[Amps] Russian tubes GS35b et al.

[Ian White, G3SEK]

K8LV wrote:
>I am looking for information on some of these Russian ceramic power tubes
>which are becomming so plentiful. However, in trying to do an actual design
>using the sparse data which I have obtained, I am getting very great
>discrepancies which I believe are due to errors in the data. They could also
>be a result of translation errors .
>
It seems to be mostly that the published curves don't extend into the 
areas you need to draw useful load lines, or to prepare a data file for 
KD9JQ's analysis program.

>I wonder if anybody has actually gone through a proper analysis of an
>amplifier design using the Russian data sheets, and gotten the right results?
>I know that many have built amps and tweaked their way to happiness, which is
>okay if thats the best you can do.
>
You can make quite good estimates of the optimum load impedance without 
needing any curves. If I remember correctly, 2000 ohms is a pretty good 
design figure, and about 50 ohms for the cathode drive impedance (in 
parallel with the tube capacitance).

>I would like to know the truth about these tubes, particularly the GS35B,
>which at first glance looks like the bargain of the year. But when I analyze
>it using the plate curves which I got from that LY2 guy, it only puts out
>about 600W max. With that big 1600W copper anode radiator?
>
At about 3.5kV, you get a very comfortable 1.5kW output up to 432MHz.

As G8GSQ said last week, "It's a tractor of a tube." Whiskery old 
Russian peasants beat out the anode coolers by hand, while their wives 
knitted the grids from recycled chicken wire.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek