From One Newbie to Another A Tiny TX -n- Tool Guide For the Perplexed, the Vexed and the Unlearned! By lysdexia@evansville.net INTRODUCTION: So you wanna be an FM Broadcast Buccaneer? Mmmm... Pablum... Mmmmm.... How's about another deeelicious laxative ad? Mmmmm... Loud demands for purchase of products I don't need, padded out with Spudulous Cretin music chosen for digestability, blandness, quick recognition and "broad appeal." *Gak* "News" that can hardly be distinguished from commercials. "Public" radio that has all syndicated news and sattelite-fed music from central sources, just like commercial stations. *Urp* It's Radio In The `90's.... God, please bring armegeddon and that right quickly! ...or maybe you would rather help yourself to a chunk of that bandwidth and do your part as a rational, passionate, thinking human. You can give your community a _real_ choice, rather than an ongoing Coke/Pepsi ad war disguised as an "alternative." Imagine: News that actually happened! Music from local musicians! Letting people tell their stories as they wish: not in hacked-up slickly edited sound bites designed to create petty controversies that obscure the real problems in your commmunity. Alleluja! It's not as hard as you might think. All it takes is some skull sweat, patience, time and about 200-500 bucks spread over a couple of months (this includes tools and stuff- you can get off much cheaper if you are a student!...) a careful attitude towards the law and an enormous ego! This little opus is far from comprehensive- but it may help you ask the right questions later. God knows I have asked (and still ask!) some really stupid ones. Don't be afraid to look like a dork on usenet! For every -=Smug_Bastard=- on alt.radio.pirate who makes a nasty, whithering comment you will have two or three good, helpful suggestions from people who have made the mistakes for you! (Don't worry pally, you'll make your own!) I personally am very impatient and suck at details- yet I still have a decent, clean signal and pretty good range- you can too! __________________________________________________________________________ PART THE FIRST: Modulating That Electricity Like a Bargain-Basement Tesla! Or, The Bare Bones Broadcaster Busts the Bandwidth. To broadcast you must have the following (in order): A purpose, Airspace, Know-how and tools, a station and listeners. 1. A PURPOSE You have to supply this from your own head. What do you want to say and do? Who are you trying to reach? And most importantly: why should your audience care? Having a good grip on this will help you make intelligent decisions on everything from content to hardware later. I chose to do my station because the music scene in my town is great- yet the local stations are practically all satellite based. This makes it difficult for local musicians to get space- micropower to the rescue! 2. FINDING AIRSPACE This is fun work here- Drive around in the area you want to broadcast to in a car with a good synthesized tuner and find the clear channels! You should do this in clear and cloudy weather, day and night- find that clear spot. Interfering with another station's signal not only unduly annoys the competition, it sucks for the listeners and gives the whole micro-broadcasting thang a bad image. To really get to your listeners you have to be clean and clear. Think about it: do you like to listen to a cruddy signal? Nyet. You can do a quick search at http://www.jagunet.com/~kodis/station.html. It will scope the stations in your area and generate a nifty map for you to use. The problem with trusting this otherwise excellent service is: the schmucknitians for your local stations may have overmodulated their signal to make it sound "Louder" in the quest for higher ratings. This means that their audio going into the transmitter is too strong, which causes the TX to "splatter" onto other parts of the band near their designated area. This shithead behavior makes for an fm dial full of crud and will render your online research less effective. The only way to be sure is to listen around for a clear spot! 3. KNOW-HOW AND TOOLS BOOKS (The place to start getting the know-how) There are several REALLY helpful books out there that can give you a good understanding of how radio works- The ARRL handbook should be in any public library and will give you in-depth information on the nitty-gritty of modulating static to your own ends. Pay _CAREFUL_ attention to the portions concerned with filtering of your signal! "The Practical Antenna Handbook" by Joseph Carr (TAB Books, 2nd Ed. ISBN 0070111057) is absolutely invaluble. It will explain the basic of antenna design and take you well beyond them in no time. If you buy one book in this hobby I humbly suggest that this be it. One can have a great transmitter with a bazillion watts and fantastic sound, but if your radiator is not up to snuff you might as well be sticking your stereo speakers out the window! If