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-   -   the "300/75/50 ohms" of TV ribbon, coax (https://www.radiobanter.com/antenna/875-%22300-75-50-ohms%22-tv-ribbon-coax.html)

Irv Finkleman December 11th 03 11:19 PM

w4jle wrote:

Jack, with all due respect, you need a hobby...



He was just getting his 2-cents worth in! :-)
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
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Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Andy Cowley December 12th 03 02:49 PM

Reg Edwards wrote:

Ohm is a name of a person.

=======================

During which era did Mr Inch live?


Wasn't he at Cambridge with Furlong,
Yard, Chain and a Polish guy called
Rod Perch? I think that was the group
that first discovered length, or was
it distance? ;-)

(Actually derived from Latin, uncia, an ounce.)

In fact the SI units don't have a fixed rule for
capitalisation. When the unit is spelt out it should
not be capitalised - ohm, kelvin, farad - to avoid
confusion with the scientist. The abbreviation or
symbol should be capitalised for all those named
after people and for litre - Hz, L, V. The ohm is
normally written with a capital omega or written
in full as 'ohm'. Ohm at the beginning of a sentence
is capitalised.

See http://www.poynton.com/PDFs/Writing_SI_units_(USL).pdf

vy 73

Andy, M1EBV

JDer8745 December 12th 03 10:43 PM

Someone sed:

"So, the 300/75/50 ohm term, characteristic impedance, is the square root of
L/C"
==================

Not always!

73 de Jack, K9CUN

Dave Shrader December 13th 03 01:04 PM

To a first approximation ... YES. In the context of providing a simple
explanation, an introductory level explanation, as in the context of the
original question ... YES.

In the interest of more advanced analysis:

Zo = SQRT[[R + jwL]/[G + jwC]]

In a lossless line that converges to SQRT [L/C].

DD

JDer8745 wrote:

Someone sed:

"So, the 300/75/50 ohm term, characteristic impedance, is the square root of
L/C"
==================

Not always!

73 de Jack, K9CUN



JDer8745 December 13th 03 02:54 PM

"In a lossless line that converges to SQRT [L/C]."

There is no such thing as a lossless line. The formula becomes SQRT(L/C) as
the frequency increases, but the losses don't go away. In fact losses of TLs
increase as frequency increases. Nice graphs of this in the Handbook.

73 de jack, K9CUN


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