[Milsurplus] BC-474 note

[Hubert Miller]

Many years ago, when Lincoln was still president, i repaired and tried out a BC-474. It suffered "fringe howl",
and to solve that, i connected a damping resistor across the output transformer primary. Now today i read C1
to TM 11-250, and it sez to "ground pin 1 of VT-148 socket to chassis, using shortest possible connection. This
will result in the tube shield being grounded through its clip..."

Now how did i miss that in 1985 ?
BTW, i don't think i have ever read a completely convincing explanation of "fringe howl". Someone on the old
Regenrx email group stated it was due to negative resistance in a regenerative stage, but it seems to me it has
something to do with capacitive feedback and the Q of an inductive output device.
-Hue Miller
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20230522/472383a8/attachment.html>