you are an absolute beginner at electricity in general, may I humbly suggest "Electricty 1-7" by Harry Mileaf (Editor-In-Chief). This is the bomb book for learning about electricity from the ground up! (groan) A series of books that can save you time and money in the long run is a volume or two of Rudolph Graf's "Encylopedia of Electronic Circuits" (available from www.northcountryradio.com) The volumes are chock full of power supplies, amps, compressors, limiters and a zillion other things that you can build for yourself, without shelling out for the expensive stuff.... Read up a little bit before you start into this hobby- it will save you time, money and, perhaps, your bacon (where the FCC is concerned). Steve Quest occasionally posts a good intro to radio theory. (Post it again! Pbpbpbpbpblease!) 4. TOOLS (Most can be found at the local Radio Shark!) A good, hot soldering iron (around 15-20 watts). A supply of thin 2% silver solder (really thin! Your dads plumbing solder won't work- save it for the antennas!) A Volt-Ohm meter or Digital Multimeter (DON'T SKIMP HERE! YOUR VOM WILL BE YOUR BEST FRIEND!) LD Brewer sells a nice one with an SWR bridge built in. A set of small wirecutters, needlenose pliers, (yes!) baby fingernail clippers, screwdrivers, hacksaw and wire strippers. The usual toolbox crud. A set of small files (handy- not imperative though...) A plastic index box from Wally-Mart or a sewing store to keep all the miscellaneous electronic crap you will attatch itself to you like stink on a monkey. A scientific calculator. (cheap at wal-mart!) A set of coax crimpers and the fittings of your choice. (Those big CB "f" connectors are probably best.) A dummy load for testing your transmitter without hooking it to an antenna. A low-power one is butt-easy to build! Basically a 50 ohm resistor soldered ground to + across a coax fitting. (Invaluble!) A friend with very little feeling in his or her hands to hold stuff for you while you solder. Radio Shark sells a neato little soldering stand. (I call mine R2-D2...) These are the _very_ basic tools you need to put a transmitter together, build an antenna and get the sucker up in, and on the air. This ain't rock collectin'! You don't have to buy all this stuff at once- but I gaurantee that you will own 90% of it before your TX will put out a good signal! Start getting tools while you are reading. By this time you will be ready to begin work on your..... ______________________________________________________________________ 5. STATION You will need to gather the following items for a station: An audio source- a microphone, a tape player, you get the idea. A mixer- so's you can talk and jam at the same time A Transmitter (duh)- There is a long list of those below. An RF amplifier- ditto. An antenna Transmitters: A Preamble The funnest part of this whole hobby is buying, assembling, debugging then utterly destroying in a fit of rage, your first transmitter. Most people (I did anyway) start out by purchasing an FM-10a from Ramsey Electronics. They can be ordered straight from Ramsey or bought from Radio Shark from their "Unlimited" catalog. These transmitters are, for the most part, crud. They sound (in my opinion) like shiznit, have lousy range, put out a really dirty, harmonic laden signal and drift off of their chosen spot on the band like a demented butterfly. To be fair to Ramsey though, A trained ape could build an FM-10. If you can follow the easy, complete directions that come with the FM-10 you can have noise coming from your stereo (and maybe your neighbors stereo- if he lives less than a block from you) in an evening. I alternate between wanting to kiss or kill Ramsey. They get lots of people into the hobby and on the air for cheap- but dang that thing sounds bad! With a better quality PLL-type kit you will have probably have very few problems with harmonics and spurious signals- maybe.... the problem is that when tinkering to get the best power output from your TX (short for transmitter) you might be putting out bad signal: and without a lot of really good equipment (like a spectrum anylizer! Yow! $$$$!) you will never know for sure and be tempted to skip the $15.00 for an output filter. DON'T DO IT!!! In building an FM-10 you become INTIMATELY FAMILIAR with harmonics! When first tuning your FM-10 in you will hear at least one. It is not uncommon for a newbie to actually tune the TX to the harmonic- and get terrible sound and range. (Hmmmm, how do I know this? Guess.) Ramsey also sells PLL kits, but both are hampered by the use of the BA1404 chip which attempts to do everything- stereo, carrier, oscillator and does none of them really well. These kits are designed to be toys! Think of them as such! *Whew* Enough of my Ramsey-bashing... Recently there has been a bit of a renaissance in transmitter kits. Makers like Panaxis and Free Radio Berkely that produce solid kits have been around for years. The relative