The truth about decibels

[Adrian Tuddenham]

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:

Kevin Aylward wrote:

Guy Macon wrote:

What we have here is, in my opinion, a liar. I don't believe that
he has ever designed any audio equipment.

Your kidding right?

Graham has designed more pro audio gear that has been used by world
famous musicians then you have had hot dinners, mate.

Thank you for that clarification Kevin !

I have *never ever* in my entire working life found myself the recipient of
a trail of abuse so witless and uninformed as that created by Guy Macon and
his cronies !

It is *astonishingly disturbing*. It's like the ppl who think if that they
simply repeat their lies often enough - other ppl will believe them ! I'm
truly staggered.

I presume that was meant tongue-in-cheek after the trail of lies and
half-truths you have scattered throughout this thread and the "3 dB
bandwidth" one.

Nobody has created a "trail of abuse" except you. Hardly anyone has
replied with abusive language towards you, despite your having piled
abuse on nearly everyone. We have given you every opportunity to
support your assertions with relevant facts and you have failed to do
so.

You have been well and truly caught out telling lies - can you blame
someone if they have doubts about some of your other claims?


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[Kevin Aylward]

Adrian Tuddenham wrote:

Kevin Aylward <see_website@anasoft.co.uk> wrote:



The standard we were discussing (which forms the title of this
thread) was the decibel.

The AES did not develop the decibel standard, Bell Labs did.

And your point would be?

That "Pooh Bear" has repeatedly and knowingly lied to this group.

ROTFLMAO

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Kevin Aylward]

Pooh Bear wrote:

Kevin Aylward wrote:

Guy Macon wrote:

What we have here is, in my opinion, a liar. I don't believe that
he has ever designed any audio equipment.

Your kidding right?

Graham has designed more pro audio gear that has been used by world
famous musicians then you have had hot dinners, mate.

Thank you for that clarification Kevin !

I have *never ever* in my entire working life found myself the
recipient of a trail of abuse so witless and uninformed as that
created by Guy Macon and his cronies !

I had similar nonsense from Mr. Macon. He is a non starter.

It is *astonishingly disturbing*. It's like the ppl who think if that
they simply repeat their lies often enough - other ppl will believe
them ! I'm truly staggered.

Indeed.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Don Bowey]

On 6/30/05 12:45 PM, in article
NZXwe.40671$Vo6.38475@fe3.news.blueyonder.co.uk, "Kevin Aylward"
<see_website@anasoft.co.uk> wrote:

Pooh Bear wrote:
Kevin Aylward wrote:

Guy Macon wrote:

What we have here is, in my opinion, a liar. I don't believe that
he has ever designed any audio equipment.

Your kidding right?

Graham has designed more pro audio gear that has been used by world
famous musicians then you have had hot dinners, mate.

Thank you for that clarification Kevin !

I have *never ever* in my entire working life found myself the
recipient of a trail of abuse so witless and uninformed as that
created by Guy Macon and his cronies !

I had similar nonsense from Mr. Macon. He is a non starter.


It is *astonishingly disturbing*. It's like the ppl who think if that
they simply repeat their lies often enough - other ppl will believe
them ! I'm truly staggered.

Indeed.

Indeed what?

Poo alludes to the idea that everyone who has anything negative to say about
him, is a liar, while he lies and demeans with a broad brush.

Don

 

[Pooh Bear]

Bob wrote:

You may want to re-think that.

Here are some specs for non-loaded 26G pic cable; a common Exchange Cable
type:

Resistance per mile from 1 Hz to 15kHz = 441 Ohms. Beyond that freq the
skin effect starts increasing the resistance. At 1MHz it's 463 Ohms, and
at
5 MHz it's 2044 Ohms.


Approximate Z per mile at 1 Hz is 20,562 Ohms, and is up to 2057 Ohms at
100
Hz.

In the band from 300 Hz to 3 kHz the Z runs from 1189 Ohms to 383 Ohms.
At
5Mhz the Z is 96 Ohms/mile.

In rural areas that are still served by copper, rather than a nearby mux,
the cables are H88 loaded, and can be assumed to have a 600 Ohm Z.

Don

An ex-Toll bastard.


These load coils were a great invention (for their time). Whoever invented
them (I think it was Heaviside) was pretty short-sighted, though. He should
have known it would really fugg-up our DSL service!

