At 05:11 AM 01/09/07, Nate Bargmann N0NB wrote: >* IF YOUR NICE I MAY TELL YOU <[EMAIL PROTECTED]> [2007 Jan >09 06:55 -0600]: > > Hi all you know they say there is no dumb question unless you didnt > > ask it and messed things up so here goes .I am wanting to make a cheap > > repeater system for 2 meter and I really need some input on how to put > > one together and also once its built is there a special licence to > > operate it?Thanks 73'3 > >If you're in the USA, no special license is required so long as you >hold a Technician class or higher. The first thing you need to do >before investing time and money is to contact your local frequency >coordinator and get a frequency pair coordinated. Without proper >coordination, the FCC will hold you fully accountable for resolving >interference to a coordinated system.
Don't be surprised if many coordinators WON'T give you a frequency, at least at first. The two meter band is FULL in most areas - locally the waiting list here is measured in decades. Get a repeater directory and plot the repeaters in a 100 mile diameter circle in your area, then borrow a 100w mobile, and drive to the highest ground in your area. Key up with each of the 32 PL tones on every channel, even those that aren't in the book (not every repeater is listed). You may discover, as the ones around here do, that every channel has at least one high level or two or three low level systems. So they chose to go to 52Mhz, 220MHz, 450MHz, 900mhz or 1200mhz. Another reason for the coordinator to look skeptically at you is that over the years they've been burned by too many well intentioned folks that don't follow through. This is why in many areas there are what are called SNP channels - Shared Non Protected pairs that the coordinator tells the potential system builders to build their systems on. Once the coordinator (or his agent) can kerchunk your system for himself (and not from right in front of your house) then he knows that you are for real, and issues you a real frequency. Around here the coordinator even helps you sell off the "test pair" channel elements to the next newbie. >As for "cheap" equipment, as the equipment gets cheaper, your >investment in time increases. It's almost a linear relationship. That >said, I've had good results with a pair of Motorola Mitrek mobile >radios. There is not enough isolation within one radio at 2 meters to >get by with only one. Also, the modifications are fewer when two >radios are used, plus you can make them to be a ready spare for the >other function. And some of the "off brands" like Aerotron go for "get it out of my garage" prices. For years one very good local machine used an Aerotron 100w UHF transmitter and a Motorola Micor receiver (the club jokingly called it a "Micor-tron"). The problem with off-brands is twofold: finding documentation,and finding help. The latter can really hurt - if you were to pop up here and say something like "I have a high band Micor and can't get the exciter to tune down from 155mhz to 146.82mhz" you'd have several folks walking you through the process, and maybe one or two offering extra boars in case yours was bad. And I remember a couple of cases where one reader drove across half a state to help another get a system on the air. If you had a Repco, or a Uniden, a Aerotron, or a Ritron, you'd find that you'd be very very lonely... >To be really cheap, you'll have to avoid the duplexer. So, this pretty >much dictates a "split site" repeater which adds the complexity of a >link between the receive and transmit sites. Also, a split machine >will suffer from uneven coverage between RX and TX. If you have a decent antenna structure at both ends the link can be fleapowered. I've seen a split site repeater with a 250 milliwatt link on 420MHz, and it was a hop of over a mile. The key was the (homebrew) 420MHz Yagi antennas on each end. The particular repeater is a continuous duty GE Mastr II station (originally on 46MHz, moved to 52Mhz) that the owner swapped the receiver out with the one in a 420mhz UHF mobile. The mobile sits at the other site with the low band receiver installed and the transmitter PA deck disabled - the exciter is jumpered to the antenna feedline. >Duplexers aren't cheap even when bought used. That's very true - they don't depreciate. And you want to be careful of the ones on eBay, as they might have been nailed by lightning, or be damaged. I saw one that had a bullet hole in it. >Once purchased >they need to be tuned onto the correct frequencies. This is easily >done with a tracking generator, but can also be accomplished with >a signal generator and a spectrum analyzer. And the equipment to do that is EXPENSIVE, but it only has to be done once - and I've heard of it done in exchange for a tank of gas and lunch. Just treat that just-tuned duplexer as if it was a case of thin shelled eggs. With some brands you get a huge percentage of the performance with a 10 degree twist of each screw, and all it takes is one good bump... I've seen one guy strap a UHF duplexer into the passenger seat with three pillows around it and the shoulder belt... And DON'T use the harness as a carrying handle. >Then there is feedline and antenna. Nothing less than hardline will do >and avoid fiberglass antennas like the plague. Uless you like chasing >noise problems... Nate is referring to this article: <http://www.repeater-builder.com/antenna/cracking.html> Next, I'd read this article for an overview / review: <http://www.repeater-builder.com/rbtip/repeater101.html> It was written, by request, from a rank beginners point of view, and may be too basic in some areas for the members of this mailing list. The next reading to do is at: <http://www.anglelinear.com/repeaters/repeaters.html> Then I'd read most of the theory articles at this web page (ignore the spec sheet pages and drawings for now) <http://www.repeater-builder.com/antenna/ant-sys-index.html> Then start connecting up with the existing repeater owners in your area. Get to know them. Express an interest in putting up a "garage" repeater, "just to get some background in them". You will probably find that some equipment gets offered. Don't take everything without doing some research, as you may find that some of it is outright junk, or at least not practical - for example, the Yaesu commercial repeaters that start with the prefix "FTR" are no longer supported (no docs or parts). The microprocessor based repeater controllers made by Creative Control Products are good, but the company is out of business, and the source code has been lost. On the other hand, some old stuff is worth it - if you get offered a GE Mastr-Pro or Mastr-Exec II base station, take it. It's a very good "starter" radio. You might find that a local repeater owner that is tired of the "owner" role, and is ready to turn over operation of an in-place system. A UHF system changed hands here several years ago for a couple thousand dollars - a 90w Motorola repeater, Celwave duplexer, at a commercial site that was under $200 a year on a 10 year lease (the site lease was worth more than everything else combined - local rates are $100 to $200 a month). If this happens, take it, but ask the former owner to be available for consultation. This article may be interesting: <http://www.repeater-builder.com/rbtip/checklist.html> Mike WA6ILQ
