Joe, Very interesting. Not too surprising.
I am building a CCI HF 300w amplifier kit (Motorola Engineering Bulletin: EB-27A), that uses 28-volt transistors. I bought a matched pair of the Toshiba equivalent for the MRF-422 (2SC2510 rated at 150w/each; power gain = 12.2 dB). IMD min (-30 dB) is at 85w. The K3 will drive it possibly to 200w output (100w per transistor). Running at 170w would probably be the cleanest level. Table-I in the engineering bulletin shows Harmonic performance (2-30 MHz) http://www.communication-concepts.com/eb27a.htm http://www.communication-concepts.com/appnotes/EB27A300Sharp.pdf If I like how the amplifier turns out, I may start building a few of these for the ham radio market. Ed - KL7UW ---------------------------------------------------------------------- Message: 1 Date: Thu, 15 Apr 2010 10:20:28 -0400 From: "Joe Subich, W4TV" <[email protected]> Subject: Re: [Elecraft] Ten Tec never sounded so good! To: "'Tom W8JI'" <[email protected]> Cc: [email protected] Message-ID: <85e31a466596414d860b7ac081725...@laptop> Content-Type: text/plain; charset="us-ascii" > For all those intent on boosting low power radios with a > cheap external PA, you can see measurements here: > http://www.w8ji.com/rm_hla-150_test.htm > > The very best the RM Italy amp gets on *any band at any > power* is about like a FT1000MP on the very WORSE band for > the MP. If you had not documented that the transistors were only rated for 70W PEP, I would have thought that one of the push-pull pair was open with those results. I don't know what transistors are but those IM plots would suggest the bias is incorrect - which might be logical if RM Italia are using an undersized heatsink. > There is no convincing people that our 100 watt radios at > 100 watts are barely acceptable as is, and that all these > little tricks that give another 1-2 dB more power can > increase splatter 15 dB or more. Worse yet, those cheap > illegal amplifiers that make 10-watt radios into 100 watters > are going to be our undoing. Very true ... we would be better off with 48V transistors with power levels below 200W PEP. There are several devices capable of 3rd and 5th order IMD better than -40 dB at that power level. 73, ... Joe, W4TV 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010 DUBUS Magazine USA Rep [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
