Ron -
The problem isn't so much harmonics as 3rd order distortion. Especially
if the final tubes are not particularly well matched, the cathode
resistors have changed value, etc.... The Finals are run at just about
the limit for "clean" SSB, i.e., 3rd order down at least >30 dB is the
spec I believe. FCC doesn't really give a spec, just "best amateur
practice" or somesuch. The more tubes in parallel, the more things to
go wrong! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Ron wrote:
I've often wondered why the TR series (with 3 finals) is only allowed 10 more
milliamps of final plate current than the twins (with 2 tubes). That being 350
vs 340. Is it that multiple tubes in parallel are by their nature more prone
to distortion and therefore harmonics? Ideas?
If you are unaware, see this link.
http://wb4hfn.com/DRAKE/DrakeArticles/TransmittingTuningAlt.htm
73,
Ron WD8SBB
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