newcomers like Veronica, North Country Radio and Wavemach seem to be just as nice if not better. Most of the discussion around the newsgroup have been about personal preferences and price rather than the all-out flamage that can occur in other areas of the hobby (like antenna design and How Much Range Can I Expect....). In other words: the above kits have been reported to be reliable, pretty easy to build and clean- maybe better than the local commercial station! Lots of people ask about micropower radio transmitter manufacturers. Here is a list of sources and their wares I compiled while searching for my own best choice. Perhaps one of them will be useful to you. I do not claim this to be the "KING GAWD LIST OF TERRIBLE COMPREHENSION TO WHICH NO MAN MAY ADD AND SURVIVE!" It is far from comprehensive: to make it thus, please forward any other addresses, phone, URL or other info on new manufacturers of FM transmitter kits to me and I will add it to this posting! I do not have permission from any of the businesses or groups listed herein. I am posting this as a service to the micropower community and its boosters. Any mistakes are my own. I am not an employee or even a buddy with any of these guys. This is not spam... sorta like potted meat. _________________________________________________________________________ LD Brewer Http://www.ldbrewer.com (800)886-8023 (813) 980-2287 What can I say? These guys kick ass. They have well-deserved rep for supplying you with the stuff you need and giving advice that you can use. I cannot say enough good about them! They carry kits from Ramsey, Veronica, Free Radio Berkely and audio stuff from Dennon and Gemeni. They Rock! Power Supplies, Wattmeters, Microphones, 7 and 9 Pole Filter kits COMET CFM-95-SL antennas, Custom Transmitters and lots more! Try to find it here first! __________________________________________________________________________ Free Radio Berkely 1442 A Walnut St. #406 Berkeley CA. 94709 (415)464-3041 Email:frbspd@crl.com (many of the Kits FRB sells are available from L.D. Brewer- http://www.ldbrewer.com- as well. You should probably order from them as they will most likely have the actual kits in stock and will be available to help should something go awry.) Steven Dunnifer is fighting the good fight in court and with these kits (check his homepage!). There have been a few complaints on alt.radio.pirate about slow service and weird parts substitutions: You should be aware of this! However, the folks I have communicated with who own his kits say they work great, are well designed and rugged! I have one of his 20 watt amp and 5 element filter combos and it works great! Guess it's like owning an older jeep: they are inexspensive and tough, but you gotta have some know-how to get it going. (These prices and descriptions are taken from FRB's catalog that I ordered in November of `96 and may not reflect actual prices.) 1/2 to 1 Watt PLL Transmitter Full digital PLL control locks the frequency an prevents any drift from happening. Will easily drive the 6-8, 1-15 and 40 watt amplifier kits. Easy to assemble. (Available in almost assembled form, just 10-12 components to solder in, for $155) 6 Watt RF Amplifier Uses a rugged 6 watt transistor. Designed to boost low wattage transmitters to a bit higher output and will produce up to 8 watts. A very small and compact circuit 3x1 1/2 in. for 1/2 watt imput drive. Easy Quick assembly. Requires 12-14 Volts DC at 3/4 to 1 amp for operation. 15 Watt RF amplifier Uses a very high gain (14db, power gain of at least 25X) RF transistor to boost a 1/2 watt input to 15 watts. Measures 2 1/12 by 5 in. and fits into a 4x6 enclosure (available punched and drilled.) Includes heat sink. Easy, point to point surface mount assembly. Requires 12-14 volts at 2 amps for operation. (Tons more- I did not include them for brevitys sake) FILTERS It is absolutely imperative to use a filter to prevent interference from harmonics generated by the transmitter. Both these filters start to roll the signal off at 108-110 MHz or so. Not using a filter will create problems and give the FCC ammunition to use against microbroadcasters. A clean signal is essential to the success of this movement. (WORD! -D) Output Filter Kit A seven element low pass filter, composed of 4 coils and 3 capacitors, to flatten those harmonics. This one works well with the 6 watt ane 15 watt amplifiers. Heavy Duty Filter Kit A nine-element low pass filter, which will handle power levels to at least 100 watts. Use this filter with the 30 or 40 watt amplifiers. Enclosure is $15. Lots more available! Dummy loads, antennae, power supplies, coax, etc. _________________________________________________________________ CANA-KIT http://www.canakit.com Don't know much about these kits. They appear to be BA1404-based stereo VFO kits that tune from 86-98 mhz and claims a range of 500 meters with a whip antenna. At $43.95 it might make a good