I am not impressed with the construction. It looks a lot like an Ameritron
inside. At most it looks like a EB104 CCI amp with a power supply and a low
pass filter board in a box. The cooling looks to be primitive at best.
pass filter board. This is a recipe for noise and other problems. There is
also a general lack of shielding. This might be ok for for 500 watt
I dont see real value in this amp especially after looking inside it. I
value and has similar or better construction. It would certainly have
> From: juergen <
[hidden email]>
> Subject: Re: [Elecraft] KPA 500
> To:
[hidden email], "Albert Crespo" <
[hidden email]>
> Date: Saturday, February 5, 2011, 3:33 PM
> 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 <
[hidden email]>
> wrote:
>
> > From: Albert Crespo <
[hidden email]>
> > Subject: [Elecraft] KPA 500
> > To:
[hidden email]
> > Date: Saturday, February 5, 2011, 9:43 AM
> > Tokyo High Power has produced a 600
> > watt amplifier, HL-550FX ,