Three here. Chuck WB2EDV
----- Original Message ----- From: "Paul Finch" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Tuesday, March 25, 2008 12:17 PM Subject: RE: [Repeater-Builder] 24 vdc to 12vdc > Did everyone get this email three time like I did? I only sent it once. > Sorry bout that.... > > Paul > > > -----Original Message----- > From: [email protected] > [mailto:[EMAIL PROTECTED] On Behalf Of Paul Finch > Sent: Tuesday, March 25, 2008 11:05 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 > > > 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 > > > > ------------------------------------ Yahoo! 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