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 exceptional synthesized transmission range and improved audio quality that puts your favorite radio station to shame. • great for transmitting your tape deck or ...
Fm25a • 2 partial list of available kits ramsey transmitter kits • fm25, mp3fm fm stereo transmitters • am1 am transmitter • tv6 television transmitter • fm100 professional fm stereo transmitter ramsey receiver kits • fr1 fm broadcast receiver • ar1 aircraft band receiver • sr2 shortwave receiver • ...
Fm25a • 3 synthesized fm stereo transmitter kit ramsey publication no. Mfm25a price $5.00 table of contents introduction ...................................... 4 circuit description ............................ 5 parts layout diagram ...................... 7 fm25a parts list ...........................
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 the rules of your nation’s telecommunications authority. For u.S. Residents, that authority is the federal communications commission (fcc). The fm25a...
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, the dc isn’t ‘proper’ enough to provide us with the low-noise, stable supply that we would like for good audio quality. Voltage regulator vr3 provides ...
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 completely sent is less than 1/100th of a second! U1 is a phase locked loop (pll) synthesizer ic. It takes the 6 mhz crystal fre- quency and divides it ...
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,c28,c29,c31] 7 .01 µf disc capacitors (marked .01 or 103 or 10 nf) [c7,c8,c15,c23, c24,c42,c43] 2 .1 µf disc capacitor (marked .1 or 104 or 100 nf) [c9,c16] 2 .022...
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 leads), taped to paper. [y2] 1 78l05 +5 volt voltage regulator [vr1] 1 78l02 +2.6 volt voltage regulator [vr2] 1 7812 +12 volt voltage regulator [vr3] 1 68hc705k1 ...
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 to this kit than just soldering a few parts. So that you don't spend extra time "troubleshooting" instead of getting on the air, we strongly recommend that you f...
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 over the edge of the printed circuit board. Solder all six pins. 2. Install s2, the small black mini push-button switch. Solder all 4 or 2 pins depending...
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, insert the parts groupings as one operation, then solder and nip all connections. Most of the resistors will be installed in a stand up fashion. That is, on...
Fm25a • 13 power supply 1b. Install c5, the large 470 - 1000 µf electrolytic capacitor. Be sure to po- sition for correct polarity. 2b. Install vr3, the 7812 12 volt regulator. Make sure the metal tab is ori- ented as shown in the parts layout. The text side of the component should be facing s1. 3b....
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 essential to the fre- quency stability of your transmitter. 16c. Install r8, 47k ohms (yellow-violet-orange). 17c. Install c16, .1 µf disc capacitor (marked...
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. 9d. Install r18, 10k ohms (brown-black-orange). 10d. Install r14, 220 ohms (red-red-brown). 11d. Install c23, .01 µf (marked .01 or 103 or 10 nf). Rf low...
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 capacitor (marked 103 or .01 or 10 nf). 18f. Install r1, 10k ohms (brown-black-orange). 19f. Install q1, the transistor marked 2n3904. The flat side must be pla...
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 fm portable radio closest at hand. It is your responsibility to carefully research what fm stations can be listened to with a good system within the transmitting...
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 frequency. No audio input is needed to make this first adjustment, you can simply listen for a "quieting" in the normal background noise "hiss." remember that...
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 that whatever is playing on the main system can also be tuned-in on portable fm radios in other rooms, the garage or in the yard. This connection cons...
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 audio mixers and processor. Mixers allow you to smoothly ‘blend’ from one audio source to another just like the commercial sta- tions do. Our stc1, st...
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 look at radio shack book no. 62-1083 on antennas. Our new tm-100 tru-match fm an- tenna is an ideal mate to your transmitter. It features proper imped...
Fm25a • 22 appendix a: fcc rules and information the rules of the fcc (federal communications commission)and your kit built fm stereo transmitter. An interim explanation of applicable fcc regulations supplied as a personal assistance to fm25a builders, by dan f. Onley (k4zra) it is the policy of ram...
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 rules and should not be construed to be the absolute complete legal interpretation! It is up to you to operate within the proper fcc rules and ramsey electronics, inc...
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 ordinary fm radio. • b. Fcc rule 15.215(a) says: "unless otherwise stated, there are no restric- tions as to the types of operations permitted under these sectio...
Fm25a • 25 chart to show the maximum permitted performance of a non-licensed fm band transmitter. The theoretical figures assume a simple 1 meter receiving antenna in all cases and do not take into consideration that reception can be greatly en- hanced with larger, multi-element antennas and preampl...
Fm25a • 26 there are three reasons to translate our look at "field strength" into "acres". 1. The first one is easy: the numbers would get too cumbersome if we dis- cussed your possible signal coverage in terms of square feet or square me- ters. 2. It's very easy to see that your signal can easily a...
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 spectrum. Lawful use suggestions 1. Build and adjust this kit strictly according to the published instructions. 2. Use the whip antenna supplied with the...
Fm25a • 28 notice: the radio-frequency "intentional radiator" device which may be constructed from kit parts supplied by us is intended and designed by ramsey electronics, inc. To conform to applicable provisions of part 15 of fcc rules. The individual kit-builder and all users of this device assume...
Fm25a • 29 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 assemble...
Fm25a • 30 price: $5.00 ramsey publication no. Mfm25a assembly and instruction manual for: ramsey model no. Fm25a required tools • soldering iron ramsey #rts06, (radio shack #rs64-2072) • thin rosin core solder ramsey #rts12, (rs64-025) • needle nose pliers ramsey #rts05, (rs64-1844) • small diagona...