dormcaster... __________________________________________________________________ Panaxis Productions Box 130 Paradise CA. 95967-0130 (916) 534-0417 This guy has been selling kits for years and has a reputation for putting out high-quality products. I will update this to reflect his current offerings when I recieve his new catalog. (The following was horked from the LD Brewer Homepage- don't sue me!) The Panaxis FMX is a PLL based transmitter kit with some very unique features. Builder selectable audio allows the use of 'PRO' broadcast audio equipment, consumer line level input, or speaker level audio input. BUILT IN AGC nixes the need for a limiter if configured in the low impedance design. Postive NO-TUNE operation is a plus, and frequency selection is easy via the rotary freq. select switches. The fellows at LD Brewer and Progressive Concepts sell his TXs and stereo generators as well. ------------------------------------------------------------ North Country Radio P.O Box 53 Wykagyl Station, New Rochelle, N.Y. 10804-0053 (914) 235-6611 Vox (914) 576-6051 Fax (518) 854-9280 Tech support Email: ncradio200@aol.com or 102033,1572@compuserve.com http://www.northcountryradio.com For around $75.00 you can get the MPX96- a phase locked loop transmitter with onboard stereo and preemphasis. It sounds great and is easily strapped to 150mw output. (one can apply about 18-20v to the output, upgrade some caps and an output transistor and get reliable signal in the 230 mw area!) From the NCR web page: PLL Synthesized for accuracy (0.1 KHz or better, adjustable) with digital receivers Easy construction and setup, with VOM and audio source RF output filter for clean RF and low harmonic output less than -50 dBc No obsolete, drift prone, unstable BA1404 used Excellent audio quality and separation, noise and spurs -60 dBc or better, separation 30 dB Audio response 20 to 15000 Hz, std preemphasis built in, takes standard line level audio Operates from 12-14V DC supply at 125 ma Small size 4" X 4", rugged epoxy fiberglass G-10 PC board used Fits into our NC1500X metal case All signals accessible for educational and service purposes Covers 88 to 108 MHz and 76-88 MHz (used in some nations), 100 KHz steps 19 and 38 KHz MPX signals crystal controlled On board audio generator (1187 Hz) crystal controlled, for testing. The MPX96 will be useful anywhere a short range low power FM audio link is needed. It is far superior to free running FM transmitters and will not drift off channel, and perfectly compatible with digitally tuned FM receivers. It is also useful as a teaching aid, unlike low end units using a BA1404 or other black box IC, allows access to all MPX signal waveforms and the observation of the process of signal generation. The circuit is adjustable for optimum performance, and if no test equipment is available, works well with default settings, so anyone can get satisfactory results with only a VOM or a DVM. In the USA and certain other countries, signal radiation must be kept to a level low enough so as not to exceed specific field strength levels and not to i nterfere with other stations using the FM broadcast band. Check with the applicable laws in your nation, such as the FCC or DOT rules and regulations. In the USA Part 15 of the FCC rules and regulations applies. (I use this particular TX- I think it godlike!) ______________________________________________________________________________________________________ Veronica Kits 18 Victoria St. Queensbury, Bradford BD131AR, UK 44 1247 816 200 http:www.legend.co.uk/~veronica Veronica has a butt-load of neat, inexpensive kits. The one listed here is their latest (as of 2-13-97). There are higher powered kits available. They are distributed in the states by L.D Brewer (L.D. Homebrewer?). You can reach L.D. Brewer at http://www.ldbrewer.com- and I suggest you do! The fellows are helpful to the extreme, know what they are talking about and will not sell you a bunch of crap you don't need. They also have a sense of humour- which will help you keep your own when you screw up! TECHNICAL SPECIFICATIONS Frequency Range: Programmable from 87.5 - 108MHz Frequency Generation: Crystal referenced Phase Lock Loop Frequency Stability: Better than +/- 1 KHz max, typ +/- 500Hz Spurious Emissions: Better than -45dB reference to carrier RF Power Output: 900mw minimum RF Output Connector: SO239 Power Supply: 13.8v DC regulated Audio Input Sensitivity: 0.775 V rms for +/- 75 KHz dev Signal to Noise Ratio: -75 dBu Audio Frequency Response: Flat from 20 Hz to 76 KHz Pre-emphasis None, 50 uS or 75 uS Audio Distortion: Better than 0.2% THD Audio Input Connector: Phono Socket PRICE KIT FORM: 65 Pounds (english) ASSEMBLED & TESTED: 99.95 Pounds (english) ___________________________________________________________ WAVEMACH COMMUNICATIONS 320 Dixon Road, Suite 302, Etobicoke, Ontario Canada M9R 1S8 (No Email or WWW yet.... pending) (416) 243-2260 Vox (416) 243-1067 Fax (Attendez