Graham, you've really caused quite a stir, with this thread. I'll bet you
didn't expect a sort of Spanish Inquisition, did you?

I may have underestimated the level of ignorance displayed by a cabal of about
3 posters for sure !

Actually, the whole thing 'kicked off' in another thread about 3dB bandwidth
where Mr Ghee Maroon casually stated that 'matched impedance working' caused a
3 dB signal drop. I assumed it was a simple oversight style mistake on his part
and mentioned he should have said 6dB and well..........

The rest follows from there. It seemed to be worth a new thread though.

I am staggerred that a few ppl who presumably pass themselves off as
professional engineers clearly haven't the first clue about the correct usage
of the decibel.

Cheers, Graham

 

[Guy Macon]

Keeping in mind that because of my killfile I cannot see any posts
by Pooh Bear or Kevin Aylward, both of whom think that personal
attacks are an acceptable substitute for a civil discussion of
the issue at hand...

Adrian Tuddenham wrote:

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:

Kevin Aylward wrote:

Guy Macon wrote:

What we have here is, in my opinion, a liar. I don't believe that
he has ever designed any audio equipment.

Your kidding right?

Graham has designed more pro audio gear that has been used by world
famous musicians then you have had hot dinners, mate.

Name one. My accomplishments are on record for all to see.

Thank you for that clarification Kevin !

I have *never ever* in my entire working life found myself the recipient of
a trail of abuse so witless and uninformed as that created by Guy Macon and
his cronies !

Ooh! I have *cronies*?? Whooduthunkit?

It is *astonishingly disturbing*. It's like the ppl who think if that they
simply repeat their lies often enough - other ppl will believe them ! I'm
truly staggered.

I presume that was meant tongue-in-cheek after the trail of lies and
half-truths you have scattered throughout this thread and the "3 dB
bandwidth" one.

Nobody has created a "trail of abuse" except you. Hardly anyone has
replied with abusive language towards you, despite your having piled
abuse on nearly everyone. We have given you every opportunity to
support your assertions with relevant facts and you have failed to do
so.

You have been well and truly caught out telling lies - can you blame
someone if they have doubts about some of your other claims?

Having Kevin Aylward stick up for him is the final proof. Now I *know*
that he has never designed anything that went into production. At
least Aylward has created something; the worst user interface on earth.
(see below)

Neither one of them has stood there watching 100,000 copies per day
of a design they created go out the door, knowing that if they start
failing final test it will cost a million dollars a day.




The Kevin Aylward memorial "Worst Human
Interface on Earth" Award goes to:

+-?----+
| |
|( )? |
| |
|( )? |
| |
|( )? |
| |
|( )? |
| |
|( )? |
| |
|( )? |
|......|
|(.)?..|
|......|
|(.)?..|
|......|
|......|
|......|
|......|
+------+

http://www.anasoft.co.uk/ee.gif
http://www.anasoft.co.uk/screenshot.html

Features: on the last menu a section labled "?" gives
you the choice between "?", "?", "?", "?", "?", "?", "?",
"?", -with the last two greyed out - then repeats the same
menu full off question marks again! Brilliant!!

 

[Pooh Bear]

Guy Macon wrote:

Keeping in mind that because of my killfile I cannot see any posts
by Pooh Bear or Kevin Aylward, both of whom think that personal
attacks are an acceptable substitute for a civil discussion of
the issue at hand...

Top-posting cnut ! ;-)

Graham

 

[Kevin Aylward]

Don Bowey wrote:

On 6/30/05 12:45 PM, in article
NZXwe.40671$Vo6.38475@fe3.news.blueyonder.co.uk, "Kevin Aylward"
see_website@anasoft.co.uk> wrote:

Pooh Bear wrote:
Kevin Aylward wrote:

Guy Macon wrote:

What we have here is, in my opinion, a liar. I don't believe that
he has ever designed any audio equipment.

Your kidding right?

Graham has designed more pro audio gear that has been used by world
famous musicians then you have had hot dinners, mate.

Thank you for that clarification Kevin !

I have *never ever* in my entire working life found myself the
recipient of a trail of abuse so witless and uninformed as that
created by Guy Macon and his cronies !

