>
>Rich says;
>
>>However with ordinary tetrodes,, grid current is clearly to be avoided
>>unless one is either trying to clear away a wide swath during a contest,
>>or operating on CB Channel 6. .
>
>What do you mean by 'an ordinary tetrode'?
7580, 4-250A, 4CX1500A, 8169, 4-500A, 8171. .
> It seems strange to me that for
>many years, companies like Collins, Racal, Marconi, Standard Telephones,
>Brown Boveri, Thomson, Philips, Siemens etc have made tubes and transmitters
>to exacting professional specs (especially for ISB) and used AB2 operation.
Please name a (not G-G) Collins amplifier that used AB2 instead of AB1.
.
thanks
>But Rich says it doesn't work.
Rich says AB2 grid-driven works.
> Just because Eimac only happen to list two
>tubes for negligible grid current (as opposed to none at all), Rich says
>that Class AB2 produces splatter. Too much of a generalisation, Rich.
The constant current curves prove why this is generally the case. The
4-500A is an ordinary tetrode without the special dispenser cathode and
low-intercept grid that distinguishes the 8660/4CX1500B. . Unlike the
4CX1500B, the 4-500A's curves take a nasty turn when grid current is
present. Eimac recommends zero grid current for the 4-500A, 4CX1500A,
8169, 8170, 8171, 8281, 8349 and 8973. . Surely, one gets a bit more
peak anode current when the grid is positive, but the improvement on an
S-meter would be unnoticed.
>
later, Peter
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|