Low Power Broadcasting FAQ (Frequently Asked Questions) contents: [1] What equipment do I need to start a station? [2] Is low power broadcasting legal? [3] How much power do I need? [4] Where can I get a transmitter? [5] What kind of antenna should I use? [6] How do I select a frequency? [7] Where can I get more information? ---------------------------------------------------------------------- [1] What equipment do I need to start a station? You will need audio sources (tape players, CD players, microphones, etc.), an audio mixer, a transmitter, a coaxial cable (usually RG-8 or RG-58/U) to carry the signal from your transmitter to your antenna, and an antenna. When you are selecting audio equipment, try to get items that have metal cases (not plastic or wood) and three-prong grounded electrical plugs. This will reduce your chances of having problems with radio energy from your transmitter getting into your audio gear and causing interference. The most important item for a low power broadcaster is the _raison_d'etre_, the reason for existing. You won't have a high power signal, and you won't have billboards and TV commercials announcing the existence of your station, so listeners will have to put some effort into finding and receiving your signal. They probably won't make the effort unless you are offering something unique and interesting. ------------------------------ [2] Is low power broadcasting legal? This depends on what country you are in. Here in the United States, legal unlicensed broadcasting is limited to microscopic power levels (see the Part 15 Rules FAQ in alt.radio.pirate for details). For example, the limit for unlicensed FM transmissionss is 250 microvolts per meter, measured at a distance of 3 meters from the transmitting antenna; at this power level, stereo reception with a good signal to noise ratio is only possible within a 100 foot radius, and an average car radio can barely detect the signal at a distance of 200 meters. Some people hope the increasing number of illegal "pirate" broadcasts will pressure the government into liberalizing the rules. Violators who get caught are usually given a monetary fine, and sometimes their equipment is confiscated. ------------------------------ [3] How much power do I need? There is no simple answer to this question. For starters, it depends on whether you are broadcasting on the AM (medium wave) band, the FM band, the international shortwave bands, or TV. In order to reduce interference to other radio services, it is always a good idea to use the lowest amount of power that will serve your target audience. On FM and TV frequencies, raising your antenna height and improving the gain of your antenna system is generally a better way to increase your range than using a more powerful transmitter. If an FM or TV broadcast antenna is only 12 feet (4 meters) above the ground, for example if it's in the attic of a one-story building, then its range will always be limited to a few kilometers and the signal will always be plagued by multipath interference, even if you pump a million watts into it. ------------------------------ [4] Where can I get a transmitter? Below is a brief list of companies selling low power transmitter kits. Please send me information about any companies not listed, so that I can include them in future versions of this list. Note to newcomers: to assemble these kits, you must be able to solder components onto a circuit board, and it helps if you know the difference between a resistor and a capacitor. If you haven't reached this stage of electronic know-how yet, consider buying some of the educational kits available from C&S Sales, 1245 Rosewood, Deerfield IL 60015, telephone 800-292-7711. Their electronic components course (item #ECK-10, $14.95) might be especially helpful to newbies. When assembling radio circuit kits, I prefer to use narrow-diameter silver-bearing solder (Radio Shack #64-013) and a 15 watt soldering iron (64-2051). You will need a more powerful soldering tool for making antennas out of large-diameter wire, soldering really large connectors to a printed circuit board, etc., but the 15 watt iron works fine for assembling most kits and reduces the chances of over-heating transistors and other heat-sensitive components. ----- DC Electronics P O Box 3203 Scottsdale AZ 85271 phone 800-423-0070 The Improved Stereocaster is an FM stereo transmitter based on the BA1404 chip with a few milliwatts of output power ($29.95 plus $3.50 S&H). It has a smooth fine-tuning control which makes it easy to get on the exact frequency you want, and a voltage regulator for the BA1404 which improves stability. Documentation is not quite as lucid as Ramsey's. ----- Free Radio Berkeley 1442 A Walnut St., #406 Berkeley, CA 94709 phone 510-464-3041 / 800-549-0732 Items listed in their advertisements include a 5 watt mono FM transmitter kit ($55 plus shipping), a 1/2 to 1 watt stereo FM transmitter kit ($50), an FM transmitter with phase locked loop (PLL) frequency control ($95), plus kits for output filters, dummy loads, RF amplifiers, and antennas. FRB is spear-heading a movement to challenge the FCC's regulations and is trying to foster a low power broadcasting movement. Contact them for more info. (Internet: frbspd@crl.com) ----- North Country Radio PO Box 53, Wykagyl Station New Rochelle NY 10804-0053 phone 914-235-6611 (send $1 for catalog) Many TV-related items: a 50 milliwatt UHF transmitter with crystal controlled frequency ($78); a "video pallete" to create special effects; a switcher that does cross-fades and wipes; and upconverters that will take channel 3 video from a VCR and shift its frequency up to any UHF channel 25 thru 70. For licensed radio amateurs, they have a line of more powerful UHF TV transmitters. With a 100-foot range and a price tag of $62.50, their FM stereo transmitter is not exactly competitive, but it is interesting from a technical point of view. Their stereo infrared transmitter and receiver could be used to build a difficult-to-trace studio-to-transmitter link. ----- Panaxis Productions P O Box 130 Paradise CA 95967-0130 (send $1 for catalog, or $2 if you're in a hurry) This company offers many interesting books and kits. The REB-1 kit is a 100 milliwatt transmitter for the upper end of the AM band ($34.95 plus shipping). The FMO kit ($75) is a high fidelity stereo FM transmitter kit with 2 to 20 milliwatts of output power. The FME-500, a half-watt mono FM transmitter with excellent technical characteristics, can be combined with their stereo generator to build a high-quality low power station (> $200 for the two kits). Panaxis kits might not be suitable for absolute beginners; you should have some experience in circuit assembly before you tackle these. ----- Progressive Concepts 1434 N. Mills Ave. Claremont CA 91711 RF amplifiers, FM transmitters and stereo generators, components for RF circuits and more. ----- Ramsey Electronics 793 Canning Pkwy Victor NY 14564 phone 716-924-4560 The FM-10A is an FM stereo transmitter kit ($34.95 plus shipping) with a few milliwatts of output power; it is based on the BA1404 integrated circuit. Ramsey kits have well-written instruction manuals, and most of the circuit boards have lots of wide-open space which makes modifications easy. The company also has a good reputation for service. These factors make Ramsey kits a good choice for beginners, in my opinion. Their AM transmitter kit (item #AM-1, $29.95) and their TV transmitter kit (item #TV-6, $27.95) might also be of interest; however, there is much room for improvement in the design of these two circuits. (Robert Myers of Ramsey