AM BROADCAST TRANSMITTER KIT Ramsey Electronics Model No.
PARTIAL LIST OF AVAILABLE KITS RAMSEY TRANSMITTER KITS • FM10A FM Stereo Transmitter • MP3FM Synthesized MP3 Transmitter • FM25B, FM100B Synthesized FM Stereo Transmitters • AM25 Synthesized AM Transmitter • AM1 AM Transmitter RAMSEY RECEIVER KITS • FR1 FM Broadcast Receiver • AR1 Aircraft Band Receiver • AA7 Active Antenna • SC1 Shortwave Converter RAMSEY HOBBY KITS • SG7 Personal Speed Radar • SS70 Speech Scrambler • TT1 Telephone Recorder • SP1 Speakerphone • MD3 Microwave Motion Detector • PH10 Peak hol
Ramsey Publication No. MAM1 Manual Price Only $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR AM BROADCAST TRANSMITTER AM1 TABLE OF CONTENTS Introduction to the AM1 ................. 4 AM1 Circuit Description ................ 4 Schematic Diagram....................... 6 Parts Layout Diagram ................... 7 Parts List ........................................ 8 Assembly Instructions ................... 9 Antenna Considerations............... 13 Alignment Procedures..................
INTRODUCTION Many times we wish to be heard via wireless communications. Whether transmitting music or voice, what’s required is a stable transmitter tunable to an unused frequency on the broadcast band. Here at Ramsey, we have produced several models of FM wireless units for years. Recent requests for an AM type transmitter have been answered with this kit.
Low Freq uenc y Audio Wa ve form High Freq ue ncy Radio Carrier Amplitude Mod ulated Signal output for the RF carrier frequency. The audio input path is routed from J1, the audio input source, to transistor Q2 to amplify the incoming signal. Notice that the transistor is biased to be linear using resistors R3, R5, and R6. The incoming audio signal is therefore amplified undistorted (for great sounding audio).
AM1 • 6
PARTS LAYOUT DIAGRAM AM1 • 7
PARTS LIST Please verify that the following items are in your kit before beginning assembly. RESISTORS 4 2 1 4 1 270 ohm [red-violet-brown] (R6,7,9,11) 1K ohm [brown-black-red] (R5,10) 2.2K ohm [red-red-red] (R1) 10K ohm [brown-black-orange] (R2,3,4,8) 5K PC mount potentiometer [marked 502] (R12) CAPACITORS 1 1 1 4 7 3 1 220 pF disc capacitor [marked 220 or 221] (see text C9,10,16) 470 pF disc capacitor [marked 470] (see text C9,10,16) .001 µF disc capacitor [marked .
ASSEMBLY INSTRUCTIONS There are numerous solder connections on the AM1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your transmitter! • • • • 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.
5. Solder all connections unless directed otherwise. Use enough heat and solder flow for clean, shiny, completed connections. 6. Trim or nip all excess wires extending beyond each solder connection, taking care that wire trimmings do not become lodged in PC-board solder connections. Now, let's get building! Since you may appreciate some “warm-up” soldering practice as well as a chance to put some “landmarks” on the PC board, we’ll first install some “hardware” components.
11. Install Q5, a 2N3904 transistor. Be sure to orient it correctly! See the parts diagram for correct orientation. 12. Install C7, .01 µF disc capacitor [marked .01 or 103 or 10nF]. 13. Install R9, 270 ohm [red-violet-brown]. 14. Install C15, 220 µF electrolytic capacitor. Electrolytic capacitors are polarized with a (+) and a (-) lead and must be installed in the correct orientation.
27. Install C3, .01 µF disc capacitor. 28. Install Q1, 2N3904 NPN transistor. Be sure to orient the part correctly. You’ve just completed the audio input circuitry. Have another look at your solder connections to ensure that there are no cold or intermittent joints. Hang in there, only 7 parts to go! 29. Install L1, the large 48 µH wire wound inductor. 30. Install R10, 1K ohm resistor [brown-black-red]. 31. Install Q3 and Q4, the last two 2N3904 NPN transistors.
Transmitter Frequency (KHz) C9 (pF) C10 (pF) C16 (pF) 1000 (marked .001 or 102) 2000/2200 (marked .002/.0022) 2000/2200 (marked .002/.0022) 550 - 720 2000/2200 (marked .002/.0022) 2000/2200 (marked .002/.0022) Not used 700 - 870 1000 (marked .001 or 102) 2000/2200 (marked .002/.0022) Not used 800 - 1000 470 (marked 470) 2000/2200 (marked .002/.0022) Not used 1000 - 1250 470 (marked 470) 1000 (marked .001 or 102) Not used 1250 - 1600 220 (marked 220) 1000 (marked .
Once the tuning capacitors and some sort of antenna have been installed, it’s time to align your transmitter. ALIGNMENT PROCEDURES Keep all tests very brief until you have carefully chosen an open operating frequency in the AM broadcast band. 1. Tune an AM receiver to a quiet spot on the dial where you wish to receive your transmitter. 2. Connect an antenna to the RF OUT jack. 3. Energize the circuit with a suitable power source. 4.
TROUBLESHOOTING INSTRUCTIONS While we had hoped that it wouldn’t come to this, if you are having trouble with your transmitter, here are a few suggestions. By far the most common sources of problems are misplaced parts or poor solder connections. It’s always best to take a break before searching for bad connections.
PLEASE READ THIS IMPORTANT FCC INFORMATION The AM1 is classified by the FCC as an “intentional radiator,” and it’s operation is covered by Part 15 of the FCC rules which were updated in June 1989. In brief, what you need to know about these rules is that your AM broadcaster must not interfere with AM radio or TV reception of other people. As designed, the AM1 complies with FCC technical requirements for devices used in the AM broadcast band.
“On the Air” Etiquette 1. Do not use “made up” call signs to identify your transmissions. Only the FCC has the authority to grant such callsigns. Use some other way to identify your transmitting activity, such as “ This is radio 550, Pittsford School Student Radio,” and so forth. 2. Identify the location and purpose of your transmissions from time to time. This is a common courtesy toward other persons who may hear your transmission.
8 ' WHIP Paper TubeTU PAPER To Transmitter TO TRANSMIT wind consecutive “loops” around the tube. For a frequency of 1000 KHz (or 1 MHz) you’ll need to wind 190 turns of wire around the tube for the proper inductance! Connect an 8 foot whip antenna to one end of the coil and the other end to the center pin of the antenna output jack. Experiment with different designs to determine which antenna type works best for you.
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.
AM1 AM BROADCAST TRANSMITTER Quick Reference Page Guide AM1 Circuit Description ................. 4 Schematic Diagram ....................... 6 Parts Layout Diagram .................... 7 Parts List .........................................8 Assembly Instructions .................... 9 Antenna Considerations ...............13 Alignment Procedures ..................14 Experimental Broadcasting ...........14 FCC Information ...........................16 Antenna Experimenting ................
