>Rich,
>
> Quite a convincing and unsolicited testimony. It has probably been a
>long time in coming but I see that you have not waivered in your stand.
The evidence speaks for itself. Eimac has not wavered from the
conclusion that an "oscillation condition" causes gold evaporation from
the grid of an 8877. I still wonder why Eimac's Reid Brandon told *QST*
that Eimac's chief specs engineer was not authorized to tell me about
gold evaporation in the 8877 ?
-- Eric didn't answer my question about your pal W8JI. I wonder wasup
with that ?
>
> You (still) have my admiration and respect.
>
** Thanks, Dave. Please say hello to aunt Veronica for me.
>
>Dave, WT8R, in Dayton - home of the Wright Brothers
>
To: <amps@contesting.com>
>Date: Tue, 4 Feb 2003 06:48:13 -0800 (PST)
>From: Joe Isabella <n3ji@yahoo.com>
>Subject: Re: [Amps] Re: Voodoo "EMF' forces from grid current pulses
>
>
>All,
>The "jumping cables" can also be seen if you've ever jump started a
>car. Watch what happens when the car with the "dead" battery is
>cranked. This is of course a substantial amount of instantanious
>current. Not knowing all the fancy laws, I can only go on empirical
>data. Jumper cables are huge compared to a tungsten filiment. The
>current to make a filiment move must be significantly less. I've never
>autopsied a tube and probably never will, but I **DO** know this: My
>TL-922 burned a bandswitch and arced on tune-up constantly (especially
>on 75m). Once I installed the mods recommended by Rich, this baby
>hasn't arced, spit, sputtered, or any other term you might be able to
>think of. The physics of a filiment-to-grid short may be "VooDoo" to
>me, but simple VHF oscillations and the stabilization/suppression mods
>aren't. And they worked.
>
>Joe,
>N3JI
>
>--- 2 <2@vc.net> wrote:
>>
>>
>> >I strongly challenge this assertion. I know of no mechanism within
>> the realm
>> >of classical EM field theory to account for this. I am assuming you
>> are
>> >referring to the normal force that would accompany two
>> current-carrying
>> >conductors which are in parallel proximity to each other.
>> >
>> Have you ever been to a welding shop and observed what happens to
>> arc-welder cables when an arc is struck? I have and I saw the cables
>>
>> jump about on the floor.
>>
>> >To illustrate the folly here, try the following numbers, which are
>> based
>> >upon
>> >basic physics ( see any good Intro E&M book - Kraus&Carver e.g.) I
>> >calculated the force (which itself is based upon the Lorenz force
>> which
>> >exists between a moving electron (a 'current') and a current
>> carrying
>> >conductor nearby.)
>> >
>> > I assumed 2 wires each 1" long and separated by 1mm, which I
>> believe would
>> >be representative of the grid-cathode geometry in a large
>> transmitting tube.
>> >With a current of 10 Amperes in each wire (which would no-doubt
>> vaporize any
>> >grid wire I ever saw)
>>
>> At its maximum ratings of 4000VDC and 250MHz, the grid in an 8877
>> quite
>> happily carries more than 42A-rms. Since there are 108 gold-plated
>> rectangular bars in the grid to share the current burden, under 0.4A
>> flows in each grid bar - so there is no heat problem. note -- The AC
>>
>> grid current results from the grid-anode C of 10pF and a potential of
>> c.
>> 2650V-rms at the anode. However, AC grid-current does not exert a
>> net
>> force on the grid.
>>
>> >the attractive force between the two wires is a
>> >whopping .0005N (multiply X ,22 for pounds). I don't think that is
>> going to
>> >be bending any wires. And that was assuming the ridiculous value of
>> 10A. for
>> >the current pulse, which I am assuming is quais-DC.
>>
>> Yes
>>
>> >If it is an AC field,
>> >especially at RF, the force would also oscillate with no net
>> (average)
>> >force.
>> >
>> Agreed
>>
>> >So if you want us the believe that the voodoo parasitics
>>
>> "Voodoo parasitics" is a term brandished by W8JI. Do you perhaps
>> know
>> him?
>>
>> >cause a current
>> >flow which generates a strong enough lateral force to damage the
>> wires,
>>
>> The grid wires in all of the shorted 3-500Z and 3-400Z tubes that I
>> have
>> autopsied appear to be straight. I have never seen a bent grid. The
>>
>> bent element is the thoriated-tungsten filament helix.
>>
>> >you will have to come up with another mechanism, one that can
>> generate some
>> REAL
>> >force.
>> >
>> There is no doubt that real force did the bending because real force
>> is
>> required to bend a bent filament straight. It typically takes 11-G
>> for
>> c. 40-seconds, with the filament operating at c. 5.6V, to straighten
>> the
>> filament.
>> - Eric -- How do you explain:
>> 1. the grid-filament short often seen in 3-500Zs often follows a
>> big-bang?
>> 2. the simultaneous burnout of a grid choke made from 28ga Cu wire?
>>
>> - R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
>> www.vcnet.com/measures.
>> end
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
>
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>
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
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