>
>Steve WB2WIK/6 writes --
>
>>Last time I built a tetrode amp I used a 4-1000A grid-driven and put +550V
>>on Ig2, provided by a stiff power supply that had no electronic regulation
>>whatever. Just a 400V, 200mA transformer, full-wave bridge, ~160uF
>>filtering, and a 10k, 50W bleeder resistor dissipating 30W. Eg2 never
>>varied by more than 1-2Vpk key up, key down, with modulation, without
>>modulation, whatever. Seemed plenty stiff enough to me, and cost about $20
>>for the entire circuit, including the transformer.
>
>One concern is that the smaller ceramic tubes (i.e. not "tetrodes with
>handles") are less forgiving than the 4-1000.
>
>Another concern is -- there's been a lot of "put up or shut up" catcalling,
>but the people calling the loudest really haven't provided any hard
>documentation on their "facts," other than a reference to the 50-year-old
>Eimac "Care and Feeding of Power Grid Tubes"
The original idea for shunt screen regulator for small tetrodes came from
an Eimac booklet titled "Single Sideband" c. 1955.
>and the information located on
>Mr. Measures' web site, which is easy to locate in any search engine, or
>via his standard email footer.
>
>John? Tom? URLs? Bibliographies?
>
>Personally, I'd like to see some different ways to control a screen before
>I start blowing stuff up over here. Tom, especially -- all of us know that
>it's damn near impossible for us to build an amp from new parts cheaper
>than you can.
The original Plywood Box cost me c. $1300 in parts. That works out to
<$92 per kW out the window.
>It's nearly as hard to build one out of surplus parts for as
>cheply as you sell 'em, once we're done building test fixtures and buying
>replacements for the stuff with a smoke leak.
>
>How about showing us how YOU do it?
>
>I'm still working on my broadband input transformer xperiment, and will
>post results as soon as they are available.
Great news. I was never able to build a (trifilar) 50? to 450? 150w
transformer that went from 160 - 10m. The latest rumour is that twisting
the wires works better.
cheers, Jim
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
end
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