Ian White G3SEK wrote:
>For a ready made amp you can go to Henry, or you can go to a number of
>hams who build amps for sale, For example (K1FO -
>www.lunarlink.com). These generally use 3CX800s at 2-2.2kV and 70W
>drive is plenty for 1 KW output. A single 3CX800 will give 750W or 1kW
>if you push it, so good amps like lunarlink use two.
Point of clarification. The 3CX-800A7 has maximum rated operating
frequency of 350 Mhz. This tube is not suitable for use at 432 MHz. K1FO
uses the Eimac 3cPx-800A7 for his equipment above 220Mhz.
Stephen (K1FO) also points out that Svetlana only manufactures the
3CPX-800A7 but stamps 3CX-800A7 or 3CPX800A7 on the side of their tube
depending on what you order. Lunarlink products will use either tube and
present the option to the purchaser of the brand of tube they wish to
select. Lunarlink also urges their customers to purchase replacement tubes
through them as they are pretested. This would indicate that he is aware of
the fact that he is tickling the limits of these tubes.
If one is building their own amp the GS-35b is a much better tube as it is
rated clear to 1 Ghz. If the drive requirements of that tube are too steep
the GS-23b Tetrode is another option. Like the 35 it is also rated to 1 Ghz
and Grid Driven with a Screen Supply will produce 1500 Out with 20 watts of
drive.
73s
K1TA
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