| |
VK2ZRG > TECH 29.05.06 06:20l 45 Lines 1949 Bytes #999 (0) @ WW
BID : 15883_VK2WI
Read: DL1LCA GUEST
Subj: Re: Resistivity of Chromium
Path: DB0FHN<DB0RGB<DB0MRW<DB0ERF<DB0FBB<DB0IUZ<DB0GOS<DB0RES<DK0WUE<CE8FGC<
SV1CMG<VK6HGR<VK7AX<VK2TGB<VK2IO<VK2WI
Sent: 060529/0343Z @:VK2WI.#SYD.NSW.AUS.OC #:15883 [SYDNEY] FBB7 $:15883_VK2WI
From: VK2ZRG@VK2WI.#SYD.NSW.AUS.OC
To : TECH@WW
VK2ZRG/TPK 1.83d Msg #:2355 Date:29-05-06 Time:3:38Z
Hello Pete, Andy and readers,
Many thanks to Pete G6KUI, Andy GM7HUD and others who have contributed to
this subject. It seems that my gut feeling, that the resistance of chromium
given as 1.8 times that of copper in the ARRL Handbook was wrong, was right.
8.1 times would be more plausible. In all the years that I've been in the
electronics game, I've never heard chromium being mentioned as a low
resistance metal.
I don't believe everything in print, or on a computer screen, just because
the it is published by some reputable organisation. My 1990 ARRL UHF/Microwave
Experimenter's Manual has many errors in it. Not only in mathematical formulas
and such like, but also in text. I'll quote from the chapter on transmission
lines, talking about coaxial lines.
"And distributed capacitance should vary directly with the square root of
the permittivity of the dielectric, just as the capacitance of any capacitor
increases by a factor of four if the dielectric constant is doubled."
Well that is plainly wrong. I hope everyone knows that capacitance is
proportional to the dielectric constant. It was when I learnt about it, and
still is, unless the laws of physics have been changed.
As for computers and the web, I think that many people believe that anything
that appears on a computer screen must be right. Do they believe GIGO stands
for Garbage In Gospel Out?
Here's something to think about. If you make a simple calculation on a four
function pocket calculator, how do you know if the answer is wrong or right?
i.e. Did you press the right buttons?
Anyway, back to chromium, I think I'll use a value of 12.9 micro ohm-cm
for my programme. Should be near enough for most purposes.
73s from Ralph VK2ZRG@VK2WI.#SYD.NSW.AUS.OC
Taglines by Colin Coker G4FCN
C Program run, C Program Crash...ReWrite in Pascal!
Read previous mail | Read next mail
| |