I had similar nonsense from Mr. Macon. He is a non starter.


It is *astonishingly disturbing*. It's like the ppl who think if
that they simply repeat their lies often enough - other ppl will
believe them ! I'm truly staggered.

Indeed.

Indeed what?

Poo alludes to the idea that everyone who has anything negative to
say about him, is a liar, while he lies and demeans with a broad
brush.

You are entitled to your views, as misguided as they are.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Kevin Aylward]

Guy Macon wrote:

Keeping in mind that because of my killfile I cannot see any posts
by Pooh Bear or Kevin Aylward, both of whom think that personal
attacks are an acceptable substitute for a civil discussion of
the issue at hand...

You wish. Get real, I never make personal derogatory remarks in NG
postings. Regarding, your self, I have noticed many such comments.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Don Bowey]

On 6/30/05 10:35 PM, in article
BC4xe.44214$Vo6.34846@fe3.news.blueyonder.co.uk, "Kevin Aylward"
<see_website@anasoft.co.uk> belched:

Don Bowey wrote:
On 6/30/05 12:45 PM, in article
NZXwe.40671$Vo6.38475@fe3.news.blueyonder.co.uk, "Kevin Aylward"
see_website@anasoft.co.uk> wrote:

Pooh Bear wrote:
Kevin Aylward wrote:

Guy Macon wrote:

What we have here is, in my opinion, a liar. I don't believe that
he has ever designed any audio equipment.

Your kidding right?

Graham has designed more pro audio gear that has been used by world
famous musicians then you have had hot dinners, mate.

Thank you for that clarification Kevin !

I have *never ever* in my entire working life found myself the
recipient of a trail of abuse so witless and uninformed as that
created by Guy Macon and his cronies !

I had similar nonsense from Mr. Macon. He is a non starter.


It is *astonishingly disturbing*. It's like the ppl who think if
that they simply repeat their lies often enough - other ppl will
believe them ! I'm truly staggered.

Indeed.

Indeed what?

Poo alludes to the idea that everyone who has anything negative to
say about him, is a liar, while he lies and demeans with a broad
brush.

You are entitled to your views, as misguided as they are.

ESAD

 

[Don Bowey]

On 6/28/05 10:26 AM, in article wLfwe.38930$rb6.4094@lakeread07, "John
Perry" <jp@no.spam> wrote, in part:

snip

In fact, twisted pair is around 100 ohms from DC to microwave

You may want to re-think that.

Here are some specs for non-loaded 26G pic cable; a common Exchange Cable
type:

Resistance per mile from 1 Hz to 15kHz = 441 Ohms. Beyond that freq the
skin effect starts increasing the resistance. At 1MHz it's 463 Ohms, and at
5 MHz it's 2044 Ohms.


Approximate Z per mile at 1 Hz is 20,562 Ohms, and is up to 2057 Ohms at 100
Hz.

In the band from 300 Hz to 3 kHz the Z runs from 1189 Ohms to 383 Ohms. At
5Mhz the Z is 96 Ohms/mile.

In rural areas that are still served by copper, rather than a nearby mux,
the cables are H88 loaded, and can be assumed to have a 600 Ohm Z.

Don

An ex-Toll bastard.

 

[Mac]

On Tue, 28 Jun 2005 19:00:11 -0700, Don Bowey wrote:

On 6/28/05 10:26 AM, in article wLfwe.38930$rb6.4094@lakeread07, "John
Perry" <jp@no.spam> wrote, in part:

snip

In fact, twisted pair is around 100 ohms from DC to microwave


You may want to re-think that.

Here are some specs for non-loaded 26G pic cable; a common Exchange Cable
type:

Resistance per mile from 1 Hz to 15kHz = 441 Ohms. Beyond that freq the
skin effect starts increasing the resistance. At 1MHz it's 463 Ohms, and at
5 MHz it's 2044 Ohms.


Approximate Z per mile at 1 Hz is 20,562 Ohms, and is up to 2057 Ohms at 100
Hz.

In the band from 300 Hz to 3 kHz the Z runs from 1189 Ohms to 383 Ohms. At
5Mhz the Z is 96 Ohms/mile.

In rural areas that are still served by copper, rather than a nearby mux,
the cables are H88 loaded, and can be assumed to have a 600 Ohm Z.

