>
>Eimac and Svetlana, has J series for their tetrodes, from the the data
>sheets it claims an imrpvement in 3rd
>order imd, does anyone know how much the 3rd order IMD is improved over the
>conventional bottle? It seems these tetrodes are driven with higher screen
>and grid voltages.
>
The critical moment of truth for a tetrode is the instant when the grid
is near the peak in signal voltage -- i.e., as the grid potential is
nearing Zero volts. If emission falters hereabouts, distortion results.
The J series of tetrodes have more emission reserve than their ordinary
cousins. For instance, a 4cx10,000J has a 104a fil., and the
4cx10,000D/8171 has a 75A fil. Even though the max. current rating is 4A
avg. for either tube, the extra reserve of emission in the J version
provides better linearity in the region of the critical peak. The major
consideration in switching from a plain-vanilla version to a J version is
the capability of the fil. trans. . The relative improvement in IMD with
a J version appears to be in the 4 to 6 db range. The 4cx10,000J has a
3rd order rating of minus 41db below pep.
- later, Craig
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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