Composite vs. Component Cables

Smarty wrote:
Matthew,

You ask me to "admit" that characteristic impedance is not important for
this specific connector and I can only say that this is true if the
connector is used in the manner for which it was originally intended,
namely, audio and low bandwidth composite video. If it is used
inappropriately for other applications, such as hi def TV, it very well may
be extremely important.

If the characteristic impedance of a short run video cable was
important, RCA connectors would not be used as they have no specified
characteristic impedance. A connector with a known impedance would be
used as they are in cable runs where characteristic impedance _is_
important.

Once again, RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. Please
do try.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

Matthew,

"RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. " is where
your head / thought process is stuck. You obviously have not understood
either the physical concept of impedance or the way in which it applies in
this specific instance.

Since you keep repeating the request for a citation from the web to
demonstrate that there actually is a characteristic impedance for RCA
connectors, then here is a link from Google which claims RCA connectors with
75 ohm characteristic impedance:
http://www.kingselectronics.com/News...5/Default.aspx


If you want a few more references claiming a 75 ohm RCA connector, I can
send them to you as well. Some 'manufacturers' are no more than marketing
and sales organizations which buy and assemble parts from the cheapest
sources available, make any claims they wish to make, and leave the consumer
asking legitimate questions about why and how these products perform as they
do.


You clearly have no interest in understanding this except at a very
superficial and incorrect level. You can continue to make statements that
RCA connectors have no characteristic impedance, and I will make no further
attempt to correct you.

Perhaps someone else reading this does now understand the basic
concept........each and every physical object can and does have a
"characteristic impedance", a physical phenomena which can be measured and
specified no different than length, width, weight, or other physical units.
In the case of impedance, it contains a resistive and a reactive term. Since
reactive (capacitive and inductive) impedance varies with frequency (one
goes up and the other goes down), the correct and only way to specify
impedance is as a function of frequency. A nominal (characteristic)
impedance can be substituted for the frequency range of interest to simplify
understanding. For RCA connectors, I promise you categorically (as will any
other electrical engineer like myself who has spent years in school learning
such things) that an RCA connector will not in any way remotely look like a
75 ohm impedance at any frequency near the range of interest in this
discussion. It is very easy for an advertising claim to be made for those
who lack understanding.

The essential and simple answer to the original poster has already been
stated, and my reply to ***your*** post was intended to correct your
incorrect statement. I believe I have achieved that, despite the confusion
your replies have added regarding "proof"' ' "admitting things", etc.


Smarty



"Matthew L. Martin" wrote in message
...
Smarty wrote:
Matthew,

You ask me to "admit" that characteristic impedance is not important for
this specific connector and I can only say that this is true if the
connector is used in the manner for which it was originally intended,
namely, audio and low bandwidth composite video. If it is used
inappropriately for other applications, such as hi def TV, it very well
may be extremely important.

If the characteristic impedance of a short run video cable was important,
RCA connectors would not be used as they have no specified characteristic
impedance. A connector with a known impedance would be used as they are in
cable runs where characteristic impedance _is_ important.

Once again, RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. Please do
try.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

Once again, RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. Please do
try.

I think everybody here is getting tired of your argument - I know I am, so I
decided to step in. There are actually countless manufacturers which provide
the impedance characteristics of their connectors. A simple Google search
yielded these results:
http://www.smarthome.com/7821cr.html
http://www.mouser.com/catalog/627/928.pdf

What are you going to say now? Please amuse me.

Or see section 3.5 of this article:
http://www.audioholics.com/techtips/...deocables4.php

Smarty explained it to you the best way one could, yet you won't concede the
point. Sad.

In article , Jim Gilliland
wrote:

Julian wrote:
In article , Jim Gilliland
wrote:

Julian wrote:
I had a discussion with a techie friend of mind, who claimed that there
was no PHYSICAL difference between a "composite" cable bundle and a
"component" bundle of three cables (i.e. the only difference being the
kind of signal that is sent down the wires). They are physically
interchangeable.

Is this correct?

The basic answer is NO, they are not equivalent. Component video requires
three 75 ohm cables. Composite video requires only one. There is no
requirement for the two audio cables in a composite bundle to be 75 ohm
cables, so you have to assume that they are not.

I'm not sure why we're seeing all the discussion about RCA connectors.
The
connectors aren't the issue. The characteristic impedance of the coax
itself
is what matters.

I'm also not sure why we're seeing any discussion of twisted pair. The
audio
cables in a composite bundle are coaxial cables. They're just not the
right
coaxial cables for video.

O.K. you guys. I now think I have the answer I was looking for. They
are basically the same (in a physical sense) except that "component"
cables are normally of a higher quality than "composite" cables, and
therefore (normally) command a somewhat higher price for an equivalent
length of cable.

If that's what you took from my post, then you've missed the point entirely.

As I said, the answer is NO, they are not equivalent. They are NOT the same
in
a physical sense. The difference is NOT just one of quality. They are
distinctly different cables, and even though they may look the same, they
behave
differently. They are not interchangeable.