Electronics tells me they do intend to release an improved version of the AM-1 kit at some point in the future.) ----- Supercircuits 13552 Research Blvd Austin TX 78750 This company sells a low-power TV transmitter for channels 3 thru 6 which appears to be of high quality ($49.95 plus $4.50 S & H). For licensed radio amateurs, they also sell some ham TV transmitter kits with 1 to 2 watts peak output power that can be adapted for use on UHF channels 14 thru 19, and a linear amp for boosting the output of these transmitters. ----- Tentronix 3605 Broken Arrow Coeur d'Alene ID 83814 phone 208-664-2312 Another BA1404-based FM stereo transmitter kit ($24). ----- Xandi Electronics Box 25647 Tempe AZ 85285 phone 800-336-7389 / 602-894-0992 The XFS108 kit ($41.95) is an FM stereo transmitter, probably based on the BA1404. Their advertisements give no specifics. ----- In a message dated Nov 08 06:01:55 EST 1994, an22190@anon.penet.fi wrote: >There is a company called "Spectrum Communications" in Dochester England >that sells fm transmitters and associated gear. A transmitter tunable from >88-108Mhz (part CTX100V) with output of 0.5Watt is available for 135 pounds. >This unit is synthesised. ... The phone number is 0305-262250. ------------------------------ [5] What kind of antenna should I use? Antenna theory, design and construction is a very complex topic. If you really want to understand antennas, I recommend that you buy a copy of _The_ARRL_Antenna_Book_ (published by ARRL, 225 Main St., Newington CT 06111 USA). It is a large book and you might have to spend several weeks studying it before it all begins to make sense. Assuming you want to get on the air in a hurry, and then build a better antenna system later on, I will describe the quickest and simplest options available. The systems described here are all less than optimum, but they will get you on the air pronto. WARNING: There are several ways you can get killed or injured while putting up an antenna. Never get within 10 feet of a power line, and never mount an antenna where it could possibly fall onto a power line, or where a power line could fall onto the antenna. Avoid falling off of roofs and ladders. Permanent outdoor antennas must be provided with a ground rod so that lightning, if it happens to strike, will go into the ground instead of into your equipment and your body. For FM broadcasting, try Radio Shack's omni-directional FM antenna (catalog #15-2164, price $12.99). Don't forget the 75-to-300 ohm impedance matching transformer (#15-1140 or 15-1143). (A 50-to-300 ohm transformer would be better, but you won't find those at Radio Shack.) This antenna can be mounted on a typical TV antenna mast, or a chimney, or hidden in the attic. Best results will be obtained when it's outdoors, away from trees and other objects, and mounted several feet higher than the rooftops in your neighborhood. In AM broadcasting, a vertical section of TV antenna mast, 10 or 20 feet long/high, makes a decent antenna. The center conductor of the coaxial cable from your transmitter is connected to the bottom of this vertical mast; the base of the mast sits on an insulator which sits on the ground. If the vertical radiator is made of several sections of antenna mast, make sure the sections are electrically connected -- try screwing some self-tapping sheet metal screws into the joints. The outer conductor (shield) of the coaxial cable is connected to a set of "ground radials," which are pieces of copper wire radiating out from the base of the antenna like spokes from the hub of a wheel. (The radials are not connected to the vertical radiator.) The radials can be buried a few inches below the surface for a permanent installation. "Beware the lawnmower." For shortwave broadcasting, a horizontal dipole works well enough. Cut two pieces of un-insulated copper wire; the length of each piece will be 234 feet divided by your frequency in MHz. Example: for 7385 kHz, each element will be (234/7.385 =) 31.7 feet long, and you will need two trees or other support structures about 63 feet apart. Solder one element to the center conductor of your coaxial feedline, and solder the other element to the outer conductor (shield) of the co-ax. (Note: the solder joints cannot bear the weight of the cable; loop the cable once over an insulator and provide some "strain relief".) Make a little loop at the free end of one element, and tie a long piece of string to that loop. Tie a small, heavy object (such as a lead fishing weight) to the other end of the string. Throw the weight up into the branches of a tree so that it goes over a branch and comes back down to earth; then hoist up that half of your antenna. Repeat the process for the other element. I don't know what to recommend for TV broadcasting. Anyone having experience, please e-mail your suggestions to me. ------------------------------ [6] How do I select a frequency? Receivers with digital tuning will only lock onto signals that are on standard broadcast frequencies. In the US, AM stations are at 10 kHz intervals, ranging from 540, 550, 560 ... to 1600. (Some Travellers Information Stations are licensed on 530, 1610, and 1620. The channels 1610 through 1700 may soon be allocated to broadcast stations.) In some other countries, AM stations are spaced at 9 kHz intervals. FM stations are spaced at 0.2 MHz intervals, ranging from 88.1, 88.3 ... to 107.9 MHz. Do not use an out-of-band frequency; they are allocated to other services. (For example, the frequencies just below 88 MHz are used for TV broadcasts, and the frequencies just above 108 MHz are used for aircraft communication.) Make a survey of the band you are planning to use. Get some graph paper or notebook paper and make a list of all the channels. Listen during the day and at night, making a note of what station(s) you can hear on each channel. Use a good receiver with digital tuning and a decent antenna, not some cheap piece of junk clock-radio or dime-store pocket radio. Repeat this band-scanning process several times during the course of a couple of weeks. (If you really want to be thorough, get a list of all the licensed stations in a 150-mile radius. You can extract this data from the _Broadcasting_Yearbook_ [a trade publication] or the FCC database [available on computer disks from several vendors]). If you know any DXers (people who make a hobby of listening to distant and unusual signals), ask them for a copy of their "log." Now, sit down with your data and search for an appropriate channel. Don't start with any prejudices or pre-conceived notions: don't plunk your signal onto 99.9 MHz just because you think it's cute ("666" upside down) or onto 1000 kHz because you think it's an easy number to remember. Don't try to wedge your signal into the non-commercial part of the FM band (88 to 92 MHz) if there isn't an appropriate opening there. An appropriate channel for low power broadcasting is one that is not occupied by a local station, or by an often-audible* distant station. The adjacent channels -- the next channel above and the next channel below the one you're considering -- also must not be occupied by local stations, because they will "splatter" onto your signal (and they will claim that you are splattering onto them). There are a couple of other things you must keep in mind when selecting an FM broadcast frequency. First, if there is a TV station broadcasting on channel 6 in your area, it is unwise to operate on 88.1, 88.3, or 88.5 MHz. TV receivers have broadband tuning circuits (a TV channel is 6 MHz wide, enough spectrum to hold 30 FM stations), so broadcasts at the "low edge" of