Ramsey Electronics FM25A Instruction Manual Page 1

FM25A • 1 Ramsey Electronics Model No. FM25A Own and operate your own FM Stereo broadcast station. Definitely not a toy, the FM-25A has an

FM25A • 10 RAMSEY "LEARN-AS-YOU-BUILD" ASSEMBLY STRATEGY As you can see in examining the circuit board and components, there is a bit more

FM25A • 11  1. Install S1, the DPDT horizontal push-button switch. It fits correctly only one way. Ensure that the white plastic switch extends out

FM25A • 12 Audio Input Circuits We encourage you to refer to the schematic diagram and learn the functions of the following parts. If you wish, inser

FM25A • 13 Power Supply  1b. Install C5, the large 470 - 1000 µF electrolytic capacitor. Be sure to po-sition for correct polarity.  2b. Install VR

FM25A • 14 and insert back into the can. Make sure L1 is squarely against the top of the PC board before soldering. Solid installation of L1 is essen

FM25A • 15  8d. Install Q2, the other transistor marked C2498 (or 2570). Again watch the placement of the flat side and mount as flush as possible.

FM25A • 16  16f. Install R31, a 1K ohm resistor (brown-black-red). Notice this resistor is a laydown component.  17f. Install C8, .01 µF disc capac

FM25A • 17 CHOOSING AN OPERATING FREQUENCY (A) It really is NOT sufficient to just "check" the FM band for an empty fre-quency, using the

FM25A • 18 After setting your DIP switches, recheck your ‘math’, depress the Program but-ton and listen on a nearby FM radio for the carrier frequenc

FM25A • 19 USING THE FM25A WITHIN THE HOME A most practical use for the FM25A would be to connect it to the main stereo system within a large home so

FM25A • 2 PARTIAL LIST OF AVAILABLE KITS RAMSEY TRANSMITTER KITS • FM25, MP3FM FM Stereo Transmitters • AM1 AM Transmitter

FM25A • 20 RAMSEY’S HAS MIXER (MX) KITS! You can greatly add to the versatility and professionalism of your transmitting station by adding one of our

FM25A • 21 Ham radio books and magazines are filled with antenna principles and ideas which can be adapted to your application. Also, you may wish to

FM25A • 22 APPENDIX A: FCC RULES AND INFORMATION The Rules of the FCC (Federal Communications Commission)and your kit built FM Stereo Transmitter. An

FM25A • 23 Here are the primary "dos and don'ts" picked from the current FCC Rules, as of May, 1990. This is only a brief look at the

FM25A • 24 kit operates well within this limit. In fact, its signal should sound no "wider" than any other FM station when listening on an

FM25A • 25 chart to show the maximum permitted performance of a non-licensed FM band transmitter. The theoretical figures assume a simple 1 meter rec

FM25A • 26 There are three reasons to translate our look at "field strength" into "acres". 1. The first one is easy: the numbers

FM25A • 27 to accomplish any objective which the FCC sees to be in the public interest and not interfering with other authorized uses of the radio sp

FM25A • 28 NOTICE: The radio-frequency "intentional radiator" device which may be constructed from kit parts supplied by us is intended and

FM25A • 29 The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting

FM25A • 3 SYNTHESIZED FM STEREO TRANSMITTER KIT Ramsey Publication No. MFM25A Price $5.00 TABLE OF CONTENTS Introduction ...

FM25A • 30 Price: $5.00 Ramsey Publication No. MFM25A Assembly and Instruction manual for: RAMSEY MODEL NO. FM25A REQUIRED TOOLS • Soldering Iron Ram

FM25A • 4 INTRODUCTION The Ramsey FM25A is a true SYNTHESIZED STEREO FM broadcast transmit-ter, which any person may build and use in accordance with

FM25A • 5 CIRCUIT DESCRIPTION We will begin by talking about the power supply of your new FM25A. While a DC power source is provided with the FM25A,

FM25A • 6 may think that all this would take a long time but in fact the whole process from the time you press the program switch until the data is c

FM25A • 7 FM25A PARTS LAYOUT DIAGRAM

FM25A • 8 PARTS SUPPLIED WITH FM25A TRANSMITTER KIT Capacitors  8 .001 µF disc capacitors (marked .001, 102 or 1nF) [C10,C12,C13,C26, C27,

FM25A • 9 Hardware, Misc.  1 6 MHz crystal (thin shiny rectangle marked 6.00) [Y1]  1 38 KHz crystal (small silver cylinder with two small