At 02:07 PM 7/11/2008, Gerald Youngblood wrote: >The finals have two 470 uF caps in paralles (940 uF) right at the PA RF >chokes and another 470 uF at the driver for a total of 1410 uF on the 13.8V >bus. That does not count a string of 0.1 uF caps in parallel. > >Gerald
1000 uF isn't all that much in an application drawing amps, where the load peaks are on the order of milliseconds. So.. assuming that at full power, voice peaks, you're drawing about 15 Amps, the cap voltage drop will be about 15/(2*470E-6) -> 16V/ millisecond (assuming no replacement energy from the bus). The bus has a fairly low impedance, though, so it's not that bad. Figure the wires have a resistance of about 0.02 ohms, or 0.3V drop with the 15A load, so when you go from zero to full power, the bus voltage drops that much. When the load goes on, the capacitor will supply energy for the first few 10s of microseconds, then it's basically all done. Think of the filter capacitor as being the C in an RC time constant with the R being the load resistance (about 1 ohm, here). I suspect you need a MUCH stiffer power supply, if you're operating at a level where the voltage on the amplifier makes a difference. _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
