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Co-as cable: truth or nonsense?



 
 
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  #11  
Old November 10th 16, 10:27 AM posted to uk.tech.digital-tv
Chris Green
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Posts: 134
Default Co-as cable: truth or nonsense?

Jim Lesurf wrote:

As per Bill's original point. Gold has a slightly higher conductivity than
copper. So may give lower loss at low frequency. But the higher the
conductance, the thinner the 'skin' at HF. So the cross-section used for
conduction may be smaller. So you may not get the anticipated advantage at


No, the only metal which is a better conductor than copper is silver.
Gold is useful because it doesn't corrode so where surface effect is
involved (and for low current contacts) it is often better.

--
Chris Green
·
  #12  
Old November 10th 16, 01:16 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,138
Default Co-as cable: truth or nonsense?

In article , Chris Green
wrote:
Jim Lesurf wrote:

As per Bill's original point. Gold has a slightly higher conductivity
than copper. So may give lower loss at low frequency. But the higher
the conductance, the thinner the 'skin' at HF. So the cross-section
used for conduction may be smaller. So you may not get the anticipated
advantage at


No, the only metal which is a better conductor than copper is silver.
Gold is useful because it doesn't corrode so where surface effect is
involved (and for low current contacts) it is often better.


Sorry, yes, I'd forgotten the value for gold. Had to look up my own webpage
to check
https://www.st-andrews.ac.uk/~www_pa...rt7/page3.html

So on that basis gold might have a slightly advantageous skin depth.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #13  
Old November 10th 16, 06:04 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 420
Default Co-as cable: truth or nonsense?

On Thursday, 10 November 2016 01:16:52 UTC, wrote:
On 09/11/2016 20:24, R. Mark Clayton wrote:

A solid copper centre core as copper is better conductor of electricity
and signals than gold! So go for copper conductors. Aluminium is only 61%
as effective as copper.


By volume, but by weight it is better - and a quarter of the price - so just make thicker cores.


The ratio between the diameter of the inner and the outer sets the
characteristic impedance, so the whole cable would be thicker.


Yes, but lighter.

BT used a lot of cable with Al conductors back in the 70's, but it is c**p.

OTOH I think they use it for long spans on the national grid.



Bill


  #14  
Old November 10th 16, 09:44 PM posted to uk.tech.digital-tv
David Woolley[_2_]
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Posts: 514
Default Co-as cable: truth or nonsense?

On 10/11/16 08:50, Brian Gaff wrote:
I'd have thought that cctv signals if analogue were calssed as RF,


They will have significant energy at frequencies at which the
characteristic impedance of the line has not stabilised, and currents
are flowing quite deep in the conductors. Basically they are in an area
where coax is not well behaved.
  #15  
Old November 11th 16, 01:08 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 1,622
Default Co-as cable: truth or nonsense?

On 10/11/2016 22:44, David Woolley wrote:
On 10/11/16 08:50, Brian Gaff wrote:
I'd have thought that cctv signals if analogue were calssed as RF,


They will have significant energy at frequencies at which the
characteristic impedance of the line has not stabilised, and currents
are flowing quite deep in the conductors. Basically they are in an area
where coax is not well behaved.


Almost down to DC. Like a lot of other things it didn't orter work, but
it does.

Bill
  #16  
Old November 11th 16, 11:12 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,505
Default Co-as cable: truth or nonsense?

OK who bin messin wiv me space bar!
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Brian Gaff" wrote in message
news
I was always thought the all hf tends to travel on the outside, so plated
cables should be fine.

Often coax that would seem tto be inferior will actually work very well
while some great theoretically superior one won't make any discernable
difference for most uses.
Ido think there is a lot more to consider in such systems than the
conductor material and its plating. Matching and what occurs when you bend
it for example.

Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Bill Wright" wrote in message
...
Quotes from a recent CCTV trade flier:

Start quotes

A solid copper centre core as copper is better conductor of electricity
and signals than gold! So go for copper conductors. Aluminium is only 61%
as effective as copper.

Cheap cable such as CCA (Copper Clad Aluminium) and CCS (Copper Clad
Steel) - Cheaper but in reality a false economy. CCA is around 61%
effective as pure copper and CCS as low as 17% - In layman's terms; If a
copper cable works at 100m then the CCA would only work at 61m and the
CCS at just 17m !!