In some circumstances, you may find that you can adequately pass video
through a
short length of audio cable. That doesn't make it the right cable for the
job,
and it's very likely causing some degree of degradation.

As another poster pointed out, some manufacturers may use video cable to
carry
audio. In that case, the audio cables will work fine for video (for obvious
reason). But without some sophisticated test equipment, you really have no way
of verifying that. So even in this case, you can't safely make that assumption.

O.K. Jim. I get the point (especially after the heated discussions
above). Thanks

--
Posted via a free Usenet account from http://www.teranews.com

ZVR,

It is indeed sad that Matthew has his feet (and perhaps his head) firmly
planted in the ground, and I apologize for all of this repetition in trying
to convey the basic technical points to him. I am done on this topic, and
apologize to the rest of this newsgroup for my repeated and perhaps overly
detailed attempts to (unsuccessfully) explain all of this to him.

Again, my apologies.

Smarty


"ZVR" wrote in message
g.com...
Once again, RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. Please
do try.

I think everybody here is getting tired of your argument - I know I am, so
I decided to step in. There are actually countless manufacturers which
provide the impedance characteristics of their connectors. A simple Google
search yielded these results:
http://www.smarthome.com/7821cr.html
http://www.mouser.com/catalog/627/928.pdf

What are you going to say now? Please amuse me.

Or see section 3.5 of this article:
http://www.audioholics.com/techtips/...deocables4.php

Smarty explained it to you the best way one could, yet you won't concede
the point. Sad.

Smarty wrote:
Matthew,

"RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. "
is where
your head / thought process is stuck. You obviously have not
understood
either the physical concept of impedance or the way in which it
applies in
this specific instance.

Since you keep repeating the request for a citation from the web to
demonstrate that there actually is a characteristic impedance for
RCA
connectors, then here is a link from Google which claims RCA
connectors with
75 ohm characteristic impedance:

http://www.kingselectronics.com/News...5/Default.aspx


If you want a few more references claiming a 75 ohm RCA connector, I
can
send them to you as well. Some 'manufacturers' are no more than
marketing
and sales organizations which buy and assemble parts from the
cheapest
sources available, make any claims they wish to make, and leave the
consumer
asking legitimate questions about why and how these products perform
as they
do.


You clearly have no interest in understanding this except at a very
superficial and incorrect level. You can continue to make statements
that
RCA connectors have no characteristic impedance, and I will make no
further
attempt to correct you.

Perhaps someone else reading this does now understand the basic
concept........each and every physical object can and does have a
"characteristic impedance", a physical phenomena which can be
measured and
specified no different than length, width, weight, or other physical
units.
In the case of impedance, it contains a resistive and a reactive
term. Since
reactive (capacitive and inductive) impedance varies with frequency
(one
goes up and the other goes down), the correct and only way to
specify
impedance is as a function of frequency. A nominal (characteristic)
impedance can be substituted for the frequency range of interest to
simplify
understanding. For RCA connectors, I promise you categorically (as
will any
other electrical engineer like myself who has spent years in school
learning
such things) that an RCA connector will not in any way remotely look
like a
75 ohm impedance at any frequency near the range of interest in this

discussion. It is very easy for an advertising claim to be made for
those
who lack understanding.

The essential and simple answer to the original poster has already
been
stated, and my reply to ***your*** post was intended to correct your

incorrect statement. I believe I have achieved that, despite the
confusion
your replies have added regarding "proof"' ' "admitting things",
etc.


Smarty

Your understanding appears to be more in the theoretical than real
realm. Granted, an RCA connector is not a 75 ohm connector, if its such
a problem, why are they used on nearly all consumer video units?
Answer: it has very little inpact on the performance for 1 or 2
connectors. Whoever said an RCA connectors impedance in 10's of megohms
is also WAY off the mark. No, I DON'T know what it is but I surely know
what it isn't.

BNC connctors used to be 50 ohm, not 75, until it became an issue with
135 MHz serial digital video. The 50 ohm connectors were used for many
years in broadcast. So mis-matches were common on baseband video and
not terribly troublesome.

The question was about component/composite cables. The audio cables are
rarely if ever 75 ohm cable and is to be avoided for video though 75
ohm cable is OK for the analog audio. The component cables should all
be 75 ohm and the same length and TYPE as not all 75 ohm cable has the
same transmission velocity. If you can measure the velocity and adjust
the lengths so all the signals stay 'in time' you could mix cable
types with no problems.

GG

Is it really the connector that has a natural impedance--or is it the cable
itself with a natural capacitance (reactance)?

--
All the Best
Richard Harison
"G-squared" wrote in message
ups.com...
Smarty wrote:
Matthew,

"RCA connectors have no specified, guaranteed, characteristic
impedance, unless, of course, you can find such a specification. "
is where
your head / thought process is stuck. You obviously have not
understood
either the physical concept of impedance or the way in which it
applies in
this specific instance.

