"Reg Edwards" wrote in message
...
Zo of ALL real, ordinary, transmission lines changes versus frequency over
a
very wide frequency range.

Zo ranges over lots of thousands of ohms at a few cyles of seconds,
thousands of ohms at power frequencies, hundreds of ohms at audio
frequencies, and from tens to a few hundred ohms from 100KHz up to as many
GHz as you like.
---
Reg.



Are we talking the same thing for Zo ? That a piece of say rg-8 ( whatever
they want to call it now) that is 50 ohm coax is not 50 ohms over its normal
operating frequency range ?

"Reg Edwards" wrote in message
Zo of ALL real, ordinary, transmission lines changes versus frequency
over
a
very wide frequency range.

Zo ranges over lots of thousands of ohms at a few cyles of seconds,
thousands of ohms at power frequencies, hundreds of ohms at audio
frequencies, and from tens to a few hundred ohms from 100KHz up to as
many
GHz as you like.
---
Reg.



Are we talking the same thing for Zo ? That a piece of say rg-8 (
whatever
they want to call it now) that is 50 ohm coax is not 50 ohms over its
normal
operating frequency range ?

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

What is your normal operating frequency range?

Here is Zo typical of cable similar to RG-58 versus frequency.

Nominal Zo = 50 ohms.
Degrees = Angle of Zo.

Freq Zo Degrees
------ ------- -------
10 Hz 3000 -45.0
100 Hz 950 -44.9
1000 Hz 301 -44.1
10 KHz 97 -36.4
100 KHz 54.2 -10.1
1 MHz 50.0 -2.6
10 MHz 48.4 -0.84
100 MHz 48.0 -0.26
1 GHz 47.8 -0.08

Superimposed on the above Zo vs F characteristics are manufacturing
reel-to-reel variations of 2 or 3 percent.
----
Reg, G4FGQ

Someone sed about the characteristic frequency of a transmission line::

"It does not change at any reasonable frequency for the line. That is at
least anything below 1 ghz for coax."

The formula for Zo contains the frequency.

Look it up.

73 de Jack K9CUN

Someone sed:

" Do you know of anyone that has an infinite length of transmission line? Or
an infinite anything? :-)."

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

Some of these threads are PRETTY LONG, approaching infinity???

73 de Jack, K9CUN

Someone sed:

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

This is an *approximation* that is useful when complex arithmetic is over the
capability of your calculator or if the imaginary components of the formula for
Zo are negligible.

At the usual HF through UHF ham frequencies the imaginary components are
negligible so the approximation suffices.

UNITS: 10-pF capacitor. 10-pF is hypenated when used as a modifier, i. e.,
adjective.

Others: 10-ft pole, 5-cent cigar, 2-dollar pistol, 12-V battery, 500-mile
track.

73 de Jack, K9CUN

JDer8745 wrote:

snip


UNITS: 10-pF capacitor. 10-pF is hypenated when used as a modifier, i. e.,
adjective.

Others: 10-ft pole, 5-cent cigar, 2-dollar pistol, 12-V battery, 500-mile
track.

73 de Jack, K9CUN


Partly correct.

The use of "10-picofarad capacitor" is preferred under the standard rules of
English and the NIST style guide. The use of "10-pF capacitor" should be
replaced by "10 pF capacitor" according to NIST.

See section 7.2 in http://www.physics.nist.gov/Pubs/SP811/contents.html

"Even when the value of a quantity is used in an adjectival sense, a space is
left between the numerical value and the unit symbol. (This rule recognizes that
unit symbols are not like ordinary words or abbreviations but are mathematical
entities, and that the value of a quantity should be expressed in a way that is
as independent of language as possible.)"

"When unit names are spelled out, the normal rules of English apply. Thus, for
example, ‘a roll of 35-millimeter film’ is acceptable."

73,
Gene
W4SZ

When putting up an antenna, do you use different Zo coax for 2 Vs. 80 meters
to account for frequency change?

The Zo is constant for all practical purposes below Giga Hz freqs.

