Tony, Why DTMF controlled? If the batteries run down because no one starts the generator, you'll be unable to start it remotely, and have to go to the site. Use a repeater controller which has enough smarts to monitor the system, start and stop the generator automatically, page someone when there's a problem, and provide a DTMF override of the automatic functions if needed.
How secure is your site? A generator and fuel supply could be attractive resale opportunities for meth addicts. Then again, so might solar panels or a wind turbine. You haven't mentioned how your site is laid out, or how much space you have, but wind may be a good alternative. If you determine a realistic power budget, you might be surprised at how small a wind turbine would keep the site up. With enough reserve battery capacity and a repeater controller programmed to load-shed by reducing power when things get tight, much can be done. A few months ago, I looked into small turbines, and found one designed for portable use by motor home owners. It had blades about 1.3m in diameter, and IIRC would be capable of 200+ watts continuous in a 15 mph wind. A hybrid system with wind and solar can reduce the needed turbine size even more. Although, if you get below about 600 watts, wind turbines start looking more and more like toys. I'm guessing a wind generator made for occasional use on a sailboat mast wouldn't last the winter in Alberta. The MSR2000 may not be the best candidate for alternative power, since its idle current draw will be significant, and reducing transmitter power will not produce a proportionate drop in current consumption. I'd guess the GMR300s also have relatively high idle current. I once ran a UHF repeater using Repco RFID data boards. The 2-watt transmitter drew 750 mA at 13.8 VDC when transmitting; the receiver drew 24 mA at idle. The S-Com 7K's 100 mA drain turned out to be the biggest item in my power budget, even after I added a Motrac helical preselector to the receiver. I used a single, 42-watt (@ 14V) solar panel and a 100 AH marine deep cycle battery, which would have allowed continuous key-down operation for over four days with no sun. At 200', it was a very useful repeater for downtown public service events, and even rag-chewing among suburbs. I built a crude solar regulator with a relay which latched to take the panel offline when the system voltage reached 14.4V for the first time each day. Since the relay coil was powered by the panel, it automatically dropped and reset at sunset. A logic input on the 7K sensed the latching of the relay, and would send a DTMF burst decoded remotely to track what time each day the system reached full charge. (Usually mid-morning.) The macro fired by that logic input also altered the courtesy beep and lengthened the repeater's tail, so I could determine the regulator's relay status even if I missed the daily status page. At sunset, the dropping relay sent another DTMF page, and the courtesy tones and tail time reverted to their "night" mode. A logic output from the 7K was connected to momentarily unlatch the relay, in case I wanted to remotely start a second daily charge cycle in the afternoon. With 4+ days of battery backup, I never needed to do so, but it was nice to know I could always top off the battery the afternoon before a hurricane was coming, etc. But, alas, FM land mobile users don't like weak signal work, and I eventually bit the bullet and went to a GE Mastr II and AC power. You may also find, as others are suggesting, that commercial AC mains with battery backup is the most cost-effective option in a practical system. Paul, AE4KR ----- Original Message ----- From: Tony VE6MVP To: [email protected] Sent: Thursday, May 08, 2008 10:55 PM Subject: [Repeater-Builder] DTMF controllable propane generators Folks We're moving a VHF MSR2000 repeater and two UHF GMR300 linking radso's to a site where commercial power will cost $5000 plus monthly fees. So we're looking at various options such as solar, wind and so forth. The land owner might not appreciate another wind turbine so one idea we're thinking about is a DTMF controlled propane generator. Has anyone experimented with such? I see mention of remote control generators so figure it should be doable. The current controller is a RLC-3 but that could be changed if it would help. The other obvious answer is to have the generator automatically come on when the voltage gets too low but I wonder how well that will work. We're in central Alberta, Canada so the days in winter are quite short and we can get 20 or 25 cloudy days in a row. We either need to put in a *lot* of solar panels or some other form of auxiliary power. Also the site may be accessible only by snowmobile for a number of months in the winter. We also will have to ensure that if the temperature looks like it's going to get colder than -35 for an extended period of time we'd better have the batteries charged right up as propane won't "gasify" colder than that. Thanks, Tony