the FM band can easily interfere with reception of channel 6. In some areas where the authorities have foolishly licensed both a channel 6 and a low-edge FM station, the stations often have to go to great lengths to deal with interference complaints. Another thing for FMers to consider is the mixing of signals that can occur in a listener's receiver. Most FM radios use an intermediate frequency of 10.7 MHz; in other words, whatever frequency you're tuned to is converted down to 10.7 MHz before the sound waves are extracted from the radio waves. As a result, a strong signal can interfere with reception of stations that are on a frequency 10.6 or 10.8 MHz above or below it. For example, if you transmit on 92.3 MHz, some listeners who are located near your transmitter will have trouble hearing a station on 102.9 or 103.1 MHz (92.3 + 10.7 = 103.0). The interference might take the form of an "image" of your signal being heard on the other frequency, or vice versa; or a mixture of the two signals might be heard on blank spots and on top of weak signals all over the band. Any other transmitter in your immediate neighborhood, whether it's a cellular telephone system, an AM or FM broadcaster, or any other service, might interact with your transmitter in unexpected, interference- causing ways. So, do some testing with a variety of receivers (including cheap junk) before you make a final decision on your frequency. In many major cities where the FM band is quite crowded, you will find a few conspicuous empty channels; in some cases, these channels have been kept unused (or had to be evacuated) because of interference problems caused by signals mixing together at the transmitters or in people's receivers. *How to define "often audible" is a matter of debate; opponents of radio freedom say that _every_ channel is occupied by a distant station that some DXer might be able to hear with his 50-foot antenna tower and $1,000 radio. ------------------------------ [7] Where can I get more information? Introductory electronics textbooks are available at most bookstores and libraries. Magazines such as Electronics Now, Popular Electronics, 73, QST, Communications Quarterly, and Nuts & Volts sometimes have articles and advertisements of interest to low power broadcasters. Monitoring Times and Popular Communications carry relevant news items from time to time. The ACE, a monthly newsletter, covers shortwave pirates well and occasionally contains data useful to AM and FM broadcasters (send $2 for a sample copy to Box 11201, Shawnee Mission KS 66207). Keep an eye on these Usenet newsgroups: alt.radio.pirate rec.radio.broadcasting rec.radio.amateur.antenna Files of some relevance are available for ftp from these sites: site directory filename ==== ========= ======== ftp.std.com /periodicals/lingua/harrison lowpower.faq(this text) part15.faq crl.com /users/ro/frbspd (several) dg-rtp.dg.com /fm10 FM10-FAQ(text after copyright) ---------------------------------------------------------------------- This text is copyright 1994 by Rick Harrison. Permission is hereby granted for unlimited distribution of this text via Usenet newsgroups, Internet file servers, and computer bulletin boards. Any publication of this text in semi-permanent form (such as hardcopy or CD-ROM) requires the author's prior permission. RAMSEY FM-10 INFO V10.2 Contents: * 1) About the Author * 2) DISCLAIMER! * 3) About This File * 4) FM-10 Mailing List * 5) FM-10 Archives * 6) Snail Mail Info Packet (or FM Micro Power Radio Guide) * 7) Other Places to Look in Cyberspace * 8) Other FTP Sites * 9) ARRL * 10) Radio Resistors Bulliten * 11) Recommended Test Equipment * 12) Dummy load * 13) RF Probe * 14) Paranoid? * 15) Ramsey's Address * 16) Ramsey FM-10 70mw output amplifier * 17) Ramsey PA-1 2-meter to 3-meter conversion mod * 18) ANTENNAS -- read, read, read, read, most important! * 19) On The Road * 20) Filter design for FM Radio Transmitters * 21) FM-10 Myths * 22) FM-10 Improvements * 22.1) Stereo Pilot Mod * 22.2) Crystal Mod * * 22.3) Treble Boost Mod * * 22.4) Anti-Drift Mod 1 * 22.5) Anti-Drift Mod 2 * 22.6) Power Filter Mod * 23) Component/Kit Sources * 23.1) BA1404s and other FM Broadcaster * 23.2) 38KHz Crystals * 23.3) FM KITS FROM FREE RADIO BERKELEY * 23.4) The makers of the infamous BA1404 * 24) Other Raw Info _________________________________________________________________ 1) ABOUT THE AUTHOR Author : Mycal E-mail : mycal@netacsys.com WWW: ftp://netacsys.com/pub/web/mycal/mycal.html Edition: 10.2 Latest version from ftp://netacsys.com/pub/web/mycal/fmfaq.html This file is Copyright (C) 1993, 1994 by Mycal I grant free copying rights via BBS's, USENET, Internet FTP sites. Distribution via printed media or CDROM requires the author's prior permission. Once more If you have any info, I stress **ANY*** about this subject please drop me a byte or two. Have fun, mycal@netacsys.com _________________________________________________________________ 2) DISCLAIMER! Here is a rough compilation of information about the Ramsey FM-10, and other BA1404 Stereo FM broadcasters. Some of the modifications may make your BA1404 based broadcaster illegal to use on the open airwaves in the US and Canada. Also it has been brought up that the stock Ramsey FM-10 kit may exceed FCC power limits when used with a proper antenna. The information contained in the file is in no way complete, nor do I take any responsibility for its accuracy. With that in mind, along with the above paragraph I must say: THIS FILE FOR INFORMATIONAL PURPOSES ONLY THIS FILE FOR INFORMATIONAL PURPOSES ONLY _________________________________________________________________ 3) ABOUT THIS FILE When I first started hacking on my FM-10, a few of us on alt.radio.pirate were exchanging information on mods to improve the range, stability and audio quality of the FM-10. After a couple of posts about filters and amps, my mailbox was swamped with requests for copies of previously posted information and other questions about the FM-10. So rather than drive myself crazy with sending a piece of info here and there, I decided to dig through my mailbox an notes and compile this file. I hope it helps. Also if anyone has more information about the FM-10 or FM transmitters, antennas, mixing equipment, programming information, stories about pirates, or anything else that falls into this realm, please send it to mycal@netacsys.com. I will try to update this file as new information becomes available. Also I am working on a some Postscript files that will contain instructions on how to build some equipment that is to complex for ASCII art. You might want to check the FTPable archives every month or so. I would like to say thanx to all the people that contributed to the information in this file. The list has grown quite long, and some of the contributors would like to remain anonymous. So for now I am going to forgo all the names, if this is not up to your liking please let me know. _________________________________________________________________ 4) FM-10 MAILING LIST (down?!) _________________________________________________________________ 5) FM-10 ARCHIVES Yes it is finally here, message archives of the FM10 mailing list and a place to put/find schematic, reviews, stories, etc. related to the FM-10 and other BA1404 based FM transmitters. Currently a 350mw amp plan, 800mw amp plans, "Radio is my bomb" text, slim jim plans/info and the BA1404 spec sheet are located there. People can FTP into dg-rtp.dg.com with user "anonymous" and password "". In the fm10 directory you'll currently find three sub-directories and a file: * archive/ This