Vous! Wavemach kits and completed TX's are now available from Progressive Concepts! See Above!) This fellow builds the very interesting-looking FMS2 and attendant power amplifiers, power supplies etc. They are available fully assembled or as kits (call Progressive Concepts!) FMS2: Dual crystal controlled Dip switch selectable in 100KHz increments Freq range 75MHz to 125MHz Automatic level control 2:1 audio compressor Audio buffer/preamp High performance preemphasis and roll off filter RF Metering circuit Harmonic filter On board switching power supply Audio Response: 20-20KHz Max Audio Level: 245v RMS Input Impedance: 100K Output Impedance: 50-75 Ohms Distortion: 0.2% Stereo Separation: 40db Noise: -65db Deviation: 75 KHz Output: Ver1 500mw Ver2 200mw Spurious Output: -40db Channel Res.: 100KHz Freq Range: 75MHz-125Mhz Current: 500ma Voltage: 8-12v (12v recommended) Board Size: 5x6 1/4" Version 1 (500mw): $295.00 US Version 2:(200mw): $285.00 US FMS2 Schematic Only (ver 1&2): $27.00 US FMB2 Power Booster (2 1/2 watts) $55.00 US FMB2 Power Booster Schematic Only $12.00 US 5/8 wave Antenna (3.4 dBI) $135.00 Power Supply: $87 (ouch!) ____________________________________________________________________________________________________ 6. COAX AND ANTENNAE Coax For most low-power applications (a watt or so) Belden RG-58 coax is okay. For long cable runs or power in the 50 watt or above range one should go for _at the very least_ RG-8. Get the good stuff with a foam core- the coax I have gotten from Radio Shark is shite. Make sure you grab a heap of those nifty little zip-ties too. Electrical tape sucks in high winds, Jimson! There are some who swear by twinlead (which is supposed to be very low-loss) but I have never fooled with it. Below is a synopsis of a conversation that appeared on alt.radio.pirate concerning coax. I have removed all names exept L.D Brewer's and my own due to privacy considerations. If you see your words here, and would like to have your name on them, feel free to email me and I'll put it back! COAX SHOOTOUT! Douglas \"Lonely Planet Boy\" Shawhan" wrote: >Cost-B-damned, No-holds-barred best 50 ohm coax for a run of 100 feet >pumping 20 watts or more: Your votes? >d --------------------------------------------------------- My vote goes for 1-5/8" heliax and larger. Low loss. --------------------------------------------------------- Well for only 20 watts you can use pretty much anything I would guess that either RG/59 or RG/58 (one of these is 50ohm, the other is 75ohm). Both of these are fairly low loss and for 20W you'll have no problems at all. If you're going to start pumping more power then I would suggest RG/8 which offers good power handling and price. Seriously though - you're only going to encounter problems when you start upping the power out. I've quite successfully run 75W on the thinner coax with no problems. If you aren't getting out well enough some meatier silicon is often cheaper than a long run of expensive coax. --------------------------------------------------------- >Well for only 20 watts you can use pretty much anything I would guess >that either RG/59 or RG/58 (one of these is 50ohm, the other is 75ohm). >Both of these are fairly low loss and for 20W you'll have no problems >at all. >If you're going to start pumping more power then I would suggest RG/8 which >offers good power handling and price. >Seriously though - you're only going to encounter problems when you start >upping the power out. I've quite successfully run 75W on the thinner coax >with no problems. >If you aren't getting out well enough some meatier silicon is often cheaper >than a long run of expensive coax. Cheaper and dumber. Never mind the loss factors or that the stuff doesn't last, but cheap, poorly shielded coax also has a rather nasty tendency to radiate a lot of harmonics and other unwanted garbage. My personal opinion is that anyone who wants to run 20 watts (or more) at 100MHz through a hundred feet of RG-59u is either out of their mind or has no concept of what they are doing. But that's just my personal opinion:-), *Good* RG-8 is fine for HF but starts to get pretty lossy at FM broadcast frequencies. My vote for best stuff cost-be-damned? I'd say get some RG-214u w/the silver-plated conductors. Goes for a bit more than a buck a foot last time I checked. A radio tech friend of mine was lucky enough to have free access to a big spool of this stuff from the shop he worked at -- so he ran it w/ a CB rig! Talk about waste & overkill........ ------------------------------------------------------------------- : Well for only 20 watts you can use pretty much anything I would guess : that either RG/59 or RG/58 (one of these is 50ohm, the other is 75ohm). : Both of these are fairly low loss and for 20W you'll have no problems : at all. That would be totally INSANE to run any 100 MHz signal for 100 feet on RG-58 or 59. At least half the power would be lost in the coax. NOT GOOD!! Use RG-8 at the minimum! ----------------------------------------------------------- There are many types of coax, some that are made of a solid outside jacket that looks like the flexible electrical conduit. This is commonly known as Heliax, but that's a brand name, from Andrew. There are probably others. It's expensive, too. But it's low loss, since the center conductor is supported by rings of teflon or something similar. It can handle a lot of power, thousands of watts. But you said you didn't care about cost, so.. You could probably get by just fine with the popular and much talked about Belden 9913. ------------------------------------------------------------ > > Cheaper and dumber. Never mind the loss factors or that the stuff > > doesn't last, but cheap, poorly shielded coax also has a rather nasty > > tendency to radiate a lot of harmonics and other unwanted garbage. > The quality of coax has nothing to do with the radiation of harmonics. If your transmitter is generating harmonics, the best coax in the world will not keep them from being radiated. You must eliminate the harmonics at the transmitter. ------------------------------------------------------------------------- Try Belden 9913, short of hard line it is pretty good. You could use the mini-hardline that is flexible from Andrews as well. Really Famousguy -------------------------------------------------------------------------- Hi Doug, Incredibly Niceguy in England calling. I'd agree with both ***** and Mr RG-214 above. There's no such thing as overkill where coax is concerned, especially at VHF freq's. I'm surprised no ones put Cable X-Perts name forward, they are down the road from you in IL. Tech info 847-520-3003, e-mailcxp@ix.netcom.com Freephone on 800-828-3340 (orders only) This co' advertises in the ham mags. Loss factor is loss factor, every db is worth having, get that antenna up higher than high at VHF, or consider a co-linear, alternatively if you're on the edge of your town or city consider a directional array. Several of the FM boys here in London use yagi's from the tops of tall high rise buildings! I use Andrews LDF to feed a 340ft wire on 1.8Mhz, also to feed the tower on this band. No, there's no such thing as overkill, but will the bank account stand it? ---------------------------------------------------------------------------- 1-5/8 IS nice !! You have to have a good tower just to support the stuff however ! Currently, I am using 7/8 Andrews, and at 100 Mhz there is little or no loss. For the average hobbyist, we recommend Belden ( or equiv. ) 9913. This is a semi rigid air-dialectric 50 ohm cable, which has about the same loss at 100 mhz / 100 ft as Andrew 1/2 inch hardline. We sell the 9913 with connectors attached ( PL-259 ) for $75.00 / 100 We also sell a good quality ( low loss ) RG-8 w/ connectors for $28.95 / 50 ft , and $42.95 /. 100 ft. Whatever you do, don't try to run Rat shax RG-8 ( or 58 ) in longer runs than about 20 feet. The braid is so loose on that stuff that most of your signal will leave the coax before it ever reaches your antenna ! Remember, a good quality antenna, ( and feedline ) are the MOST important components of a Micro-Radio station !!! L.D.Brewer 2-Way Radio http://www.ldbrewer.com ldbrewer@flanet.com 1-800-886-8023 ---------------------------------------------------------------- Belden 9913 ----------------------------------------------------------------- Has anyone seen the loss specs for the mini-8 coax sold for CB sets or whatever? I have seen pieces of it, and it's the same size as RG-59, but has a larger center conductor so it's lower impedance. It has foam dielectric for low loss. And it's supposed to be better than RG-58. I've seen it used between a 400 W linear and an antenna, so I know that it works, at least for CB. ------------------------------------------------------------------------------ >I'm using Belden 8214. Anybody know the difference between 9913 and 8214? 8214 has a foam dialectric.. 9913 is air dialectric, and has a continuous foil sheild supported by a 90% braid. Very much better than 8214 as a rule. 8214 on the other hand is much better than *most* el-cheapo cable out there ! ------------------------------------------------------------- > > >You could probably get by just fine with the popular and much talked about > >Belden 9913. > > I'm using Belden 8214. Anybody know the difference between 9913 and 8214? > > Thanks A lot less loss. 9913 is the next best thing to regular old hardline but costs a lot less, weighs a lot less and is somewhat more flexible. 