I have a Lunar-LInk System 72 (432 mhz) Amplifier using a pair of 3cx800 (perfectly designed by K1FO SK), in a cubic package that may actually be smaller than the KPA1500 (of course the power supply is external, and the blower and T/R relays are attached to the back of the amp). I had a choice of Dayton blowers, one for ssb/cw (60 CFM if I recall correctly) and one for moon-bounce or key-down modes (100 CFM, I think). I got the 100 CFM blower, anyway the one that moves more air; 100 CFM makes a lot more noise!
The only discussion about blower noise was to provide this choice (sometime after I got my unit it became possible to purchase the 100 CFM blower but it ran at two speeds). I imagine that levels 4, and 5 are related to key down modes in KPA1500, and maybe level 3 as well. I suppose one can reduce fan or blower noise to some extent by paying attention to relevant details about fan and noise but all significant variables held constant (like the size of the amp and the power output), there is no free lunch (as usual), solid-state or not. I recall the conduction cooled amps (no fan, no noise), one by Henry Radio (2 x 8873) and another by Heathkit (one 8873). You had to reduce power significantly for key-down modes, and neither amp made 1500 watts output rtty key-down (1000 watts cw for the Henry--but of course this was before the current maximum legal power output). Still, how long you could hold down the key depended upon ventilation of the amplifier. Heathkit recommended only 200 watts output for rtty. I imagine guys placed fans (making some noise) near the heatsinks! So, to put this into perspective, how long the key can be held down using kpa1500 at 1500 watts output power may have something to do with fan speed number five! If you want "almost silent high power", then try running kpa1500 at 500 watts output (about like a conduction cooled amp--but don't hold that key down too long without ventilation). 73, Will. wj9b CWops #1085 CWA Advisor levels II and III http://cwops.org/ CWops #1085 CWA Advisor levels II and III http://cwops.org/ -------------------------------------------- On Sat, 6/2/18, Jim via Elecraft <elecraft@mailman.qth.net> wrote: Subject: Re: [Elecraft] KPA-1500 Fan Noise To: "John Perlick" <jperl...@ariacorp.com> Cc: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net> Date: Saturday, June 2, 2018, 6:20 AM I don’t have a dog in this fight - someone who spends half the year (the half with all the good contests) in a Florida condo is not a candidate for buying amps. But might water cooling be a possibility? As in a heat sink that sits in water, with appropriate thermal shutoff if the water/amp get too warm? And when that happens, get fresh cool water. 73 - Jim K8MR > On Jun 2, 2018, at 4:06 AM, John Perlick <jperl...@ariacorp.com> wrote: > > Bill Schmidt is right--you have to get rid of a bunch of heat--no matter what device you are using to amplify (tubes, transistors, or magic). The amplifying device must dissipate considerable heat because we are running Class AB and because of all electronic devices are naturally lossy. > > Remember that this heat is generated not only in the RF transistors, but also in the power supplies, bias circuits, lights, etc. There are lots of heat sources in every amplifier. > > I can honestly say that my KPA1500 is considerably quieter than the Expert 2KFA that I just sold and I would have to say it is quieter than my old Alpha 87A. I do operate it at full 1.5 KW output but I suspect my duty cycle on CW has not caused it to so how that the fans max out. Same for the 2KFA, but even at low speeds, it was far noisier. And, the 2KFA has REALLY loud T/R relays! > ______________________________________________________________ > 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 jimk...@aol.com ______________________________________________________________ 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 wlba...@bellsouth.net ______________________________________________________________ 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