Since you keep repeating the request for a citation from the web to
demonstrate that there actually is a characteristic impedance for
RCA
connectors, then here is a link from Google which claims RCA
connectors with
75 ohm characteristic impedance:

http://www.kingselectronics.com/News...5/Default.aspx


If you want a few more references claiming a 75 ohm RCA connector, I
can
send them to you as well. Some 'manufacturers' are no more than
marketing
and sales organizations which buy and assemble parts from the
cheapest
sources available, make any claims they wish to make, and leave the
consumer
asking legitimate questions about why and how these products perform
as they
do.


You clearly have no interest in understanding this except at a very
superficial and incorrect level. You can continue to make statements
that
RCA connectors have no characteristic impedance, and I will make no
further
attempt to correct you.

Perhaps someone else reading this does now understand the basic
concept........each and every physical object can and does have a
"characteristic impedance", a physical phenomena which can be
measured and
specified no different than length, width, weight, or other physical
units.
In the case of impedance, it contains a resistive and a reactive
term. Since
reactive (capacitive and inductive) impedance varies with frequency
(one
goes up and the other goes down), the correct and only way to
specify
impedance is as a function of frequency. A nominal (characteristic)
impedance can be substituted for the frequency range of interest to
simplify
understanding. For RCA connectors, I promise you categorically (as
will any
other electrical engineer like myself who has spent years in school
learning
such things) that an RCA connector will not in any way remotely look
like a
75 ohm impedance at any frequency near the range of interest in this

discussion. It is very easy for an advertising claim to be made for
those
who lack understanding.

The essential and simple answer to the original poster has already
been
stated, and my reply to ***your*** post was intended to correct your

incorrect statement. I believe I have achieved that, despite the
confusion
your replies have added regarding "proof"' ' "admitting things",
etc.


Smarty

Your understanding appears to be more in the theoretical than real
realm. Granted, an RCA connector is not a 75 ohm connector, if its such
a problem, why are they used on nearly all consumer video units?
Answer: it has very little inpact on the performance for 1 or 2
connectors. Whoever said an RCA connectors impedance in 10's of megohms
is also WAY off the mark. No, I DON'T know what it is but I surely know
what it isn't.

BNC connctors used to be 50 ohm, not 75, until it became an issue with
135 MHz serial digital video. The 50 ohm connectors were used for many
years in broadcast. So mis-matches were common on baseband video and
not terribly troublesome.

The question was about component/composite cables. The audio cables are
rarely if ever 75 ohm cable and is to be avoided for video though 75
ohm cable is OK for the analog audio. The component cables should all
be 75 ohm and the same length and TYPE as not all 75 ohm cable has the
same transmission velocity. If you can measure the velocity and adjust
the lengths so all the signals stay 'in time' you could mix cable
types with no problems.

GG




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http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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Smarty wrote:
ZVR,


To bad neither of you got the original poster's question. The use of
coax for one and two meter lengths of video/audio cable is for
shielding, not for impedance.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the game

Richard Harison wrote:
Is it really the connector that has a natural impedance--or is it the cable
itself with a natural capacitance (reactance)?

snip

Your understanding appears to be more in the theoretical than real
realm. Granted, an RCA connector is not a 75 ohm connector, if its such
a problem, why are they used on nearly all consumer video units?
Answer: it has very little inpact on the performance for 1 or 2
connectors. Whoever said an RCA connectors impedance in 10's of megohms
is also WAY off the mark. No, I DON'T know what it is but I surely know
what it isn't.

BNC connctors used to be 50 ohm, not 75, until it became an issue with
135 MHz serial digital video. The 50 ohm connectors were used for many
years in broadcast. So mis-matches were common on baseband video and
not terribly troublesome.

The question was about component/composite cables. The audio cables are
rarely if ever 75 ohm cable and is to be avoided for video though 75
ohm cable is OK for the analog audio. The component cables should all
be 75 ohm and the same length and TYPE as not all 75 ohm cable has the
same transmission velocity. If you can measure the velocity and adjust
the lengths so all the signals stay 'in time' you could mix cable
types with no problems.

GG



The inductance and capacitance is continuously distributed along the
length of the cable. The 'impedance' is where the reactive components
effectively cancel and it becomes resistive. The connector is only a
tiny part of the cable and just puts a 'bump' in the electical road
which is why you can get away with a less than perfect connector
particularly at the low frequencies of baseband video. The improper
impedance of the connector causes a small reflection in the cable i.e.
the VSWR is no longer 1. Signal-wise, it's identical to multipath. In
baseband analog video it shows up as smearing or ringing of the
transition depending on the severity of the reflection.

GG

Matthew L. Martin wrote:
Smarty wrote:
ZVR,


To bad neither of you got the original poster's question. The use of

coax for one and two meter lengths of video/audio cable is for
shielding, not for impedance.

Matthew

--
Thermodynamics and/or Golf for dummies: There is a game
You can't win
You can't break even
You can't get out of the
game

I used to think that too until I ran into an impedance mismatch on a
short 18" cable. Actually what Sony did inside the monitor was put the
terminator at the back panel with an 18" pigtail into the PCB. Changing
the 18" cable to transmission line and putting the terminator at the
end cleaned up the ringing in the video.

GG