You should be able to one of those items. You pick! Sent from my iPhone ...nr4c. bill
> On Apr 21, 2017, at 6:15 PM, Bill Johnson <k9...@live.com> wrote: > > This is impossible to resist buying. Sell the car, the house, the Wife... > nope on the last. > > 73, > Bill > K9YEQ > > -----Original Message----- > From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Wayne > Burdick > Sent: Friday, April 21, 2017 2:25 PM > To: Elecraft <elecraft@mailman.qth.net> > Subject: Re: [Elecraft] KPA1500 PIN diode T/R, fans > > Hi Paul, > > To protect the amp and T/R switch, we’re using heavy-duty PIN diodes, very > high reverse voltage, and virtually instantaneous detection of high SWR. All > possible catastrophic load scenarios have been extensively tested. > > On fans: > > We started with a humongous custom heat sink extrusion and thick copper > spreader, optimized for our packaging. We also use two LDMOS devices rather > than one, allowing heat to be distributed across all that heavy metal much > more effectively. This slows fan onset time. (Some competing compact amps use > inadequate heat sinking, with predictable results.) > > Next, we added three large, deep fans. The center fan is controlled > independently so it can turn on first, at low speed. In many cases that's all > you'll ever hear. Only during high duty-cycle operation are the other two > fans turned on. We then carefully manage the speed of all three. > > Ultimately, you have to get rid of the heat. But our goal is always to > minimize noise. > > 73, > Wayne > N6KR > > >> >> *From: *"Paul Christensen" >> >> Wayne, >> >> Congrats on what looks like a very well-designed amp. I've been >> waiting on an amp with these features for a very long time. Of >> particular interest to me is your continued use of PIN diode T/R >> switching. Can you describe SWR protection to the Rx PIN diodes at >> the 1.5KW level? I suspect that a fast-detecting SWR switch will be >> the main focus of protection, as well as HV back-biasing of the Rx >> diodes. An open or short RF termination requires over 900V DC to keep >> Rx PIN diodes from going into conduction. Can you describe this area >> of circuit protection just a bit? >> >> Secondly, I know that fan noise is difficult to quantify in words. >> Anything >> particularly innovative you're going to minimize cooling noise? Thanks! >> >> Paul, W9AC >> >> >> >> >> --- >> This email has been checked for viruses by Av ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