9913 has a dialectric that is mostly air with a plastic spiral to keep the co-axis apart. When dealing with low power signals either transmitting or receiving and runs over about 40 feet it is the way to go to not loose precious signal... (and not much $$ extra) -------------------------------------------------------- ******, turn down the voltage a minute and spend a few less $$$$$! This 2013 has almost an air dialectric with the same plastic spiral but it doesnt sell for a buck or more a foot only 35 cents a foot to 500 then 33 cents a foot. ----------------------------------------------------------- Hmmmm... never heard of 2013. The last 50 foot chunk of Belden 9913 I bought cost me 35 bucks. I have seen it a little less somewhere else since then, but that is ballpark. --------------------------------------------------- Go for RGB-213 cable....hardly any loss ---------------------------------------------------- After some more up-to-date reasearch. I must reconsider my vote. Athough RG-214u still beats the hell out of RG59, I must admit that it does in fact display a 0.6 dB greater loss factor than Belden 9913 per 100 feet at 100Mhz -- a diffrence which is somewhat academic considering it would take 500 feet before producing a 3dB diffrence, which as I'm sure you all know is generally considered the lower limit of human perception relative to subjective loudness. Nevertheless, 214 does display an obvious and measureable inferiority. HOWEVER, this does not mean that my vote for "cost be damned best 50 ohm coax" now goes to 9913. Nay, in fact based on my recent reasearch I now chose Andrew LDF5-50A. $5.75 per foot. --------------------------------------------------------- A 1 or 2 Db difference at the transmitter site cannot be noticed at the receiver. So why the big fuss over fractions of Db loss in coax? The lowest loss feed line is balanced or open wire (ladder) line. The old timers knew this and built their antenna systems based upon that fact. VSWR and line loss is a factor for both transmitting and receiving. An antenna tuner is used with open wire feed line and a dipole fed this way can achieve very good results on all the H.F. bands. Hope this helps some.... ----------------------------------------------------------- Heliax 1-5/8'' is best if you need pretty close to zero loss. Its still expenesive even here in the us. As another alternative which performs quiet well try and get some RG-8U 50 ohm heavy duty coax. what ever you deside on use N connectors at least at the mast end to couple your feedline to the antenna. And for a good Antenna that offers low angle radiation use a slim jim, This type of antenna beats hands down even some of the more aclaimed broadcast type antennas. Works real well if you stack two of them in a phased array config. -------------------------------------------------------- Hello: Normally, the VSWR will not show much of a difference between good and junk coax at 100 feet. What will happen is a MAJOR power loss at higher frequencies. Try this. Get 100 feet or so of good ole junk RG-58. Hook up the transmitter to one end and a dummy load or antenna to the other. First hook up a power meter between the transmitter and the coax. Take a measurement. Then put the power meter on the other end between the coax and antenna. At 400mhz or so, you will see about a 15x drop in power!!!! Put 30 watts in and you get about 2 out!!! At HF, the losses are much much less. I don't have a chart in front of me, but I seem to remember about a 1 to 2 db loss at 20 meters. Most coax shows a fairly linear loss as frequencies increase. Remember that a 3 db loss is HALF POWER LOSS! Every db is huge when driving the antenna. At microwave frequencies, the hardline coax can cost way more than the radio itself. Hope this helps. ------------------------------------------------------------- I am just a dumb ham but it is a shitload cheaper and a hell of a lot better to mount the amplifier on the antenna mast or tower and run the DC power and RF through some relatively cheap coax. You will also get all of the amps power to the antenna this way. It's your money though. ------------------------------------------------------------------ ------------------------------------------------------------------ So there you have it: the overwhelming majority go for Belden 9913 as the best compromise. Dissenting votes go for hardline or putting your amp up on the antenna mast. (dc power loss over long distance make this a dubious proposition unless you have a power supply that can handle the vagaries of weather..) Antennas Hold on! This is where the big flames start! There are several different types of antennas, and the one you use can depend on your skill level, your cash flow and your directional needs. There are many more types of antennas than I list here- check the ARRL Antenna book for more. An antenna is a radiator that sends your signal to the reciever. A properly tuned antenna is your key to longer range and a good, strong signal. In fact, a good antenna is more likely to give you range than masses of power! There are a couple of things to consider when choosing your antenna. First is polarization. Most commercial stations are circularly polarized. The simple explaination is that the signal coming from a circularly polarized antenna