[ARC5] Transmiitters: Parameters?

[Mike Morrow]

Dennis wrote:

> The configuration as manufactured  produced the required output power
> and two tubes would provide a measure of increased reliability (and
> peace of mind as well...).

Two PA tubes in parallel provide little to nothing in advantages for reliability.  A mechanical element failure within either tube will almost certainly result in complete stage failure, short of simple connection loss at the base.  Likewise, the most common tube failure is an open filament.  The series-connected PA tube filaments then produce total PA stage failure.  Envelope failure in one tube with total vacuum loss will result in filament failure as well.  Thus, any argument of redundancy fails any postulated probable individual tube failure,

An argument for the two-tube design could be made based on two tubes performing as one larger tube.  At the desired design PA stage power, that would reduce long-duration stress by reducing plate and envelope temperatures and prolonging cathode emission lifetime, compared to a one-tube design.





DD
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On Mar 23, 2016, at 9:08 PM, Leslie Smith <vk2bcu at operamail.com> wrote:
 I don't understand your last sentence - and I think "whine" is a typo.  Maybe you meant "while it" or "when" or "will".  Also,  I don't follow the idea that "... the oscillator provides JUST enough drive for a SINGLE 1625 ...".  Clearly whoever designed this set - whether Dr. Drake or another technical (military) type  - "knew his knitting".   Why only JUST enough for a SINGLE 1625?   What's going on here?
     73 de Les Smith