directory contains: + amps/ - 800mw.zip, amp_5-40W, fixed.ps.Z, mycal350.ps.Z, and mycal350.zoo + antennas/ - jpole antenna kit (software and documents), 3-meter Slim-Jim plans + ba1404-specs/ - TIFF files with official specs + CPP-Holland/ - Projects (amps, PLL-circuits, Stereo coders, SWR-meter, etc) + misc/ - min-radio-station kit, stories/news-clips, projetcs, etc. * incoming/ - This is writable by everyone and this is where people should upload new stuff. * msg-archives/ - This directory will have files named according to the date they were last "sealed". The file "Current" is a running log of all EMail messages from the last "seal" date of the archives. * "FM10-FAQ" - older version of this FAQ _________________________________________________________________ 6) SNAIL MAIL INFO PACKET (OR FM MICRO POWER RADIO GUIDE) The info packet has evolved yet again, it is now 50 pages. It includes plans for 4 amps, a 200mw, 350mw, 800mw, and 5watt. Instructions for modifying the Ramsey PA-1 for FM broadcast band operation. A section on how to design and build your own antenna. Plans for a power meter, regulated power supply, and dummy load. A block diagram showing a typical station. Spec sheet for the BA1404. FM-10 modifications. Sources for parts and info. And a more up to date design of my digitally synthesized transmitter. Loaded with schematics, board-layouts and diagrams. Plus, schematics and construction details of the FRB 5 watt transmitter. And now compressor and limitor plans, FCC facts and reality, DIY media article. The price for this packet is $10 in the US and $12 overseas. Address to send the $$ to is: mycal PO Box 750381 Petaluma, CA 94975-0381 You can also use this address to send me any info that would be hard to send by email. I will trade info packets for hard copy information, email me for details. Note: this packet is in a constant state of change, more info could be added at any time. _________________________________________________________________ 7) OTHER PLACES TO LOOK IN CYBERSPACE alt.radio.pirate is another good forum to find or post information on FM radio transmitter. Although you may not have pirate aspirations, many of the things talked about can benefit everyone. Other places to scan, sci.electronics and the amateur radio groups. _________________________________________________________________ 8) OTHER FTP SITES Rick Harrison's FTP site containing a low power FAQ and a part 15 FAQ can be found by FTP'ing to site ftp.std.com and looking in the directory /periodicals/lingual/harrison Free Radio Berkeley now has an archive on CRL. It can be accessed by FTP'ing to site ftp.crl.com and looking in the directory /usrs/ro/frbspd _________________________________________________________________ 9) ARRL The American Radio Relay League (ARRL) has a useful service -- the ARRL Information Mail Server. This is an automated mail server that let's you access many of our information files, containing information about various facets of Amateur Radio. Some of the information has technical value that is related to all radio services. To use it, send a mail messages with the word: help in the body of the message to: info@arrl.org This will give you all the information you need to use this service. _________________________________________________________________ 10) RADIO RESISTORS BULLITEN A little zine that sometimes discusses pirate/micropower radio along with public radio stuph. Send frank a buck to help out with the copying and stamps. Very Good, and now available in Electronic form. E-mail Frank at haulgren@henson.cc.wwu.edu for details. Frank Haulgren RRB PO Box 3038 Bellingham, WA 98227-3038 _________________________________________________________________ 11) RECOMMENDED TEST EQUIPMENT * An SWR/Power meter is a giant help, a CB to 2 meter one will suffice. Power readings will not be accurate, but can be useful for peaking. The most important part is the SWR meter, this is very important when making an antenna. A NOTE on power meters. I recommeded the above power meters because they are inexpensive and most people that are interested in hacking a FM-10 have very limited funds. These are by no means accurate, but they will give you some idea what is going on. If you can spend the money you can get an accurate power meter that is designed for this band, but the cost is 10-15 times more. * A rf probe could also be used as a replacement for a powermeter, construction details below. * A 50ohm non inductive load is also very helpful, for low power applications a 50ohm 1/4 or 1/2 watt carbon resistor works well. This can be used to tune up your kit and amp without interfearing with anyone. Also note that you can run as much power you want, legally, as long is it doesn't radiate. * A VOM is also very helpful. High I would put out the extra bucks and buy one with a freq counter (if you shop around, about $60-$70). Buy the one that covers audio to 20MHz(or more). If you are serious about electronics you need one of these! _________________________________________________________________ 12) DUMMY LOAD Dummy loads are great for testing, without radiating a signal. In fact you can run as much power as you want into one of these things legally! Basically you want to create a non-inductive 50-ohm load. This can be done with regular carbon resistors, or by buying pre built Amateur or CB radio loads. For low power ( <.5 watt ) an ethernet terminator works well (check temp when using if it gets very hot lower input power, if it is still cool you may be able to go up to .75 watt) Most CB loads use a 2-watt carbon 50-ohm resistor. You can build your own, as wimpy or as studly as you want by running resistors in parallel to create 50-ohms. ie, 2 100 ohm 1/4 watt resistors will create a 1/2 watt 50 ohm load... Do not use 50 ohm wire wound resistors, they are not 50 ohms at radio frequencies. ----- ---------\ Sample Dummy Load where -****- = 50 ohm ---|--****-- / mounted in UHF connector. carbon --------- resistor ----- _________________________________________________________________ 13) RF PROBE For those of you (like me) who are in constant Starving Student mode, and DON'T have a good Scope, you can use a good DMM for RF power calculations. All you need to do is build a RF probe. Here's the schematic: (Yes, taken from 1989 ARRL Handbook) --probe tip-----||-+---/\/\/\-------to center of 50 ohm coax. .01uf | 4.7M +------to braid ___ | \_/ | --- diode | | | cliplead for gnd---+-------------+ Anyway, the diode should ideally be a Schottky diode (low rf capacitance). Although a 1n914 will work. To use, just hook up to your digital Meter, set on DC voltage. You will get very close to RMS RF Voltage. (this probe was specified for a 10Meg Ohm meter). To calculate power into a KNOWN purely resistive load (a.k.a. a dummy) use: e^2/R where e is the RMS RF voltage, R is resistance :-) This is also useful for checking inputs and outputs of low power RF units, since the inexpensive power meters don't seem to do real well below 1watt. _________________________________________________________________ 14) PARANOID? I've been talking to a few people that are worried about there "voice" being on the air, since they are afraid of being recognized. So I dusted off the old stacks of Radio-Electronics and found two articles that may be of intrest. In the January 1993 issue they have a "build your own digital voice changer" using a simple Real time digital signal processor. I think that this design is very simalar to the voice changing telephones. It basically raises or lowers your voice pitch. A place called LNS Technologies @ 1-800 -886-7150 sells the kits for $59. In there September 1992 issues they have a "build this dsp voice-effects board" using a little more complex, programmable, real time digital signal processor. The software they include contains a harmonizer, echo, reverb, and pitch. The kit is sold by American Disributors Inc for $105 @ 1-800-877-0510. You can also write your won software but the programmer is several hundred $$. DC electronics has a Robot Voice Kit for $15. I don't know how well this works or what it sounds like, but it clames to be adjustable for many different effects. _________________________________________________________________ 15) RAMSEY'S ADDRESS If your looking to purchase a FM-10 kit and can't find one locally try: Ramsey Electronics, Inc. 793 Canning Parkway Victor, New York 14564 Tel: 1-716-924-4560 Fax: 1-716-924-4555 _________________________________________________________________ 16) RAMSEY FM-10 70MW OUTPUT AMPLIFIER Provides almost 9db gain to bring the output power of the Ramsey FM-10 Stereo transmitter from 8mw to 70mw. Not the best design, but all parts can be found at Radio Shack! Much better designs are available at the archive site. If you want an updated, [a real schematic] [GET]. If you don't have graphics: +12v | / \ R1 *220 ohms(1/2 watt) / \ | === ** F2 | R2 9k | C2 +-/\/\/\/---+-------||-----> output | / ** F1 === C / | | / C1 | B |/ <----------MPS2222A (276-2009) in --||--+---|\ E -or- 2N4401 (better) ^ | -> -+ -or- MPS918 (best) | | | GND currently on board * you can also use 2 440 ohm 1/4 watt resistors run in parallel ** Optional but recommended, Ferrite beads, help prevent oscillation, and help the amplifier produce more gain. Slip over one end of the resistor. I built this thing right on the underside of the FM-10 kit, C1 is the cap that currently goes to the RCA ant jack, the 9k and the 220 ohm resistor have to be bought, note that if you cannot find 220 ohms you can make one by using 2 440 ohm resistors in parallel, and that a 10k will work in place of the 9k but yields poorer performance (-5%). The MPS2222A is from Radio Shack part number 276-2009, use this part! if you substitute it for a 2N2222A you will get only half the gain. Be very careful to get the leads in the correct orientation! I have found that a 2N4401 can be used in place of the MPS2222A with a little better performance, about 5mw more. I think the 2N4401 can be found at Radio Shack too. The MPS918 can produce up to 150mw. C2 is of the same value of C1, I took the one that goes to the on board antenna pad. Important! the value for R1 that seems to be optimal is 220 ohms, but it is very close to the sat point, If the amp. seems noisy (interferes with the TV etc.) back this value off to 240 ohms. If you lower this value below 205 ohms the power meter may read higher power but this will not be true, the transistor will be spewing all kinds of junk and the power meter will mistake this for higher output (in reality the signal we want will drop considerably) Well that's it, effective range with a good antenna should be a little over double. _________________________________________________________________ 17) RAMSEY PA-1 2-METER TO 3-METER CONVERSION MOD The Ramsey 2-meter amp (PA-1) can be converted for use on the FM broadcast band. The following changes need to be made: * L1 - should be replaced with a 1-turn 1/4" diameter coil, identical to the stock L2 shown in the PA-1 manual. * L2 - no change required * C1 - no change required * C2 - should be replaced with a larger trimmer capacitor. Use a trimmer that will go up to at least 125pF. * C3 - no change required. At higher power levels (>15 watts), this capacitor should be replaced with a trimmer that goes up to at least 200pF. * C4 - should be replaced with a larger trimmer capacitor. Use a trimmer that will go up to at least 125pF. Tuning: Tuning the amp for proper operation on 3-meters can be tricky. I suggest the following setup: FM xmitter -> SWR Meter -> PA-1 -> Power Meter -> 50 ohm dummy load Starting with C1 and C3 about 1/2 turn from closed, tune C2 and then C4 for maximum power output. If the SWR is much over 2:1, you will need to adjust C1, C2, and C4 to reduce it to an acceptable level. Watch the output power while you do this. Sometimes, tuning the trimmers for minimum SWR will peak the power output, whereas other times the power output will drop markedly. Avoid trimming the capacitors that have a large negative effect on the power output. After several iterations of adjustment, you should have decent power gain and low input SWR. Note: Watch for sudden jumps in power output that you can't linearly tune through. If you encounter this happening, chances are your SWR between the transmitter and amplifier will go way up, too. This is a sign that your amplifier is oscillating and you will need to tune it out of this region for proper operation. _________________________________________________________________ 18) ANTENNAS -- READ, READ, READ, READ, MOST IMPORTANT! Do you have a good antenna? I think that is the most important thing that you can do for extended range. I built a 1/4 wave ground plane using a UHF connector and 5 lengths of copper plated brazing rod (found at the local welding shop). Works great and only cost $3 dollars to make. Remember good antenna will improve you range much further than a good amp into a bad antenna. So this should be your 1st project to increase your range. use the formulas out of your FM-10 manual 234/freq=length of rod. Example: 234/88Mhz = 2.66 feet * 12 in/feet = 31.9" -or- 234/108Mhz= 2.17 feet * 12 in/feet = 26" insert the 4 ground plane rods in the 4 holes of the UHF connector, stick them through about 1/4 inch and solder. Solder the radiator in the top of the UHF connector (you may have to grind it a bit to fit.) Then bend the ground plane rods to a 45 degree angle to the radiator. There you have it a very effective antenna, just connect with a 50 ohm CB cable to your amplified Ramsey, stick the antenna in a tree or in another high place and you should have 1 miles of solid coverage (when using the above amp.). Also If you have an SWR meter you can cut the rods a little longer and start clipping the ends off a little until you get the best SWR reading. | | | | = brazing rod | | | | | ----- ----- ----- = UHF connector | - | / - \ - | | / \ | | / \ The final antenna should look like this: | ^ | | // \\ sky ground --horizon-- | v That is 1 radiator pointing strait up and 4 ground plane radials. (sorry for this extreme description, but there has been some confusion.) Be careful when you bend the brazing rod, don't break the connector. Grab the rod right below the connector with a pair of vice-grips (or the likes) and bend the brazing rod at that point. Try not to have anything metal near the radiator, this will effect the radiation pattern. The radiation pattern should look a lot like a doughnut surrounding the radiator, though deformed a bit. I have been told that you can shorten the radiator and make the ground radials longer to lower your radiation angle, but I haven't tried this, nor do I know what this would do to the antenna impedance. _________________________________________________________________ 19) ON THE ROAD Old magnet mount CB antennas can make great mobile antennas, just take all of the base load out of them and cut the radiator to 1/4 wave length. If you need a longer radiator than the one that comes with the antenna use the above mentioned brazing rod. I've tried this antenna and it works great! It is better than my di-pole at home and you can drive to a high, optimal location for your broadcasts. Also