3CX800s were used in a number of Henry Amplifiers sold for ISM service,
VHF and UHF. I know of several that have been used to drive
superconducting resonators and particle bunchers for scientific
applications. But these are not high volume markets, more like dozens of
sockets.
Glass tubes such as 3-500Z have gotten difficult to produce because
manufacturers of the glass tubing have gotten out of that business. The
Far East is attempting to pull together what Svetlana couldn't, but I am
still not convinced the quality is there, although its been 5 years
since my last purchase of a 3-400Z from China was a bad experience. We
still use these in 6-8 sockets at work, non RF.
I still promote tubes with ceramic metal construction for many
applications, although nothing under 5 kW any more. Hams are slow to
adapt to the change, and they have some peculiar design constraints that
Jim Thomson mentioned, including broad bandwidth, protection from VSWR
and overdrive, cooling in a small box, need for switched low pass
filters, and IMD performance. These are all areas that a tube amplifier
can do it simply, although they are getting costly too due to small
volume tube production. There is no simple answer either way.
The Freescale, NXP and other new 50 V LDMOS parts are interesting in
that they can just about do what a 500Z can do, when properly protected.
Advanced Power Technology (APT) in Bend, OR (now Microsemi) was a
pioneer in high power inexpensive MOSFETs for ISM. Many years ago the
late Helge Granberg of Motorola built the MRF154 and later variants. Big
hunking DMOSFETs, that were higher gain, and a lot of power capability.
Being expensive parts, these were quite fragile, and never really took
the high power market by storm. A lot more MRF151G are still being
installed and used in thousands of applications. I met with a very
experienced solid state amplifier designer from CERN in Switzerland in
May, and he is building new power modules (1-10 MHz 500 W) using
MRF151G, as he has many hundreds of them in service,they are available
from several somewhat equivalent sources, and they have become commodity
transistors like the 3-500Z was to tubes.
In the scientific market, several users are demanding high power solid
state now, fixed frequency UHF mostly. Levels like 100 - 200 kW are
becoming common in some facilities. Linear amplifiers.
So I don't believe it is productive to shoot down a new tube or solid
state amplifier these days, as both have their places.
73
John
K5PRO
> Message: 5
> Date: Sun, 29 Jul 2012 19:57:27 -0500
> From: Gary K9GS <garyk9gs@wi.rr.com>
> Subject: Re: [Amps] Dedicated RF
> To: amps@contesting.com
> Message-ID: <5015DBF7.60100@wi.rr.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Exactly Carl....there are still plenty of 3CX800 tubes floating around
> and pulls are fine for existing amateur equipment.
>
> Heck....if I came across a good deal on an amp that used 3CX800s I might
> be tempted to buy it. Buy a couple of pairs of spare tubes and I'd
> probably be set for my lifetime. But I wouldn't rely on an iffy supply
> chain for new production. Just think about TenTec and the 4CX1600.......
>
> I thunk the 3CX3000 is an excellent choice...plentiful in the supply
> chain and a market exists outside of the amateur radio market.
>
> Does anyone know if there is a market for the 3CX800 outside of amateur
> and replacement for MRI?
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|