[Amps] Parasitics & Filament Sag

[Tom W8JI]

> Here is what I understand from the consensus of opinion:
>
> 1. VHF Parasitics may develop sufficient amperage
>    such that filaments may physically distort.

That is electrically impossible. There is only so much 
emission available, and the force from even many dozens of 
amperes is in the order of grams.
It is nearly impossible from filament inrush, it is totally 
impossible from oscillations or even excessive RF drive 
power.

> 2. Some sort of oscillation can happen as a result
>    of mis-tuning, etc., that may be called "parasitic."

It might be called a parasitic, but it isn't. It also isn't 
an oscillation.

If you read this page you will see step by step what causes 
a mistuning or load fault arc:

http://www.w8ji.com/demonstation.htm


> 3. The Q of the Lsup device may or may not dampen
>     oscillations or events that may cause filament sag.\

Moot point since it is impossible for an oscillation to 
damage the filament, unless it is a mechanical oscillation 
like bouncing the tube off a wall.

> 4.  Some 8877 amps have used Lsup devices, some
>     have not.

True. Many do. Many do not.

> 5.  Some commercial manufacturers use Lsup
>     material(s) that are higher resistance than
>     silver strapping with no attempt at an added
>     series inductance.

What is an Lsup?

73 Tom