[Elecraft] KPA 500

[juergen]

Hi Albert

The old standard of 220,230,240 volts +- 10% has been gradually deteriorating to plus minus anything! 

The mains voltages  in many places now goes up to and regularly runs at 260 volts! The global de-regulation and privatization of power assets globally has seen standards  go down the drain everywhere.

Most quality switch mode power supplies are designed for voltages   as high as 260 high volts with a plus 5% rating. Many designers and export countries have not caught up with the global deregulation of mains voltage standards. In many places this has been allowed to happen in the hope that a global standard will develop.

I can buy energy saving globes that are rated to work at 260 volts(Philips). Many  TV's from the Korean companies are designed to  work at 260 volts. There is still a lot of new equipment designed for either 220 and 230 volts nominally. This  well defined standard is hardly the  reality anywhere these days even with the +- 5% allowance


The Tokyo high power amp looks interesting. They appear to be using VRF150's. If they have  biased this amp very well they will achieve good IMD results.  

SPE amplifiers using the MRF150's dont achieve the best IMD performance which can be obtained from  these devices. The Yaesu FT-5000's PA appears to be very well designed. The 3rd order IMD figures in Class AB according to the reviews are almost as low as Class A at 200 watts of output. They use VRF150's This a is a very good achievement by Yaesu and is a benchmark in terms of IMD performance.

I doubt that the Tokyo High power will achieve such good results because THP have always used just the bare minimum bias on all their amp designs. IMD optimization has never been a design goal of theirs. I had a good chat with the designer one day and he was open and candid about this issue.

Mt homebrew MRF150-EB104 amp easily achieves -40db 3rd IMD figures on all bands. My surplus ERB MRI amplifier  which I bought on Ebay does even better than -40db 3rd order. These are all below one of 2 tone figures not PEP figures. 

The Elecraft KPA500 will use VRF2933's for which  no IMD data  is provided on the data sheets. I dont know why Microsemi leaves out this important data. Macom religiously supplies extensive IMD data versus bias current which makes choosing devices very easy.  Anyway this will hardly be concern for anyone since the radios always have worst IMD performance than  the amplifiers.

I will watch the reviews and see how they both perform, the market is getting crowded! I will make my donation once I know how well they perform. It would be nice owning a  compact 500 watt amp  that performs well without all the mess and surplus rubbish hanging off the amp.

73
John
 

--- On Sat, 2/5/11, Albert Crespo <f5vhj at orange.fr> wrote:

> From: Albert Crespo <f5vhj at orange.fr>
> Subject: [Elecraft] KPA 500
> To: elecraft at mailman.qth.net
> Date: Saturday, February 5, 2011, 9:43 AM
> Tokyo High Power has produced a 600
> watt amplifier,  HL-550FX , http://www.arraysolutions.com/Products/THPtop.htm   that
> can handle a wide range of voltages, so it is ideal for
> places with bad  voltage regulation. Will the  new
> amplifier that Elecraft will produce will have this same
> ability?
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