Is it really necessary to continue this thread? My inbox is seeing entirely too much drivel like this thread and others on this reflector.
Bob W6TR ----- Original Message ----- From: "Joe Subich, W4TV" <li...@subich.com> To: "'Ignacy'" <n...@arrl.net>; <elecraft@mailman.qth.net> Sent: Friday, December 11, 2009 3:09 PM Subject: Re: [Elecraft] [K3] 150 watt "boots" for 160m > >> 2SC2782 is rated at 80W min each at 175 MHz so getting 150W >> from two on 1.8 MHz should be peanuts; the main reason why >> they are restricted to 110W in K3 is linearity (across bands) >> + component ratings. At higher power, the efficiency can be >> higher and thus K3 may actually run cooler! > > Don't try it ... with 12W max available from the LPA, the pair > of 2SC2782 are already working very near maximum gain at 100 W > output when the other losses are considered. > > The 2SC2782 shows 6.4 dB gain 1t 12.5V ... (12W drive, 80W Out). > Derating the gross output by 1 dB for circuit losses in the LPF > and T/R switch and 1 dB for linearity purposes, the net output > is right at the K3's 110 W maximum output. > > If you really must have 200/250 W output, build an external > amplifier using two MRF-150 instead of the four used in > Motorola Engineering Bulletin 103 by Helge Granberg. See: > http://www.ab4oj.com/dl/eb104.pdf > > In addition to the added power output, operating with a 48V > power supply provides improved IMD (-33 dB @ 150 W) and gain > (>20 dB). > > 73, > > ... Joe, W4TV > > >> -----Original Message----- >> From: elecraft-boun...@mailman.qth.net >> [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ignacy >> Sent: Friday, December 11, 2009 4:06 PM >> To: elecraft@mailman.qth.net >> Subject: Re: [Elecraft] [K3] 150 watt "boots" for 160m >> >> >> >> Those who believe in authority and that God punishes >> tinkerers, PLEASE SKIP this message. >> >> 2SC2782 is rated at 80W min each at 175 MHz so getting 150W >> from two on 1.8 MHz should be peanuts; the main reason why >> they are restricted to 110W in K3 is linearity (across bands) >> + component ratings. At higher power, the efficiency can be >> higher and thus K3 may actually run cooler! >> >> So how to get 150W out of K3? >> >> 1. ALC would not let it. It needs to be fooled, e.g., by >> changing a divider in the SWR unit to indicate 100W when it is 150W. >> >> 2. At 150W the output impedance would not be 50 Ohm; it would >> be 35-40 Ohm with extra impedance added by LPF, which are >> designed for 50 Ohm. You need a manual tuner that you will >> tune for max power, not min SWR. If higher SWR causes power >> fold up, the SWR circuit needs to fooled again. >> >> 3. The radio would take more amps, say 30A, and the fuse may >> go out. If so, change the fuse or reduce the power so that >> the fuse is not tripping. >> >> Is it worth it, I am not sure. In contests, the extra power >> may make a real difference. >> >> Would Wayne and Eric approve? Never officially! >> Would K3 be ruined? I doubt it. >> Would I do it if I wanted to win a 160m contest in LP >> category and had no other alternatives? Perhaps on CW but >> never on SSB due to high IMD. >> >> >> Corresponding story >> Many years ago a power supply for IC-735 broke and the spare >> one was for 5A max. Tuned for min SWR the power was 5 W. >> Tuning for max power out generated 25W. >> Later, I tried the same trick with IC-7000. It was 5 W no >> matter what the tuning because of strong power folding under >> high SWR. Not sure what K3 would do. But there is a >> possibility that one can get 10-20W more just by tuning for >> max power out. >> >> Ignacy >> >> >> >> Julius Fazekas n2wn wrote: >> > >> > Wondering if anyone has a suggestion of a solid state amp >> or "pushing" >> > the K3 PA to obtain 150 watts out on 160m? >> > >> > A kit or HB would be fine... >> > >> > 73, >> > Julius >> > n2wn >> > >> >> -- >> View this message in context: >> http://n2.nabble.com/150-watt-boots-for-160m-tp4151943p4153762.html >> Sent from the [K3] mailing list archive at Nabble.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 > > ______________________________________________________________ > 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 > ______________________________________________________________ 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
