[Elecraft] KPA 500

[Albert Crespo]

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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[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 <f5...@orange.fr> wrote:

[juergen]

Hi Albert

I just looked at the picture of the inside of the THP amp.

http://www.tokyohypower.com/hl-550fx_i_pop.html

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.

I also dont like the switch mode power supply being so close to the high 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 amplifier, however its very ""öpen""

I dont see real value in this amp especially after looking inside it. I would be more inclined to go buy an Ameritron AlS1300 which represents good value and has similar or better construction. It would certainly have better overhead in terms of output power.

73
John
--- On Sat, 2/5/11, juergen <pleb...@yahoo.com> wrote:

[Johnny Siu]

Hello John,

THP is a manufacturer for commercial equipment as well as per their web site. 
I just don't know why their ham amplifiers are so primitive.  They should have
the technology and know how.  My past experience with THP in HF is not
promising. V/U linears are ok.

I would always see linear + ATU as a package.  Therefore, THP + its own
dedicated ATU is not that cheap.  Of course, I shall see how KPA500 + KAT500
come out.

 cheers,

Johnny VR2XMC

________________________________
寄件人﹕ juergen <pleb...@yahoo.com>
收件人﹕ elec...@mailman.qth.net
傳送日期﹕ 2011/2/6 (日) 7:46:49 AM
主題： Re: [Elecraft] KPA 500

[R. Kevin Stover]

THP's amps are anything but primitive.
Check me if I'm wrong but they are the only manufacturer producing a
legal limit solid state amp. The THP 2.5KFX.

Notice I said legal limit, not close to or in the neighborhood, or
might make it if the wind blows just right, but legal limit.

The design for that amp was hashed out on the pages of QEX.

It is expensive but not Alpha 9500 expensive and it is one of a kind.

Why hasn't anybody else designed a legal limit solid state amp?
8 MRF-150's are about the same price as 2 Microsemi ARF-1500's
50V high current DC supply vs 200V high current DC supply (in the box).
Same stupid proof auto-protection systems all the other "not quite
there" amps employ. Well, maybe not. I don't think any of the MFJ amps
will auto band switch without buying their little add-on decoder.

What was that about primitive?

On Sun, 6 Feb 2011 07:58:06 +0800 (HKT)
Johnny Siu <vr2...@yahoo.com.hk> wrote:

> Hello John,
>
> THP is a manufacturer for commercial equipment as well as per
> their web site. I just don't know why their ham amplifiers are so
> primitive.  They should have the technology and know how.  My past
> experience with THP in HF is not promising. V/U linears are ok.
>
> I would always see linear + ATU as a package.  Therefore, THP + its
> own dedicated ATU is not that cheap.  Of course, I shall see how
> KPA500 + KAT500 come out.
>
>  cheers,
>
>
> Johnny VR2XMC

--
R. Kevin Stover
AC0H

[Bob Naumann]

John,

What are your credentials for such a critique without having actually seen
or used the amplifier, and what is your callsign?

73,

Bob W5OV

[David Cutter]

I can't speak for other countries, but here in the UK I used 240V +-7%
(223V to 257V) for normal service but for brown to peak I used 240V +-10%
(216 to 264V), which is very rarely seen here. The 264V is used to test
safety trips and the like according to British Standards such as the the
generic BS3456. Factoring Europe into the equation, I reduce the lower band
to 198V (220 - 10%), so, my designs covered 198 to 264V for safe and
reliable operation. In practice, the lower end often extended to 186V
(-15%). This puts quite a burden on dissipating heat at the top end when
using linear supplies, but is the penalty when designing for extremes if
switchmode cannot be used. Hence tapped transformers to cope with local
supplies.

Being aware of this, I have always been wary of generators when /P or
dxpeditioning and with valve linears getting the heater voltage right with a
true rms voltmeter has always been a concern for me. Small generators often
produce more of a triangular waveform and are poorly regulated well beyond
+-10% key up to key down. With a transistor linear I am concerned about the
peak of the triangle which is higher than that of a sinewave of the same rms
voltage, so, component ratings are very important. On full load, the
problem is distortion as the incoming voltage drops. Some generators also
slow down, increasing the ripple triangle and current into the reservoir
caps.

David
G3UNA
My previous email on this didn't appear on the list, perhaps stuck in
cyberspace.

snip from 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.

.

73
John

[David Ferrington, M0XDF]

I get 240 +- 2v here in Bracknell in Berkshire.
73 de M0XDF, K3 #174, P3 #108
--
No sensible decision can be made any longer without taking into account not
only the world as it is, but the world as it will be.
-Isaac Asimov, scientist and writer (1920-1992)

[Joe Subich, W4TV]

> Why hasn't anybody else designed a legal limit solid state amp?
> 8 MRF-150's are about the same price as 2 Microsemi ARF-1500's
> 50V high current DC supply vs 200V high current DC supply (in
> the box).

8 MRF-150 will not do the job ... that's what is in the ALS-1300
and it's good for 1200 Watts. Legal limit would take 12 MRF-150.

73,

... Joe, W4TV