Rich Measures wrote:
>
>>Back to the original question, then: exactly what produced the
>>mechanical force that made the filaments move?
>>
>This is still somewhat puzzling to me Ian. The peak grid current during
>the 110MHz oscillation is sufficient to melt the copper wire in the grid
>RFC.
I'm still using the neutral term "during the event".
> . According to the fusing current ratings of copper wire, the
>current (and the resulting electromagnetic force) must be substantial.
>The tungsten wire is fairly hot. Apparently, the electromagnetic force
>is strong enough to bend the hot wire.
>
Now can you take it down to the next level of detail, please:
what currents flow in which wires, in which directions, and how do they
produce the force that bends the wires?
Bear in mind that a valid explanation has to cover all three of the
following points:
1. According to the photographs, it's the heater wire that moves, not
the grid.
2. Currents in wires can produce their own magnetic field, but you have
to consider ALL the relevant wires.
3. RF current cannot bend the wire - above a few kHz it's too fast for
the wire to follow. To produce a net physical movement there has to be a
net DC component (or a low-frequency transient).
Sorry, I don't know what the right answer is - only the conditions that
it must meet.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
www.ifwtech.demon.co.uk/g3sek
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