>
>Rich, see my questions below:
>
>----------
>From: measures[SMTP:2@vc.net]
>Sent: Sunday, March 05, 2000 3:11 PM
>To: Michael Tope; AMPS; 'W8JI@contesting.com'
>Subject: RE: [AMPS] Network analysis of suppressors
>
>>>
>>> Borrow a geiger counter, Mr. Rauch, and tune in on what's happening on the
>>> upper frequencies. Be not surprised if you occasionally encounter some
>>> humungous signals.
>>
>>Rich or Tom, please forgive me if I misrepresent any of your
>>claims as I haven't been following this debate very closely
>>and hence am not fully versed in the details of your respective
>>positions. Regarding the idea that radiation single events can
>>cause significant current to flow in a high power vacuum tube,
>>this seems unlikely to me.
>
>As it first did to me, Mike. My guess is that a photon strikes an atom,
>knocking loose a current carrier/electron, thereby causingthe tube to
>briefly conduct. This causes several kV to appear across the bias
>contacts, which arc. The contacts form a metal vapour arc. Since the
>voltage drop across such an arc is low, the amplifier tube switches out
>of cutoff bias and an event could take place.
>
>cheers
>
>Rich, a couple of questions?
>
>1. Are my assumptions about the operating conditions
>in the above scenario correct - B+ = ON, Filament = ON,
>BIAS = CUTOFF?
>
yes
>2. From where in the tube does the free carrier (electron)
>emanate - the surface of the cathode, the control grid,
>the anode, residual gas in tube?
>
no ideas. Gamma rays and secondary cosmic rays should be able to knock
electrons loose from any atom they collide with.
>3. What is the direction of the current flow that is created
>by the free carriers - cathode to grid, cathode to anode, grid
>to anode?
cathode to anode
>
>4. How do a few electrons create a potential change of several
>thousand volts across the bias relay contacts?
They don't. The supply is 3000v. Roughly 25v is dropped across the bias
contacts. Roughly 2975v is dropped across the cutoff tube. When the
tube conducts, the drop across the bias contacts increases (Thevenin).
The bias contacts arc. The low potential across the metal vapour arc at
the contacts biases the tube into conduction. This causes the anode
resonant circuit to produce damped-wave VHF ringing. If the tube has
sufficient feedback, oscillation is possible. Since the tank is a low
pass arrangement, the VHF energy produced during oscillation has no load,
so it runs amok.
> Since V = Q/C,
>seems like it would take many electrons to raise the voltage
>across the bias relay contacts to a few thousand volts (the
>charge on an electron is around 10E-19 coulombs). How many
>electrons are we talking? Is the bandgap energy involved in the
>carrier release consistent with radiation events of probable
>magnitude (or are we talking about real "big bang" energies?)
>
The electrons that are knocked loose in the collision do not make the big
bang. They knock over the first domino and Murphy's Law does the rest.
That's my guess.
.cheers, Mike.
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