End quotes

Bear in mind that this is for CCTV, not RF. Since cable TV companies
often use steel cored coax for UHF I find the claims above surprising.

Bill





  #17  
Old November 11th 16, 05:36 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
external usenet poster
 
Posts: 420
Default Co-as cable: truth or nonsense?

On Thursday, 10 November 2016 08:48:02 UTC, Brian Gaff wrote:
I was always thought the all hf tends to travel on the outside, so plated
cables should be fine.

Often coax that would seem tto be inferior will actually work very well
while some great theoretically superior one won't make any discernable
difference for most uses.
Ido think there is a lot more to consider in such systems than the
conductor material and its plating. Matching and what occurs when you bend
it for example.

Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Bill Wright" wrote in message
...
Quotes from a recent CCTV trade flier:

Start quotes

A solid copper centre core as copper is better conductor of electricity
and signals than gold! So go for copper conductors. Aluminium is only 61%
as effective as copper.

Cheap cable such as CCA (Copper Clad Aluminium) and CCS (Copper Clad
Steel) - Cheaper but in reality a false economy. CCA is around 61%
effective as pure copper and CCS as low as 17% - In layman's terms; If a
copper cable works at 100m then the CCA would only work at 61m and the CCS
at just 17m !!

End quotes

Bear in mind that this is for CCTV, not RF. Since cable TV companies often
use steel cored coax for UHF I find the claims above surprising.

Bill


It is down to EMF (voltage) and is called skin effect.
  #18  
Old November 11th 16, 08:03 PM posted to uk.tech.digital-tv
Phi
external usenet poster
 
Posts: 238
Default Co-as cable: truth or nonsense?


"R. Mark Clayton" wrote in message
...
On Thursday, 10 November 2016 08:48:02 UTC, Brian Gaff wrote:
I was always thought the all hf tends to travel on the outside, so plated
cables should be fine.

Often coax that would seem tto be inferior will actually work very well
while some great theoretically superior one won't make any discernable
difference for most uses.
Ido think there is a lot more to consider in such systems than the
conductor material and its plating. Matching and what occurs when you
bend
it for example.

Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Bill Wright" wrote in message
...
Quotes from a recent CCTV trade flier:

Start quotes

A solid copper centre core as copper is better conductor of electricity
and signals than gold! So go for copper conductors. Aluminium is only
61%
as effective as copper.

Cheap cable such as CCA (Copper Clad Aluminium) and CCS (Copper Clad
Steel) - Cheaper but in reality a false economy. CCA is around 61%
effective as pure copper and CCS as low as 17% - In layman's terms; If
a
copper cable works at 100m then the CCA would only work at 61m and the
CCS
at just 17m !!

End quotes

Bear in mind that this is for CCTV, not RF. Since cable TV companies
often
use steel cored coax for UHF I find the claims above surprising.

Bill


It is down to EMF (voltage) and is called skin effect.



We used the skin effect of Inconel troughs to melt glass to stabilise
radioactive waste.

  #19  
Old November 24th 16, 01:32 PM posted to uk.tech.digital-tv
tony sayer
external usenet poster
 
Posts: 4,963
Default Co-as cable: truth or nonsense?

In article , Bill Wright
scribeth thus
On 09/11/2016 20:24, R. Mark Clayton wrote:

A solid copper centre core as copper is better conductor of electricity
and signals than gold! So go for copper conductors. Aluminium is only 61%
as effective as copper.


By volume, but by weight it is better - and a quarter of the price - so just

make thicker cores.

The ratio between the diameter of the inner and the outer sets the
characteristic impedance, so the whole cable would be thicker.

Bill


And the effect of skin effect?..
--
Tony Sayer




  #20  
Old November 24th 16, 03:42 PM posted to uk.tech.digital-tv
Phi
external usenet poster
 
Posts: 238
Default Co-as cable: truth or nonsense?


"tony sayer" wrote in message
...
In article , Bill Wright
scribeth thus
On 09/11/2016 20:24, R. Mark Clayton wrote:

A solid copper centre core as copper is better conductor of
electricity
and signals than gold! So go for copper conductors. Aluminium is only
61%
as effective as copper.

By volume, but by weight it is better - and a quarter of the price - so
just

make thicker cores.

The ratio between the diameter of the inner and the outer sets the
characteristic impedance, so the whole cable would be thicker.

Bill


And the effect of skin effect?..
--
Tony Sayer



Heat



 




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