75 Ohms - It's Not Just For TV Anymore
 

75 Ohms - It's Not Just For TV Anymore
-by- Don Irving

http://www.soundcityusa.net/vintage-...impedance.html

* The 'assertion' in this Article is that 50-Ohm
Antenna Hardware is often not the best choice.

? What is the "Ohms" Measurement associated
with Antenna Impedance ?

iane ~ RHF

75 Ohms - It's Not Just For TV Anymore
 

RHF wrote:

? What is the "Ohms" Measurement associated
with Antenna Impedance ?

Impedance, or 'Z' is measured in ohms.

The whole subject is a rather slippery slope and that's why 'Z' is
located on hypotenuse of the impedance triangle.

Awaiting your reactance,


sohcahtoa mike





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75 Ohms - It's Not Just For TV Anymore
 

On Thu, 14 Aug 2008 11:07:23 -0700, RHF wrote:


? What is the "Ohms" Measurement associated with Antenna Impedance ?

A ratio between the inner diameter of the outer conductor and the outer
diameter of the inner conductor.

75 Ohms - It's Not Just For TV Anymore
 

Dave wrote:

On Thu, 14 Aug 2008 11:07:23 -0700, RHF wrote:


? What is the "Ohms" Measurement associated with Antenna Impedance ?

A ratio between the inner diameter of the outer conductor and the outer
diameter of the inner conductor.


I've tried manipulating my twin lead cable into that configuration, to
no avail. The best I can get is something resembling a double helix. If
I leave it twisted like that, it may have genetic ramifications.



mike


--
__ __ __ __ __ __ __ __
/ /\ / /\ / /\ / /\ / /\ / /\ / /\ / /
/ /\ \/ /\ \/This space for rent/\ \/ /\ \/ /
/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/

Densa International©
'Think tanks cleaned cheap'

Due to the insane amount of spam and garbage,
I block all postings with a Gmail, Google Mail,
Google Groups or HOTMAIL address.
I also filter everything from a .cn server.

http://improve-usenet.org/

Parallel Feed-in-Lines Twin-Lead & Ladder-Line : To Twist ? -or- NotTo Twist ?
 

On Aug 14, 1:24*pm, m II wrote:
Dave wrote:
On Thu, 14 Aug 2008 11:07:23 -0700, RHF wrote:

? What is the "Ohms" Measurement associated with Antenna Impedance ?

A ratio between the inner diameter of the outer conductor and the outer
diameter of the inner conductor.

I've tried manipulating my twin lead cable into that configuration, to
no avail. The best I can get is something resembling a double helix. If
I leave it twisted like that, it may have genetic ramifications.

mike

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* *__ * *__ * *__ * *__ * *__ * *__ * *__ * *__
* / /\ */ /\ */ /\ */ /\ */ /\ */ /\ */ /\ */ /
*/ /\ \/ /\ \/This space for rent/\ \/ /\ \/ /
/_/ *\/_/ *\/_/ *\/_/ *\/_/ *\/_/ *\/_/ *\/_/

* * * * * * * *Densa International©
* * * * * *'Think tanks cleaned cheap'

* *Due to the insane amount of spam and garbage,
* *I block all postings with a Gmail, Google Mail,
* *Google Groups or HOTMAIL address.
* *I also filter everything from a .cn server.

* * * * * *http://improve-usenet.org/

Parallel Feed-in-Lines Twin-Lead & Ladder-Line :
To Twist ? -or- Not To Twist ?

The 'classic' 300 Ohm [TV type] Twin-Lead is 300 Ohms
whether it is Flat {un-twisted} -or- Twisted {Spiraled}.

The "Twisting" of the Pair {Twin} of Wires is supposedly
done to improve the 'local' Noise cancelling properties
from all directions of the Pair of {Parallel} Wires.

