuous (T)one (C)ontrolled (S)ubaudible (S)quelch or PL ? This is the complete circuit solution for you! • Mini size quality circuit board designed to fit inside many transceivers.
PARTIAL LIST OF AVAILABLE KITS: RAMSEY TRANSMITTER KITS • FM10A, FM25B FM Stereo Transmitters • AM1, AM25 Transmitter RAMSEY RECEIVER KITS • FR1 FM Broadcast Receiver • AR1 Aircraft Band Receiver • SR2 Shortwave Receiver • AA7 Active Antenna • SC1 Shortwave Converter RAMSEY HOBBY KITS • SG7 Personal Speed Radar • SS70A Speech Scrambler/Descrambler • TT1 Telephone Recorder • SP1 Speakerphone • MD3 Microwave Motion Detector • WEB1 Walking Electronic Bug • ECG1 Heart Monitor • PG13 Plasma Generator • TFM3 Tri-
Ramsey Publication No. MQT1 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR QUICK TONE CTCSS SUB - AUDIBLE TONE ENCODER DECODER TABLE OF CONTENTS Introduction to the QT1 ................. 4 How it Works ................................. 4 Schematic Diagram..................... 10 Parts list ........................................ 6 QT1 Assembly Instructions ........... 7 Parts Layout Diagram ................. 11 Hook-up Configurations ............... 12 Troubleshooting ...........................
INTRODUCTION With todays’ ever shrinking radio frequency spectrum, it has become common place to “share” radio frequencies using a tone squelch arrangement. By transmitting a low frequency audio tone (sub-audible to the radio and most of us) we can enable our transmitter to connect with receivers specifically listening for the particular tone one happens to use. This will eliminate much of the background “chatter” that may also be taking place on a desired frequency.
received audio until the sub-audible tone is detected. When that occurs, transistor Q1 is turned off and the audio signal is free to drive a speaker or headset output. Another receive audio path is directly through the MX-COM. IC. The received audio is routed through an internal high pass filter which digitally filters out any low frequency CTCSS component in the received audio.
QT1 PARTS LIST Please check the boxes after the components have been identified, and it is also handy at this time to “sort” the like components into groups or bins (an egg carton does nicely) to avoid using the wrong component during assembly.
RAMSEY Learn-As-You-Build KIT ASSEMBLY There are numerous solder connections on the QT1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your kit! • • • • Use a 25-watt soldering pencil with a clean, sharp tip. Use only rosin-core solder intended for electronics use. Use bright lighting; a magnifying lamp or bench-style magnifier may be helpful. Do your work in stages, taking breaks to check your work.
2. Insert it into the correct PC board location. 3. Orient it correctly and follow the PC board drawing and the written directions for all parts - especially when there's a right way and a wrong way to solder it in. (Diode bands, electrolytic capacitor polarity, transistor shapes, dotted or notched ends of ICs, and so forth.) 4. Solder all connections unless directed otherwise. Use enough heat and solder flow for clean, shiny, completed connections.
5. Identify R2, 470K ohm (yellow-violet-yellow). Notice how this component will be mounted “standing up”. To mount this component properly, you’ll need to form the leads as shown. Then slip the leads though the circuit board, and solder. 6. Install R3, 820K ohm (grey-red-yellow). Notice that this component is also mounted “standing”. By mounting the components this way they occupy less room on the PC board, making our finished project as small as possible. 7. Install D2, a 1N4148 type diode.
18. Install C8, 68pF disc capacitor (marked 68 or 68K). 19. Install C1, 1uF electrolytic capacitor. Ensure proper polarity. 20. Identify and install diode D1, 1N4002 (epoxy bodied component with stripe, marked 4002). Be sure to face the band as shown in the parts diagram. Mount it “standing up”, using care to ensure proper polarity.
QT1 PARTS LAYOUT DIAGRAM 21. Install R1, 10K ohm (brown-black-orange). Notice again that this part is “standing up”. 22. Identify VR1, the 78L05 voltage regulator (marked 7805). This device produces a stable 5 volt reference for the circuit. Notice that this component has a “flat” side with the writing imprinted on it. Be sure to place the part as shown in the parts diagram. 23. Install C4, 1uF electrolytic. Watch that polarity! 24. Install C3, the last 1 uF electrolytic.
25. Install a short length of red hookup wire to the +V connection. 26. Install a short length of black hookup wire to the -V connection. CONGRATULATIONS You have just completed your QT1 Sub Audible Tone Encoder/Decoder. Take a well deserved break now. Give your eyes a rest. When you return, be sure to check over your work on the entire circuit board. Energizing the circuit board with solder “bridges” or misplaced components can damage your kit.
QT1 TONE FREQUENCY PROGRAMMING Finally, it’s time to set the tone frequency on the Ramsey Quick Tone. The following chart describes the combinations of jumpers for the various tone frequencies. An ‘0’ indicates that a jumper block is not present, while an ‘X’ indicates that there is a jumper across the pins. 0 = No Jumper X = Install Jumper TONE FREQ (Hz) P5 P4 P3 P2 P1 P0 67.0 0 0 0 0 0 0 69.3 0 0 0 X X 0 71.9 X 0 0 0 0 0 74.4 0 0 0 0 0 X 77.0 X X 0 0 0 0 79.
Select and program the desired tone frequency (e.g. 100.0 Hz = 01101 = Jumper installed in P5, P4, and P1). Connect the unit to a suitable power source (5 - 15VDC). Connect the PTT line to circuit ground while observing the the “OUT” connection. You should be able to detect the tone output (using an oscilloscope) and vary its amplitude using R7. Disconnect the PTT line; ground the ‘OTL’ (Open To Listen) pin, and connect an audio signal generator (or equivalent) to the ‘RX IN’ audio input pin.
(or tie to ground) Hook-up #2: Tone Encode and Receive Decode This hook-up allows muting of the receive audio until the proper tone is being received. The open collector “RX MUTE” is tied to the high side of the volume control pot. Following are a few “pro’s and con’s” concerning this type of configuration. 1. This interconnection requires no disabling of the original audio path inside the receiver to function. You can even hook-up the unit with ‘clip’ leads to check its functioning. 2.
The next diagram shows a more involved way of interfacing your kit. This configuration more fully utilizes the MX-COM. IC and its more advanced features. 1. This connection used the “built in” audio filtering provided by the MXCOM. chip for superior audio quality, both on receive and transmit. 2. In this configuration you may also trip the mic hanger in transmit mode to eliminate any unwanted “squelch tail” that is present. 3.
opinions, comments, and additions that you would like to see in future publications. Please submit comments or ideas to: Ramsey Electronics Inc. Attn.
Quick Reference Tone Sheet Frequency 146.880 Offset (+/-) Tone Freq Preload + 100 Hz 01101 RAMSEY KITS ...
The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
Ramsey Quick Tone CTCSS TONE ENCODER DECODER Quick Reference Page Guide Introduction to the QT1 ............................. 4 How it works .............................................. 4 Schematic diagram ................................. 10 Parts list .................................................... 6 QT1 Assembly instructions ....................... 7 Parts Layout diagram .............................. 11 Hook-up configurations ............................12 Troubleshooting ........................
