The Xantrex converters I mentioned will take any input from 14v to 80v and deliver 40 amps out.. the output is actually a full blown 3 stage battery charger... so you really need to have a gel cell on the output, which will double as filtering.. and should work just fine under any load conditions, as one of the unit configurations is as a load diverter.. to direct current to an alternative load when the battery bank is fully charged (for instance, go a bank of grid-tie inverters)
-----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Finch Sent: Tuesday, March 25, 2008 10:05 AM To: [email protected] Subject: RE: [Repeater-Builder] 24 vdc to 12vdc Hello Group, I will say right now, a resistor is a bad idea but it can work of done correctly and the load is a constant. Back before I knew better I did just that. I needed 12 VDC for the filament of a GE Mastr Pro UHF transmitter, I can't remember the current right now, it's been 20 years. I built a DC supply and built a regulator with a 2N3055 NPN pass transistor, it worked OK but the transistor was dropping way to much voltage creating a lot of heat. I installed a high wattage series resistor that was heat sinked to a big aluminum plate before the 2N3055 and with a big Moose of a capacitor on the input of the 3055 to keep down noise. The resistor dropped the input voltage about 10 volts and the transistor ran cool. All of this was before any DC to DC converters were popular or available to the average Joe Ham. The system ran like that with no problem for years, I shut the repeater down and left it on the building, it was not worth the effort to bring it down from the penthouse. As far as I know it's still up there could possibly be fired back up on 444.850 if needed. My friend that got me that site retired so I faded away. The Converters are by far the best but if the load is fairly constant and if all you have to work with is a series resistor and a regulator it can work. Also, you don't have to buy these from Astron, you can buy small "bricks" that do this same thing and all you have to do is add some capacitance to the output unless they have variable outputs. Don't know what Astron gets on their units but I have several 48 to 5, 12 and 24 volts units in service now like the ones below. Here are a few, I have used the Powerstream and Murata products in the past. http://www.vicr.com/ http://www.v-infinity.com/ http://www.powerstream.com/dcdc.htm http://www.murata-ps.com/mps-home.html Again, don't get me wrong, THE DC to DC CONVERTER IS BEST! Just trying to avoid flames. Paul -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Tuesday, March 25, 2008 7:34 AM To: [email protected] Subject: Re: [Repeater-Builder] 24 vdc to 12vdc Rick, Definitely do not use a resistor. Its drop depends on current draw and if the rig is a transceiver it will draw much more current on TX than RX changing the drop. You can use the lower battery, the one connected to ground. However, as some others suggested might be better to have a 24-to-12 V converter. 73, ron, n9ee/r >From: Rick & Charlotte <[EMAIL PROTECTED]> >Date: 2008/03/24 Mon PM 02:21:31 CDT >To: [email protected] >Subject: [Repeater-Builder] 24 vdc to 12vdc > >I hope some one on the group can help me out here > >I want to put a radio in a jeep > >the problem is the jeep runs 24 v and as you know radios run 12v > >Is there a device that will drop 24v down to 12 vdv ? I know I could use a >droping resistor but I can see it making a lot of heat > >if I remember right the jeep uses 2 12 v batts can I just tape off one set for >the radio ? > >I know this is not about repeaters , but just thought some one might have >an idea .. > >Thanks > >Rick > >Of all the intelligent animals, Human is the species that is least likely to learn >from its experience. >That explains why so manny of us have more then one Border Collie ! > >== www.karolinabc.ca == > >Rick,Charlote & Kids >Our Border Collies >Miss Daisy Duke >Sir Red-A-Lot >Miss Elly May >Mr Boots >Mr. Balue >Our Border Collie Message Group >[EMAIL PROTECTED] > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. ------------------------------------ Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 7.5.519 / Virus Database: 269.22.0/1341 - Release Date: 3/24/2008 3:03 PM No virus found in this outgoing message. Checked by AVG. Version: 7.5.519 / Virus Database: 269.22.0/1341 - Release Date: 3/24/2008 3:03 PM ------------------------------------ Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG. Version: 7.5.519 / Virus Database: 269.22.0/1341 - Release Date: 3/24/2008 3:03 PM