is picked up equally well by an auto antenna (vertically polarized, meaning it is vertical to the earth, or ground plane) or a home stereo (horizontally polarized). The main drawback to circular polarization is that you get negative gain. (More on gain is later. For now think: "More gain good, less gain bad.") That is why you see some commercial stations with several "bays" of weird-looking curliques going up and down the tower: having three or more "bays" helps to make up for the loss inherent in the design and get more gain by adding more length to the radiator. If your audience is going to be folks in cars and students in dorms listening in on cheap jamboxes, then you probably want to go with vertical polarization. If your listeners will be owners of nice home stereos- horizontal. And there is always the dreaded cross-polarized dipole! Seriously folks, most of us are operating at around 1-20 watts, so a vertically polarized gain antenna like a J-Pole, Ground Plane or a Yagi is probably best. I will tell how I made a dipole and a J-Pole, and give overviews and follow-up info on others and update this as I experiment with them. DIPOLE This is the easiest antenna to make. The recipe I used for a dipole is basically two 1/4 wavelength pieces of 1/2" copper tube set end-to-end with a 50 ohm balun between. The + lead from the balun goes to one side, the - lead to the other. Here is how I built mine: First, the math. Divide 234 by your wavelength (say 89.5). This will give you the length of your elements in feet. To wit: 234 \ 89.5 = 2.61 feet. Now I don't know about you, but I don't relish trying to figure out .61 feet- it seems dumb. So I always convert to metric like so: 2.61 feet x 12 = 31.32 inches, 31.32 inches x 2.54 = 79.5 cm So there you have it: two elements 79.5 cm long! It is a _lot_ easier to get an accurate measurement this way than futzing around with all the fractions, don't you think? (If any of you Euro Cats can clue us into the straight-from-metric measurement I will be happy to put it in here- we are silly here in the states!) I made a simple set of sliding elements for my dipole for fine-tuning thusly: cut your dipole elements about 1/2" short. Take two 3" sections of scrap copper tubing and cut a 1/4" longitudinal section from them (that's "longways") Squash the sliders a little and slide them into the outer ends of your elements. They should be pretty tight. Sliding elements for $0! (If you really want to be clever, I guess you could put copper caps on the end, but mine worked fine without them.) I mounted mine on a 3 foot board by drilling through an inch from the edge every 8 inches and putting a zip-tie through the hole and around the elements. I just nailed it vertically to my windowsill! (watch for metal gutters a wavelength or less away!) Tune with an SWR meter and you are ready to go! A properly tuned dipole has no gain, but that is no biggy as it is not particularly lossy either. Make sure you use a 50 ohm balun! Not using a balun causes your feedline (the cable from the transmitter to the antenna) to radiate signal. That makes for a weaker signal at the antenna high SWR (Standing Wave Ratio) and terrible range. Don't be fooled like I was and use one of those stupid tv 300 to 75 ohm baluns from the Radio Shark! Get a good 50 ohm from a ham supplier! CROSS-POLARIZED DIPOLE Very similar to a regular dipole. Just add two more elements in an "X" pattern so that you have two negative and two positive elements at right angles to each other. Put on crossed boards and mount like you would a regular dipole. Weave yarn through it to get that macrame' look (this is called the "Jan Brady" camoflage effect) and your landlord will think it is a `70's wall hanging or a dream catcher. Kill me. The main drawback in a cross-polarized dipole is that it has negative gain, like a circularly polarized antenna. This is no big deal if you have a small area to cover (like a small college campus) or have power to burn. You will probably need at least five watts to get a 3/4 mile radius with a cross-dipole on the third floor of a building...... J-POLE Talllllllll antenna! Good gain, fairly easy to tune and make with two pieces of 1/2" copper water pipe, a hacksaw, torch, some solder and flux paste and a fist full o' zipties! This is the second antenna I built and I had fairly good luck with it. A J-Pole is (duh) shaped like a letter `J'. The tall part of the `J' recieves the + side of your coax. The small part gets the - side. Please see http://www.svn.net/mycal/mpr/jpole.htm for the plans I used. GROUND PLANE More to come! YAGI More to come PART THE SECOND: LEGALITY. AIEEEEEE! ___________________________________________________________ This file was written using the Joe text editor under Linux 1.2.13- Free Unix! Free Radio! Free Humans! All props to those who helped me and others get our mouths on the ether! ___________________________________________________________