with this setup you need very little coax cable. Line loss using RU-58u can be killer @ 100MHz. You could also try a 5/8 wave length antenna, this would give you 2+db gain, or almost 2x power gain on transmit. _________________________________________________________________ 20) FILTER DESIGN FOR FM RADIO TRANSMITTERS It is very important to have a clean signal - the way 99% of all people who get busted for illegal transmitting is that the people that live around them complain about interference. Most of this interference is caused by harmonics. Filters cut down these nasties. So don't draw attention to yourself, keep everyone happy, including yourself, be clean, use a filter. When you amplify a signal, you get unwanted byproducts these are called harmonics. The show up at multiples of your starting frequency. For example if you amplify a 50MHz signal you may get echo's on 100MHz, 150MHz 200MHz, 250MHz... If you interfear with your neighbors TV, the local fire department, or anyone else, you are just asking for trouble. If you are only on the FM Band, you will hardly be noticed. Many FM transmitters are designed without adequate filtering on the output. Add to this the fact that most pirate radio operators lack spectrum analyzers with which to tune up their equipment, and it is easy to see that many stations are likely to be full of spurious outputs. You're a lot more likely to attract the attention of the FCC if you wind up interfering with all your neighbors television sets because of spurious emissions than you are if you emit a clean signal. While more elaborate 5- and 7-element filters offer greater attenuation of harmonics, I have found the following design to be simple and very useful. Furthermore, several of these filters may be chained together in series to produce even better filtering [**] If you make L1 with the 18 gauge wire as indicated and use capacitors rated at 50 volts, the power handling capability of this filter will be around 20 watts. If you use 100 volt capacitors, it should be able to handle 50 watts or more. The insertion loss of the filter is generally less than 1dB if you stay below the F(0db) point. Here is a [schematic] [GET] for a 3-element lowpass filter: input o---+---uuu---+---o output | L1 | C1- -C2 - - | | gnd o---+---------+---o gnd The following table summarizes 5 different variations of the 3-element lowpass filter. I have constructed and tested some of these myself and find that they work as advertised. The attenuation figures shown below were produced by spice. 3-element Lowpass with ~50 ohms input/output impedance ====================================================== C1 C2 L1 F(0db) F(3db) F(6db) F(10db) F(20db) --------------------------------------------------------------- 33pF 33pF Note1 113MHZ 138MHZ 163MHZ 200MHZ 320MHZ 39pF 39pF Note2 98MHZ 119MHZ 140MHZ 173MHZ 293MHZ 47pF 47pF Note2 95MHZ 112MHZ 130MHZ 160MHZ 270MHZ 52pF 52pF Note2 92MHZ 107MHZ 125MHZ 152MHZ 255MHZ 56pF 56pF Note2 90MHZ 105MHZ 121MHZ 147MHZ 246MHZ 62pF 62pF Note2 87MHZ 101MHZ 116MHZ 140MHZ 235MHZ Notes: 1. 2 turns #18 wire with a 5/16 inch inner diameter. Wind snugly at first. If SWR is objectionable, increase spacing between coils a little bit at a time. 2. 2 turns #18 wire with a 3/8 inch inner diameter. Wind snugly at first. If SWR is objectionable, increase spacing between coils a little bit at a time. I constructed my filter in a tiny aluminum enclosure with female chassis mount BNC connectors mounted for the input/output. I soldered C1 and C2 between the center connector and ground on each BNC connector and soldered L1 between the two center pins on the BNC connectors. [**] You can make a 5 element filter using the above parameters by using the following configuration: input o---+---uuu---+---uuu---+---o output | L1 | L2 | C1- -C2 - C3 - - - | | | gnd o---+---------+---------+---o gnd Were C1=C3, C2 = (C1 * 2), L1 = L2, and the C1, L1 values are taken from the above chart. [Also of interest is that the FM-10 puts out about 8-9mw and the 2nd harmonic is -25db off the fundamental (frequency we are broadcasting on). The FM-4 Kit by Ramsey puts out 130mw and the 2nd harmonic is only -12db off the fundamental, which means the 2nd harmonic of the FM-4 is about as powerful as the FM-10. db is log10, ie 3db is 2 times 6db is 4 times...] _________________________________________________________________ 21) FM-10 MYTHS There have been several myths about the FM-10 kit, the most prevalent are: 1. The FM-10 puts out 100mw of power. This is not true, or at least not true for the Ramsey FM-10's that I have tested. They put out about 8mw when driven with a 12volt supply. (Note: there has been several revisions of the FM-10, it is possible that the original version put out more power, but I find even that highly unlikely since it would require another amplifier stage.) Also the FM-10 is the only low cost kit, that I have seen, with an amplifier stage. Most others have power outputs in the fraction of a mw area. 2. The FM-10's output can be cranked up by reducing the value of R9. This like the above is not true. R9 and R10 are optimized for maximum output and greatest harmonic suppression at 12volts. There are much better ways of getting more output power than to mess with this output stage. Lowering the value of R9 will most likely degrade the FM-10's performance and cause lots of interference. _________________________________________________________________ 22) FM-10 IMPROVEMENTS Note : I sent this file and a list of other modifications to John Ramsey. Low and behold 4 monthes later the FM-10a is released. The new FM-10a incorporates the following mods marked with an '*'. _________________________________________________________________ 22.1) Stereo Pilot Mod One of the first problems experienced with the FM-10 is difficulty in getting the stereo pilot to operate correctly. One solution is to replace C7 and C8 with a 38KHz crystal, this works the best and is recommended. If you cannot find a 38KHz crystal, you can make your life a whole lot easier with a couple part changes. As indicated on the Ramsey schematic, about 110pF is necessary to tune the oscillator. The components supplied to achieve this are a small fixed value capacitor (C7) and a slightly larger value trimmer (C8). Since proper setting of the trimmer occurs within a very small 'window' (about 5% of the trimmers range), it can bet difficult or impossible to adjust the pilot to 19KHz and have it stay put. This can be cured by increasing the value of c7 to 100pF and replacing c8 with a 6-50pF trimmer (Radio Shack #272-1340); a 5-30pF trimmer will do the trick. The RS trimmer will not fit the holes in the pc board; one needs to cut the leads off a spare resistor and solder them to the legs of the trimmer (just use bits of wire) to mount it on the component side of the board. On a 2nd note: I replaced c7 with a 68pF cap and found it much easyer to tune a rock solid 19KHz at the test point. _________________________________________________________________ 22.2) Crystal Mod * Better than the above mod : old set up new setup c8 c1 xtl where c1=10pF and xtl=38KHz |-||-| |-||-|\|-| | c7 | | | v8=var cap |-||-| | | c7=cap | | | | Remove C7 and C8, replace with 38KHz crystal and 10pF cap. Note that the 10pF cap and the crystal are running series and the old cap setup is running in parallel. Note: If you have an FM-10 you can call Ramsey and get this mod for free! _________________________________________________________________ 22.3) Treble Boost Mod * Treble boost (pre-emphasis) improvement. The FM-10 appears to have been designed by someone outside