Don

An ex-Toll bastard.

I think Don was talking about the characteristic impedance. IIRC, Don is
probably wrong about the characteristic impedance at low frequencies.
There was a thread here about that some time ago, where Reg Edwards, I
think, set a lot of people straight. But at modest frequencies up to VHF,
a twisted pair is right around 100 Ohms, regardless of length.

At higher frequencies twisted pairs are largely unusable due to
attenuation, but that doesn't mean that the characteristic impedance is
not around 100 Ohms. For all I know, it is.

--Mac

 

[John Larkin]

On Sat, 02 Jul 2005 01:16:25 GMT, Mac <foo@bar.net> wrote:

On Tue, 28 Jun 2005 19:00:11 -0700, Don Bowey wrote:

On 6/28/05 10:26 AM, in article wLfwe.38930$rb6.4094@lakeread07, "John
Perry" <jp@no.spam> wrote, in part:

snip

In fact, twisted pair is around 100 ohms from DC to microwave


You may want to re-think that.

Here are some specs for non-loaded 26G pic cable; a common Exchange Cable
type:

Resistance per mile from 1 Hz to 15kHz = 441 Ohms. Beyond that freq the
skin effect starts increasing the resistance. At 1MHz it's 463 Ohms, and at
5 MHz it's 2044 Ohms.


Approximate Z per mile at 1 Hz is 20,562 Ohms, and is up to 2057 Ohms at 100
Hz.

In the band from 300 Hz to 3 kHz the Z runs from 1189 Ohms to 383 Ohms. At
5Mhz the Z is 96 Ohms/mile.

In rural areas that are still served by copper, rather than a nearby mux,
the cables are H88 loaded, and can be assumed to have a 600 Ohm Z.

Don

An ex-Toll bastard.

I think Don was talking about the characteristic impedance. IIRC, Don is
probably wrong about the characteristic impedance at low frequencies.
There was a thread here about that some time ago, where Reg Edwards, I
think, set a lot of people straight. But at modest frequencies up to VHF,
a twisted pair is right around 100 Ohms, regardless of length.

At higher frequencies twisted pairs are largely unusable due to
attenuation, but that doesn't mean that the characteristic impedance is
not around 100 Ohms. For all I know, it is.

--Mac

At low frequencies, for tp or coax, the resistive loss starts to make
the impedance go up. At very high frequencies, non-TEM propagation
modes make the impedance a complex function of frequency. At very high
frequencies, coax is squeezed between these effects: you have to make
it small to supress modes, but that makes the ohmic loss go up.
Somewhere in the 50-100 GHz range, coax becomes sort of useless.

John

 

[Kevin Aylward]

John Perry wrote:

Pooh Bear (and others) wrote:

600 ohms working was only ever needed for long 'land lines' - and
how many of
them still exist ? It's all concentrated at the local exchange and
distributed digitally via optic fibre these days !


Actually, in some sparsely populated rural US areas there are still
the ancient 600-ohm lines in use. You can recognize them by the bare
wires held up on glass insulators and twisted every few hundred feet
by dropping one to a lower crosstie so it can swap places on the next
crosstie with its return wire. They're now used mainly for frequency-
division multiplexing (FDM), I think, but there are still a few out
there.

I *know* ! It's actually difficult to make a practical twisted pair
that *isn't* around 100 ohms at HF !


In fact, twisted pair is around 100 ohms from DC to microwave,

Ahmmm...


Zo = sqrt((R+jwL)/(G+jwC))

at w=0, i.e. DC, its:

Zo=sqrt(R/G)

DC conductance, i.e. leakage resistance, is essential 0. So, at DC , the
impedance is, essentially, infinite.

Why anyone should think a bit of cable at DC has a 100 ohm impedance is
quite beyond me. Batteries wouldnt last very long if cables were so
bloody dreadful.


Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Robert]

"Kevin Aylward" <see_website@anasoft.co.uk> wrote in message
news:Zzuxe.59226$Vo6.31925@fe3.news.blueyonder.co.uk...

John Perry wrote:
Pooh Bear (and others) wrote:

600 ohms working was only ever needed for long 'land lines' - and
how many of
them still exist ? It's all concentrated at the local exchange and
distributed digitally via optic fibre these days !


