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Re: An Important Post.
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Wednesday, August 06, 1997 10:41 PM
To: tesla-at-pupman-dot-com
Subject: Re: An Important Post.
Hi Julian,
> From: Julian Green[SMTP:julian-at-kbss.bt.co.uk]
> Sent: Tuesday, August 05, 1997 11:27 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: An Important Post.
>
> 1.6mH 800uH 400uH 200uH 100uH 50uH 25uH
> ----oooo--+--oooo--+--oooo--+--oooo--+--oooo--+--oooo--+--oooo--+---
> In | | | | | | | Out
> --- --- --- --- --- --- ---
> --- --- --- --- --- --- ---
> Gnd | | | | | | |
> ----------+--------+--------+--------+--------+--------+--------+---
> 10pF 22pF 50pF 100pF 220pF 470pF 1000pF
>
> Malcolm,
>
> Why are the values of the inductors and caps different? Surely the
> inductance of each unit length of a resonator coil is equal, same for
> the capacitance. Except for the top where the toroid normaly sits.
>
> Why not this?
>
> 25uH 25uH 25uH 25uH 25uH 25uH 25uH
> ----oooo--+--oooo--+--oooo--+--oooo--+--oooo--+--oooo--+--oooo--+---
> In | | | | | | | Out
> --- --- --- --- --- --- ---
> --- --- --- --- --- --- ---
> Gnd | | | | | | |
> ----------+--------+--------+--------+--------+--------+--------+---
> 10pF 10pF 10pF 10pF 10pF 10pF 1000pF
Simply because it doesn't agree with the calculations we use, most
notably the lumped L and C we successfully use to calculate Fr. If a
model doesn't agree with what we observe, it can't be correct. That
was the first one I tried. It is equivalent to a piece of coaxial
transmission line. BTW, the 1000pF you are using would drag F down
enormously. Typical toplads are around 5x Cself for the biggest ones
I've heard of being used and more usually, 1x or less. In fact, your
model might get close but a termination that big is not normally
used.
If in doubt, build one and measure it. I'd encourage everybody to
try it. I'm only one person. If someone comes up with something that
does agree with what we observe, it deserves the most thorough
consideration. The 1000pF on the end of my line was a result of
preserving the LxC grading constant at all sections. It wasn't a
topload as such.
Malcolm