the United States since it operates at the European audio standard of 50 microseconds. Receivers in the US are set up for 75 microsecond de-emphasis. R3 and R6 determine the time constant for the pre-emphasis curve. Replacing them with 75K ohm resistors (standard value 68K ohm is close enough) will result in improved audio response. A much better pre-emphasis/input circuit is shown in the July 1992 issue of "Radio Electronics". Not only do they use 75K ohm resisters in their pre-emphasis, but they filter stray RF signals by inserting a .001 cap between pin 1 (of the BA1404) and ground, and pin 18 and ground. It has been noted that the above mod may actually cause distortion on cheaper stereo receivers, since they were mass produced for the world market, they were designed for the European audio standard, which Japan and other Asian nations use too. Try it out, let me know what works for you. Note: the FM-10a kit comes with both sets of parts so you can select European or American audio standard. _________________________________________________________________ 22.4) Anti-Drift Mod 1 There has been quite a bit of discussion on the FM-10's frequency stability. Complaints that digital receivers cannot lock onto the FM-10's signal for any great length of time. I have used the below mod with good results (I used an NPO discs), but I have been told that Mylar or Polystyrene caps are even better. The FM-10 was designed to be inexpensive and cost-saving measures with components are inevitable. Disc ceramic capacitors are less expensive than silver-mica caps, and also much less stable. Simply replace c16 with a silver-mica, tantalum or negative temperature compensated disc cap of the same value. Even better is to cut the leads of the capacitor as short as possible and mount it directly on the bottom of the circut board. _________________________________________________________________ 22.5) Anti-Drift Mod 2 The FM-10 has two power grids, one is a low voltage grid to feed the BA1404. This low power grid uses three diodes to drop the input voltage to a safe level for the BA1404 which can only handle about 3.5 volts. Since the BA1404 contains the oscillator, and the frequency it oscillates on is dependant on the voltage that is feed to it, if you are feeding the FM10 with a non-regulated power source (ie a battery) you can make it much more stable by replaceing the three diodes with a zener type diode. Select a zener diode with a voltage value of 1.5 to 3. Remove the three diodes that are in series. Insert the zener diode with the banded end going to the low voltage + line and the other end going to the system ground. Even better is to use a voltage regulator like the 78L02 or 78L03, since zener diodes can be noisy. _________________________________________________________________ 22.6) Power Filter Mod Another flaw of the FM-10 is that they don't stop the RF from feeding back into the power supply. There are two 270 ohm resistors feeding the RF outputs, one R13 feeds the output of the BA1404, the other R9 feeds the ouput of the amplifier. Inserting 1 to 10 uf chokes in series with these resistors will help clean up the FM-10's output and boost the power output by about 4mw bringing the FM-10's output to 12mw. Use the tiny moulded inductors that look like resistors, or small homemade chokes wound on a small ferrite, not the big honk'n power filter chokes that you get from RS. _________________________________________________________________ 23) COMPONENT/KIT SOURCES The following is a list of sources for items used for modifications, replacement parts, or other kits and equipment used in FM radio transmitting: _________________________________________________________________ 23.1) BA1404s and other FM Broadcaster BA1404s and other FM Broadcaster kits can be found at: D.C. Electronics Tel: 1-800-467-7736 Tel: 1-800-423-0070 Fax: 1-602-994-1707 They sell BA1404s for $2 a piece, seems to be the best deal going. Also they Sell 38KHz crystals for $5.99, which is also a fair deal, the crystals are tiny ones like the digi-key ones, but a different brand and work without problems or the Digi-Key ones. _________________________________________________________________ 23.2) 38KHz Crystals 38KHz Crystals can be obtained by calling: Digi-Key 701 Brooks Ave. South P.O.Box 677 Thief River Falls, MN 56701-0677 +1-800-DIGI-KEY (344-4539) +1-218-681-3380 (FAX) 38.000 KHz by Epson America, Digi-Key part No. is SE3314 (see notes on crystal mod on using this crystal, also note that this is a cylinder type crystal and kinda delicate. You are probably better off getting the 38KHz crystals from D.C. Electronics) _________________________________________________________________ 23.3) FM KITS FROM FREE RADIO BERKELEY Kits to let a thousand transmitters bloom. Lots of FM transmitter and amp kits, mail, email or call for more info. Reasonable prices. Can be slow to deliver (2 weeks to 3 months but promised to get better.) Free Radio Berkeley 1442 A Walnut St., #406 Berkeley, CA 94709 Voice mail: (510) 464-3041 E-mail: frbspd@crl.com Mouser Electronics Mouser Electronics Mouser Electronics 11433 Woodside Ave. 2401 Highway 287 North 12 Emery Ave. Santee CA 92071 Mansfield TX 76063 Randolf NJ 07869 Mouser Electronics 370 Tomkins Court Gilroy CA 95020 Catalog Subscriptions: (800) 992-9943 (Continental US only) Sales & Service: (800-34-MOUSER (800-346-6873) (US, Puerto R., Canada) (817-483-9384) Fax Giant Catalog! 239pages of parts! Just about everything. No min order for north america. $100 min for overseas. RF Parts (transistors) 1320-16 Grand Ave San Marcos, CA 92061 Just about any RF transistor! Dalbani 2733 Carrier Ave. Los Angeles, CA 90040 (800)325-2264 USA (213)727-0054 WORLD (213)727-6032 FAX RF transistors and other semiconductors + more catalog. 178pgs $20 min order Panaxis Productions makes some very high quality FM transmitters. The last word in Transmitting, tons of kits. (Right next to my old place of study Chico State!) Panaxis Productions PO Box 130 Paradise, CA 95967-0130. (916)534-0417 Catalogs are $2, well worth it, a must have item. A little taste of there catalog: MMC1 Macromod Compander for 2:1 compression Plans $12, PCB $18, P+P 26.50, Full kit $87 SG High performance stereo generator Plans $15, PCB $13.5, P+P 26.50, Full kit $105 FME PLL FM exciter Plans $17.5, PCB $15, P+P 24.50, Full kit $129 More expensive than a FM-10 but much higher performance. A company called Progressive Concepts sells plans for a 88MHz to 108MHz amp. The power curves show that 12mw in will yield 2.5 watts, but can be driven harder for up to 12 watts. (I have not seen these plans) Plans only in U.S., $16 (a bit spendy, ouch!) Progressive Concepts 1313 N. Grand Ave. #291 Walnut, CA. 91789 If your looking to purchase a FM-10 kit (or a PA-1 kit) and can't find one locally try: Ramsey Electronics, Inc. 793 Canning Parkway Victor, New York 14564 Phone (716) 924-4560 FAX (716) 924-4555 Should be $29 _________________________________________________________________ 23.4) The makers of the infamous BA1404 Rohm Corporation Rohm Electronics Division 3034 Owen DR Jackson Business Park Antioch, TN 37013 Tel: (615)-641-2020 (ask for someone who deals with the BA1404) Fax: (615)-641-2022 Also they list: Rohm Corporation PO Box 1399 Antioch, TN 37011-1399 _________________________________________________________________ 24) OTHER RAW INFO the 2SC2570 is supposedly replaceable with an ECG10. Also I have used an MRF901 for a replacement, though tough to mount, try bottom of the pc board and connecting the whip antenna pad to ground plane. MPS901s seem to replace the 2SC2570 