They bias the LDMOS devices at 1 amp each. That is minimal in overall heat when you are pulling over 40 amps at high power.
Dave wo2x Sent from my waxed string and tin cans. > On Aug 29, 2019, at 1:29 PM, David Gilbert <[email protected]> wrote: > > > This was discussed here not long ago, and it is normal for any linear > amplifier. It needs to be biased up to be linear, and that bias energy ends > up as heat even if you don't use it. > > I worked as a component engineer at Collins Radio in Cedar Rapids when I > first got out of college. One of the low level RF stages (or IF stage, I > don't remember for sure) in several of their receivers used a stud-mounted RF > power transistor biased up hard enough to discolor them. > > 73, > Dave AB7E > > >> On 8/29/2019 6:03 AM, Roger D Johnson wrote: >> It's interesting that the heat that has to be dissipated is pretty close >> to 1000 watts in all these scenarios! Running the amp at less than full >> power buys you nothing. >> >> 73, Roger >> >> >>> On 8/29/2019 8:38 AM, Larry (K8UT) wrote: >>> Pete, >>> >>> I don't run my amp at full legal limit on digital modes, but typically set >>> the input power for about 1000 watts output. One of the interesting >>> characteristics of the amp is increased efficiency as power increases. At >>> 600 watts efficiency is only 38%, whereas at 1000 efficiency increases to >>> 50% and at 1500 watts to 60%. >>> >>> (see screenshots) >>> >>> -larry (K8UT) > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
