[Amps] input matching question on the YC156?

[Harold B. Mandel]

Sirs,

One of the phenomena about amplifiers that concerns me is the
precipitation of VHF parasitic oscillations by transient-pulse type
events much akin to hitting a bell with a clapper. 

The proponents of making HV + and - along with Eg2 supplies
and leaving them on while in standby, coupled with K5PC's comments
on how overcurrent protection devices are better engineering seem to
be in line with avoiding the transient conditions that might precipitate
a destructive oscillation.

As well, the effect of relay contact bounce on the waveform of the
signal or voltage, in a very tiny amount of time, also lends itself to
the precipitation of bell-ringing, and with all this knowledge, does it
not make sense to limit or reduce the possible malfunctions that
multiple switching might inflect?

On one hand I want to protect an investment of thousands of
dollars in tubes. On the other hand I don't want that very
protection to be a possible source of damage.

Respectfully,

Hal Mandel
W4HBM



> > The plate and a screen voltage if needed was killed the same time 
> as the antenna relay opened. It was then applied as the antenna relay
> closed. But if you have the switching relays in parallel, etc and their

> switching time is the same, it will work, or has in what I've done. You
could 
> also have the antenna relay switch in and out another relay to apply
the B+
> and any screen if needed.  
> Will
> 
> I think there will be less dangerous solutions to prevent runaway of 
> a tube. Remember a floated cathode without ground connection keeps full
> anode voltage! To my knowledge no commercial communication transmitter
switches
> ht+ or screen voltage together with the t/r switch. Instead, they sense

>over- and undercurrent and disable transmit, or limit excessive current,
 
>to prevent damage to the tube  
> Peter