directly, same case too, check the pinouts though. I have also been told that MPS918s work well also. The MRF239 can be used as direct replacement for the Ramsey 2 meter PA-1 kit. Cost is around $14 bucks. Newark also has the 38KHz crystals for $2.90 ( I don't know Newark's address, this was sent to me in the mail, will try to find it though.) _________________________________________________________________ Please check attribution for Author. Processed by filipg@paranoia.com [Feedback Form] [mailto]. The most recent version is available on the WWW server http://www.paranoia.com/~filipg [Copyright] [Disclaimer] LOW POWER TRANSMITTER KIT SOURCES FAQ Contents: * 1) Introduction * 2) Ramsey Electronics * 3) DC Electronics * 4) Panaxis Productions * 5) Supercircuits * 6) Free Radio Berkeley * 7) North Country Radio * 8) Xandi Electronics * 9) Tentronix * 10) Progressive Concepts _________________________________________________________________ 1) INTRODUCTION Author : Rick Harrison E-mail : hrick@world.std.com Subject: Low Power Transmitter Kit Sources FAQ Date : Sat, 6 Aug 1994 Here is a brief list of companies selling low power transmitter kits. Please send me information about any companies not listed, so that I can include them in future versions of this list. Note to newcomers: to assemble these kits, you must be able to solder components onto a circuit board, and it helps if you know the difference between a resistor and a capacitor. If you haven't reached this stage of electronic know-how yet, consider buying some of the educational kits available from C&S Sales, 1245 Rosewood, Deerfield IL 60015, telephone 800-292-7711. Their electronic components course (item #ECK-10, $14.95) might be especially helpful to newbies. When assembling radio circuit kits, I prefer to use narrow-diameter silver-bearing solder (Radio Shack #64-013) and a 15 watt soldering iron (64-2051). You may need a more powerful soldering tool for making antennas out of large-diameter wire, soldering really large connectors to a printed circuit board, etc., but the 15 W iron works fine for most kits and reduces the chances of over-heating transistors and other heat-sensitive components. _________________________________________________________________ 2) RAMSEY ELECTRONICS Ramsey Electronics 793 Canning Pkwy Victor NY 14564 Tel: 716-924-4560 The FM-10A is an FM stereo transmitter kit ($34.95 plus shipping) with a few milliwatts of output power; it is based on the BA1404 integrated circuit. Ramsey kits have well-written instruction manuals, and most of the circuit boards have lots of wide-open space which makes modifications easy. The company also has a good reputation for service. These factors make Ramsey kits a good choice for beginners, in my opinion. Their AM transmitter kit (item #AM-1, $29.95) and their TV transmitter kit (item #TV-6, $27.95) might also be of interest; however, there is much room for improvement in the design of these two circuits. (Robert Myers of Ramsey Electronics tells me they do intend to release an improved version of the AM-1 kit at some point in the future.) _________________________________________________________________ 3) DC ELECTRONICS DC Electronics P O Box 3203 Scottsdale AZ 85271 The Improved Stereocaster is another FM stereo transmitter based on the BA1404 chip with a few milliwatts of output power ($29.95 plus $3.50 S&H). It has a smooth fine-tuning control which makes it easy to get on the exact frequency you want, and a voltage regulator for the BA1404 which improves stability. Documentation is not quite as lucid as Ramsey's. _________________________________________________________________ 4) PANAXIS PRODUCTIONS Panaxis Productions P O Box 130 Paradise CA 95967-0130 (send $1 for catalog) This company offers many interesting books and kits. The REB-1 kit is a 100 milliwatt transmitter for the upper end of the AM band ($34.95 plus shipping). The FMO kit ($75) is a high fidelity stereo FM transmitter kit with 2 to 20 milliwatts of output power. The FME-500, a half-watt mono FM transmitter with excellent technical characteristics, can be combined with their stereo generator to build a high-quality low power station (> $200 for the two kits). Other items of interest include transmitters for the 1750 meter band; a 1-watt shortwave transmitter kit; and more powerful FM transmitters (available only for export to countries other than the USA). Panaxis kits might not be suitable for absolute beginners; you should have a little experience in circuit assembly before you tackle these. _________________________________________________________________ 5) SUPERCIRCUITS Supercircuits 13552 Research Blvd Austin TX 78750 This company sells a low-power TV transmitter for channels 3 thru 6 which appears to be of high quality ($49.95 plus $4.50 S&H). For licensed radio amateurs, they also sell some ham TV transmitter kits with 1 to 2 watts peak output power that can be adapted for use on UHF channels 14 thru 19, and a linear amp for boosting the output of these transmitters. _________________________________________________________________ 6) FREE RADIO BERKELEY Free Radio Berkeley 1442 A Walnut St., #406 Berkeley, CA 94709 Items listed in their advertisements include a 5 watt mono FM transmitter kit ($55 plus shipping), a 1/2 to 1 watt stereo FM transmitter kit ($50), plus kits for output filters, dummy loads, RF amplifiers, and antennas. Some people who ordered kits from FRB have reported that they've waited a long time before receiving their kits. Others have said they had no problems when dealing with FRB. FRB is spear-heading a movement to challenge the FCC's regulations and is trying to foster a low power broadcasting movement. Contact them for more info. (Internet: frbspd@crl.com) _________________________________________________________________ 7) NORTH COUNTRY RADIO North Country Radio PO Box 53, Wykagyl Station New Rochelle NY 10804-0053 Tel: 914-235-6611 (send $1 for catalog) Many TV-related items: a 50 milliwatt UHF transmitter with crystal controlled frequency ($78); a "video pallete" to create special effects; a switcher that does cross-fades and wipes; and upconverters that will take channel 3 video from a VCR and shift its frequency up to any UHF channel 25 thru 70. For licensed radio amateurs, they have a line of more powerful UHF TV transmitters. With a 100 foot range and a price tag of $62.50, their FM stereo transmitter is not exactly competitive, but it is interesting from a technical point of view. Their stereo infrared transmitter and receiver could be used to build a difficult-to-trace studio-to-transmitter link. _________________________________________________________________ 8) XANDI ELECTRONICS Xandi Electronics Box 25647 Tempe AZ 85285 Tel: 800-336-7389 Tel: 602-894-0992 The XFS108 kit ($41.95) is an FM stereo transmitter, probably based on the BA1404. Their advertisements give no specifics. _________________________________________________________________ 9) TENTRONIX Tentronix 3605 Broken Arrow Coeur d'Alene ID 83814 Tel: 208-664-2312 Another BA1404-based FM stereo transmitter kit ($24). _________________________________________________________________ 10) PROGRESSIVE CONCEPTS Progressive Concepts 1434 N. Mills Ave. Claremont CA 91711 RF amplifiers, FM transmitters and stereo generators, components for RF circuits and more. _________________________________________________________________ Please check attribution for Author. Processed by filipg@paranoia.com [Feedback Form] [mailto]. The most recent version is available on the WWW server http://www.paranoia.com/~filipg [Copyright] [Disclaimer]