Actually, in some sparsely populated rural US areas there are still
the ancient 600-ohm lines in use. You can recognize them by the bare
wires held up on glass insulators and twisted every few hundred feet
by dropping one to a lower crosstie so it can swap places on the next
crosstie with its return wire. They're now used mainly for frequency-
division multiplexing (FDM), I think, but there are still a few out
there.

I *know* ! It's actually difficult to make a practical twisted pair
that *isn't* around 100 ohms at HF !


In fact, twisted pair is around 100 ohms from DC to microwave,

Ahmmm...


Zo = sqrt((R+jwL)/(G+jwC))

at w=0, i.e. DC, its:

Zo=sqrt(R/G)

DC conductance, i.e. leakage resistance, is essential 0. So, at DC , the
impedance is, essentially, infinite.

Why anyone should think a bit of cable at DC has a 100 ohm impedance is
quite beyond me. Batteries wouldnt last very long if cables were so bloody
dreadful.


Kevin Aylward

Two straight pieces of wire have infinite Impedance at DC? If you hook them
to a car battery and shorted the other ends, no current would flow?

I suspect reality would contradict your formula and the wires (normal, not
huge) would melt.

Robert

 

[Pooh Bear]

Kevin Aylward wrote:

John Perry wrote:
Pooh Bear (and others) wrote:

600 ohms working was only ever needed for long 'land lines' - and
how many of
them still exist ? It's all concentrated at the local exchange and
distributed digitally via optic fibre these days !


Actually, in some sparsely populated rural US areas there are still
the ancient 600-ohm lines in use. You can recognize them by the bare
wires held up on glass insulators and twisted every few hundred feet
by dropping one to a lower crosstie so it can swap places on the next
crosstie with its return wire. They're now used mainly for frequency-
division multiplexing (FDM), I think, but there are still a few out
there.

I *know* ! It's actually difficult to make a practical twisted pair
that *isn't* around 100 ohms at HF !


In fact, twisted pair is around 100 ohms from DC to microwave,

Ahmmm...

Zo = sqrt((R+jwL)/(G+jwC))

at w=0, i.e. DC, its:

Zo=sqrt(R/G)

DC conductance, i.e. leakage resistance, is essential 0. So, at DC , the
impedance is, essentially, infinite.

Why anyone should think a bit of cable at DC has a 100 ohm impedance is
quite beyond me. Batteries wouldnt last very long if cables were so
bloody dreadful.

Check the AES-3 spec about digital audio links. The original idea was to use
standard mic cables for digital AES/EBU ( now usually referred to as AES-3
) connections.

It worked out that standard mic cable has a 110 ohms characteristic
impedance in the MHz region.

It also turned out that 'standard mic cable' wasn't ideal, so specilaist
types are now available to meet the spec, notably from Belden for example.

Graham

 

[Guy Macon]

Robert wrote:

Kevin Aylward wrote...

John Perry wrote:

In fact, twisted pair is around 100 ohms from DC to microwave,

Ahmmm...

Zo = sqrt((R+jwL)/(G+jwC))

at w=0, i.e. DC, its:

Zo=sqrt(R/G)

DC conductance, i.e. leakage resistance, is essential 0. So, at DC , the
impedance is, essentially, infinite.

Why anyone should think a bit of cable at DC has a 100 ohm impedance is
quite beyond me. Batteries wouldnt last very long if cables were so bloody
dreadful.

Kevin Aylward

Two straight pieces of wire have infinite Impedance at DC? If you hook them
to a car battery and shorted the other ends, no current would flow?

I suspect reality would contradict your formula and the wires (normal, not
huge) would melt.

Aylward makes a common error among those who have failed to grasp
the true nature of the physical system they are discussing.

When a transmission line is connected to a DC voltage, it really does
behave like a resistor equal in value to the transmission line's
characteristic impedance, but only for as long as it takes the pulse
to reach the end of the transmission line and return; at that point
in time what is on the end has an effect.. Before that point in time
the laws of physics do not allow whatever is on the end to have any
effect at all on the source.

Let's assume that the transmission line is a mile long and is open
at the far end. That's roughly 16 microseconds round trip, IIRC.
For those 16us, the source sees only the transmission line's
characteristic impedance. Then the infinite impedance at the end
starts to have an effect.