Question : For RF uses in the Shortwave Band 3 MHz
to 30 MHz : What is the 'typical' Ohmic Impedance of
common Speaker Wire {Zip Cord} ?

i want to know -cause- iane ~ RHF

75 Ohms - It's Not Just For TV Anymore
 

On Thu, 14 Aug 2008 20:24:01 +0000, m II wrote:

Dave wrote:

On Thu, 14 Aug 2008 11:07:23 -0700, RHF wrote:


? What is the "Ohms" Measurement associated with Antenna Impedance ?

A ratio between the inner diameter of the outer conductor and the outer
diameter of the inner conductor.


I've tried manipulating my twin lead cable into that configuration, to
no avail. The best I can get is something resembling a double helix. If
I leave it twisted like that, it may have genetic ramifications.

For parallel lines it's diameter v distance. Common zip cord is ca. 75
Ohms.

75 Ohms - It's Not Just For TV Anymore
 

Dave wrote:

I've tried manipulating my twin lead cable into that configuration, to
no avail. The best I can get is something resembling a double helix. If
I leave it twisted like that, it may have genetic ramifications.

For parallel lines it's diameter v distance. Common zip cord is ca. 75
Ohms.

Now, I've always been led to believe that a ratio is a unit less
quantity. I get the feeling that some length of cable is needed here to
get an ohmic value. Perhaps something approaching infinity?


mike (easy as falling off a Log) II



--
__ __ __ __ __ __ __ __
/ /\ / /\ / /\ / /\ / /\ / /\ / /\ / /
/ /\ \/ /\ \/This space for rent/\ \/ /\ \/ /
/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/

Densa International©
'Think tanks cleaned cheap'

Due to the insane amount of spam and garbage,
I block all postings with a Gmail, Google Mail,
Google Groups or HOTMAIL address.
I also filter everything from a .cn server.

http://improve-usenet.org/

75 Ohms - It's Not Just For TV Anymore
 

On Thu, 14 Aug 2008 22:13:34 +0000, m II wrote:

Dave wrote:

I've tried manipulating my twin lead cable into that configuration, to
no avail. The best I can get is something resembling a double helix.
If I leave it twisted like that, it may have genetic ramifications.

For parallel lines it's diameter v distance. Common zip cord is ca. 75
Ohms.

Now, I've always been led to believe that a ratio is a unit less
quantity. I get the feeling that some length of cable is needed here to
get an ohmic value. Perhaps something approaching infinity?

Characteristic Z assumes infinite length.
mike (easy as falling off a Log) II

75 Ohms - It's Not Just For TV Anymore
 

On Thu, 14 Aug 2008 22:13:34 +0000, m II wrote:

Now, I've always been led to believe that a ratio is a unit less
quantity. I get the feeling that some length of cable is needed here to
get an ohmic value. Perhaps something approaching infinity?


http://www.allaboutcircuits.com/vol_2/chpt_14/3.html

75 Ohms - It's Not Just For TV Anymore
 

"m II" wrote in message news:i62pk.7114$%b7.6611@edtnps82...
Dave wrote:

I've tried manipulating my twin lead cable into that configuration, to
no avail. The best I can get is something resembling a double helix. If
I leave it twisted like that, it may have genetic ramifications.

For parallel lines it's diameter v distance. Common zip cord is ca. 75
Ohms.

Now, I've always been led to believe that a ratio is a unit less
quantity. I get the feeling that some length of cable is needed here to
get an ohmic value. Perhaps something approaching infinity?


mike (easy as falling off a Log) II


Don't confuse DC Ohms with surge impedance of coaxial line- they have
nothing in common except their unit of measurement.
Speaker wire probably is a relatively low Z line- which then suffers from
two issues:

1.One reason typical amateur balanced line is low loss is because of the
high impedance.
2. The vinyl insulation of typical speaker wire is a lossy dielectric
compared to the polyethylene of balanced transmission lines. Look at the
tangent angle of vinyl vs. polyethylene or teflon.

Dale W4OP