"JDer8745" wrote in message
...
Someone sed,

"Reg, G4FGQ observed on these pages long ago that an ordinary ohmmeter
would
read Zo if connected to the end of an infinite line. He is right of
course."

But the Zo of a line varies with frequency. How will the "ordinary
ohmmeter"
do the job at, say, 100 kHz?

73 de jack

As most of us do not transmit in the audio range, your own data shows a
range of 50 to 47.8 Ohms for normal ham use. Close enough for government
work, at least as far as I am concerned..

"Reg Edwards" wrote in message
...

"Reg Edwards" wrote in message
Zo of ALL real, ordinary, transmission lines changes versus frequency
over
a
very wide frequency range.

Zo ranges over lots of thousands of ohms at a few cyles of seconds,
thousands of ohms at power frequencies, hundreds of ohms at audio
frequencies, and from tens to a few hundred ohms from 100KHz up to as
many
GHz as you like.
---
Reg.



Are we talking the same thing for Zo ? That a piece of say rg-8 (
whatever
they want to call it now) that is 50 ohm coax is not 50 ohms over its
normal
operating frequency range ?

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

What is your normal operating frequency range?

Here is Zo typical of cable similar to RG-58 versus frequency.

Nominal Zo = 50 ohms.
Degrees = Angle of Zo.

Freq Zo Degrees
------ ------- -------
10 Hz 3000 -45.0
100 Hz 950 -44.9
1000 Hz 301 -44.1
10 KHz 97 -36.4
100 KHz 54.2 -10.1
1 MHz 50.0 -2.6
10 MHz 48.4 -0.84
100 MHz 48.0 -0.26
1 GHz 47.8 -0.08

Superimposed on the above Zo vs F characteristics are manufacturing
reel-to-reel variations of 2 or 3 percent.
----
Reg, G4FGQ

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


"JDer8745" wrote in message
...
Someone sed:

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

This is an *approximation* that is useful when complex arithmetic is over
the
capability of your calculator or if the imaginary components of the
formula for
Zo are negligible.

At the usual HF through UHF ham frequencies the imaginary components are
negligible so the approximation suffices.

UNITS: 10-pF capacitor. 10-pF is hypenated when used as a modifier, i.
e.,
adjective.

Others: 10-ft pole, 5-cent cigar, 2-dollar pistol, 12-V battery, 500-mile
track.

73 de Jack, K9CUN

"Reg Edwards" wrote in message
Zo of ALL real, ordinary, transmission lines changes versus frequency
over
a
very wide frequency range.

Zo ranges over lots of thousands of ohms at a few cyles of seconds,
thousands of ohms at power frequencies, hundreds of ohms at audio
frequencies, and from tens to a few hundred ohms from 100KHz up to as
many
GHz as you like.
---
Reg.



Are we talking the same thing for Zo ? That a piece of say rg-8 (
whatever
they want to call it now) that is 50 ohm coax is not 50 ohms over its
normal
operating frequency range ?

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

What is your normal operating frequency range?

Here is Zo typical of cable similar to RG-58 versus frequency.

Nominal Zo = 50 ohms.
Degrees = Angle of Zo.

Freq Zo Degrees
------ ------- -------
10 Hz 3000 -45.0
100 Hz 950 -44.9
1000 Hz 301 -44.1
10 KHz 97 -36.4
100 KHz 54.2 -10.1
1 MHz 50.0 -2.6
10 MHz 48.4 -0.84
100 MHz 48.0 -0.26
1 GHz 47.8 -0.08

Superimposed on the above Zo vs F characteristics are manufacturing
reel-to-reel variations of 2 or 3 percent.
----
Reg, G4FGQ


Think I must have missed the point about REAL transmission lines. Trying to
keep up with too many discussions at one time. I was thinking of the simple
formular where frequency is not mentioned. I do know about the problem of
making the coax exectally the same all the time where even in the same reel
of coax you can get into suckout problems due to slight variations in the
coax.