If the cable is infinitely long, the source sees the transmission
line's characteristic impedance forever. Not having an infinitely
long cable at hand, we can get the exact same effect by terminating
the end of the cable with a load that matches the line's characteristic
impedance.

Those of us who have been doing this for many years will remember
that the older term for characteristic impedance was surge impedance.
If we had kept that term, people like Kevin wouldn't be so confused.

(All of the above assumes a perfect transmission line. In the real
world there are at least two effects that make the characteristic
impedance vary with frequency (they don't however, cause Kevin's
"at DC, the impedance is, essentially, infinite" false statement
to become true.) These are skin effect and frequency dependence
o the dielectric constant. They don't matter near DC, but I mention
them for completeness.)

 

[keith]

On Sat, 02 Jul 2005 14:36:30 +0000, Guy Macon wrote:

Robert wrote:

Kevin Aylward wrote...

John Perry wrote:

In fact, twisted pair is around 100 ohms from DC to microwave,

Ahmmm...

Zo = sqrt((R+jwL)/(G+jwC))

at w=0, i.e. DC, its:

Zo=sqrt(R/G)

DC conductance, i.e. leakage resistance, is essential 0. So, at DC , the
impedance is, essentially, infinite.

Why anyone should think a bit of cable at DC has a 100 ohm impedance is
quite beyond me. Batteries wouldnt last very long if cables were so bloody
dreadful.

Kevin Aylward

Two straight pieces of wire have infinite Impedance at DC? If you hook them
to a car battery and shorted the other ends, no current would flow?

I suspect reality would contradict your formula and the wires (normal, not
huge) would melt.

Aylward makes a common error among those who have failed to grasp
the true nature of the physical system they are discussing.

Aylward may be a lot of things, but ignorant of the relevant physics isn't
one of them.

When a transmission line is connected to a DC voltage, it really does
behave like a resistor equal in value to the transmission line's
characteristic impedance, but only for as long as it takes the pulse to
reach the end of the transmission line and return; at that point in time
what is on the end has an effect.. Before that point in time the laws
of physics do not allow whatever is on the end to have any effect at all
on the source.

And there is no AC component in this?

Let's assume that the transmission line is a mile long and is open at
the far end. That's roughly 16 microseconds round trip, IIRC. For those
16us, the source sees only the transmission line's characteristic
impedance. Then the infinite impedance at the end starts to have an
effect.

If the cable is infinitely long, the source sees the transmission line's
characteristic impedance forever. Not having an infinitely long cable
at hand, we can get the exact same effect by terminating the end of the
cable with a load that matches the line's characteristic impedance.

As has been pointed out here, only if the transmission line is ideal (R=0,
G=infinite). Real transission lines aren't.

Those of us who have been doing this for many years will remember that
the older term for characteristic impedance was surge impedance. If we
had kept that term, people like Kevin wouldn't be so confused.

Pompous ass.

(All of the above assumes a perfect transmission line. In the real
world there are at least two effects that make the characteristic
impedance vary with frequency (they don't however, cause Kevin's "at DC,
the impedance is, essentially, infinite" false statement to become
true.) These are skin effect and frequency dependence o the dielectric
constant. They don't matter near DC, but I mention them for
completeness.)

Wrong. At DC only G matters.

....or are we going to get in the AC/DC argument all over again? ;-)

--
Keith

 

[RST Engineering (jw)]

It has nothing at all to do with your analysis (which I find rather complete
and correct) but a "radar mile" (out and back) is 10.7 microseconds. Just
to pick the flyspecs out of the pepper {;-)


Jim

Let's assume that the transmission line is a mile long and is open
at the far end. That's roughly 16 microseconds round trip, IIRC.
For those 16us, the source sees only the transmission line's
characteristic impedance. Then the infinite impedance at the end
starts to have an effect.

 

[John Larkin]

On Sat, 02 Jul 2005 11:12:56 -0400, keith <krw@att.bizzzz> wrote:

On Sat, 02 Jul 2005 14:36:30 +0000, Guy Macon wrote:

Those of us who have been doing this for many years will remember that
the older term for characteristic impedance was surge impedance. If we
had kept that term, people like Kevin wouldn't be so confused.

Pompous ass.

I disagree. I think "fathead" is the more precise term here.

John