Thanks Roger!
I'm benefit a lot from it.
----- Original Message -----
From: "Roger (sub1)" <sub1@rogerhalstead.com>
To: "Hsu" <hsu4qro@gmail.com>
Cc: <amps@contesting.com>
Sent: Wednesday, November 17, 2010 5:19 PM
Subject: Re: [Amps] 2010 Handbook
> On 11/16/2010 7:11 PM, Hsu wrote:
>> I do not know why ARRL stiill published so old article,
> They do have some new topics of which I am particularly fond. <:-))
>> as you know, the 4CX1600B is rare and expensive part.
> The 4CX1600B is not only rare, as I understand it is no longer
> produced. It was, in my estimation, a great tube, but apparently there
> wasn't enough demand to justify continued production along with economic
> difficulties in the producing country.
>> It is bizarrerie, why few person using 4CX1000A?
>> It has legal power.
> I can guess of a few reasons although they may not be valid I think they
> exist.
> 1: The tube has zero grid dissipation. With a proper circuit that
> is not a problem with a tetrode, but it carries a stigma and one I
> believed for a while.
> 2. It only has 1000 watts plate dissipation, yet that is more than
> enough to get the US legal limit. Alpha uses a pair of them in the
> manual tune amp.
> 3. It was used in the 30S-1 and associated with only about 1200 watts
> max out even if that amp was designed to the OLD US specs.
> 4. It uses an oddball socket, although it is the same socket as the
> 4CX1500B uses and basically the same as the Chinese FU728F
> socket except for the size of the centering pin. (easily fixed if you
> want to exchange tubes)
> Maximum frequency for full power is only 110 MHz, but I believe
> it will operate at 144-147 MHz at reduced ratings and a pair in PP will
> easily run more than the legal limit. Basically the three tubes
> mentioned are interchangable except for the filament voltage and that
> centering pin.
> 5. maybe the most important, the 4CX1500B will do almost anything the
> 4CX1000 will do and it's more rugged.
> 6. The Chinese FU728F will do most any thing the 4CX1000A will do for
> about half or less than half the price.
> 7. 4CX1500B tubes seem to be readily available.
> 8. A single 4CX1000A is good for for about 2000 watts out while the
> 4CX1500B is good for roughly 2600 watts out (PEP). So is the FU728F even
> though it is officially rated at 1200 watts plate dissipation.
>
> One thing I like about these tubes is they will operate in any position,
> not just vertical with base up or down. At least the two US tubes will
> and I believe the Chinese tube will as well.
>
> One other point, here in the US Triodes are the configuration of choice
> and Tetrodes and not all that popular.
> Part of this has come about due to the FCC regulations with gain
> limitations or drive power that were in effect for several decades.
>
> Another is that a number of triodes from the 3CX800 through the 3CX3000
> to CY156 are available as pulls at reasonable prices and will operate at
> higher frequencies at full power. Although the CY156 has a very long
> warm up time when used any where near amateur power levels the things
> should last for generations. I happen to like both the 3CX3000 and the
> 4CX3000A7 as well. The 3CX3000A7 operates at reasonable voltages, is
> rebuildable, and is capable of substantial output power at good IM
> products as is the 4CX3000A7. OTOH the sockets for the 3CX3000 are
> cheaper and currently readily available. The sockets for the 4CX3000
> are *EXPENSIVE*! which is probably why the tubes are available at pretty
> reasonable prices. BTW the 3 and 4CX3000 tubes are Thoriated Tungsten
> which makes them almost instant on. The 4CX version is rated full power
> to 150 MHz.
>
> Guess that covers far more than the original question.
>
> 73
>
> Roger (K8RI)
>> 73!Hsu
>
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