[CQ-Contest] Sell My Acom for a Tokyo?

Dick Frey - K4XU k4xu at arrl.net
Thu Mar 26 22:53:34 PDT 2009


The largest Tokyo Hy-Power amp at 1500W output, uses two ARF1500s in 
push-pull at 100V. These are very large 500V MOSFETs, easily capable of 
750W output. I quite am familiar with the devices in amp and its PA 
circuit. In case you're wondering, they cost $226 each in small quantity.

These MOSFETs were designed for the industrial semiconductor capital 
equipment market where 13.56 and 27.12 MHz RF plasma is used for 
various  operations in the manufacture of transistors, IC's, LCD panels 
and solar cells. The user's tolerance for failure in this market is nil. 
There are many millions of device-hours on these parts without any 

Due to the ballasting of the individual MOSFET die inside the package, 
the linearity of these parts just happens to be spectacular. Check out 
patent 6,939,743 to see what's inside. They are close to being a solid 
state version of a 3CX800. You can see a prototype schematic of the THP 
amp in the QEX article available at 

THP's next amp down puts out 1kW, and uses four THP2933s. This is a more 
robust version of a similar part, SD2933 made by STMicro. Theirs has a 
higher breakdown voltage which enables THP to use an unregulated 50V 
supply, saving cost and improving over-all efficiency. There is also a 
23 lb version with a SMPS supply.

I am still trying to wear out Titan #1, Alpha 86 #0, and a homebrew p-p 
pair of ARF1500s. But I hear good things about both THP amps and the 
level of service they provide. JA1DJW -- Nobuki Wakabayashi is THP's 
founder and president. He speaks excellent English and is very 
attentive. The big amp's price is less than the several auto-tuning tube 
amps it competes with. They are both well built, smart enough to protect 
themselves from hams, and they do flawless QSK if you want it.

I don't have any connection with THP or its representatives but I would 
not be unhappy to see more high power MOSFETs in use out there. They 
have arrived.


Don't forget - *7QP* is coming to a band near you -- May 2!

Richard Frey - K4XU
61255 Ferguson Rd. 
Bend, OR  97702
Email:  k4xu at arrl.net
Web page: www.codxc.org

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