[Elecraft] SSB IMD

[Joe Subich, W4TV]

> Jan Erik Holm wrote:
> > 
> > Bill and others, hold on and think about these
> > figures. -35 to -38 dB IM3 !! We are dealing
> > with 2SC2782 transistors operating at around
> > 12V DC. I say no more, the knowledge and intelligent 
> > individual will understand.

I would be careful here ... the Toshiba 2SC2879 data sheet 
clearly does -38dB IMD at 60 watts with VCC=12.5V.  There
are certainly devices capable of that level of performance  
means that there are devices capable of that level just as 
there are devices capable of similar levels of performance 
at 120-140 watts per device with Vcc=28V. 

I would expect the 2SC2879 to also be capable of this level 
of performance ... if not, I would have expected the design 
of the KPA3 to have been based on another device. 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill W4ZV
> Sent: Monday, January 26, 2009 4:18 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] SSB IMD
> 
> 
> 
> 
> 
> Jan Erik Holm wrote:
> > 
> > Bill and others, hold on and think about these
> > figures. -35 to -38 dB IM3 !! We are dealing
> > with 2SC2782 transistors operating at around
> > 12V DC. I say no more, the knowledge and intelligent 
> > individual will understand.
> > 
> 
> Which reminds me...I set my power supply to deliver 14.5V at 
> the input to my K3 terminals under load.  Although the power 
> supply specification says...
> 
> "Supply Voltage/current: 13.8 V nominal during TX. (11 V min, 
> 15 V max). 17-22 Amps typical in TX (100W). 0.9A minimum RX."
> 
> ...I would never intentionally run mine at the lower end of 
> that range.  If you have any concerns about overshoot when 
> turning on your power supply, always turn the PS on a few 
> seconds before the K3.  I tend to leave my PS on continuously 
> so overshoot is never an issue.
> 
> IMD performance should be much better at the upper end of the 
> voltage spec than at the low end...and I believe I've seen 
> Eric or Wayne recommend this previously but have not searched 
> for the exact quote.
> 
> I'll let you tell W8JI he's not knowledgeable and intelligent.  ;-)
> 
> 73,  Bill
> 
> -- 
> View this message in context: 
> http://n2.nabble.com/New-Eham.net-K3-review-by-QRPNEW-tp221808
6p2220726.html
Sent from the Elecraft mailing list archive at Nabble.com.

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