Hi


Why characteristic impedance of transmission line isn't important at
low frequencies (1000kHz) and it is one of the main parameters in RF?
At high frequencies if  a generator isn't matched  with the impedance
of the line the reflection of the power can damage the genarator, why
isn't that the case at low frequencies? Or am I wrong about the
destroying the generator?
(example: If we connect high power audio amp to speaker we don't have
to worry about the  characteristic impedance of the cable)  Can
somebody explain this?


Thanks

<s...@net.hr> wrote in message 
news:1...@w5g2000hsg.googlegroups.com...
> Hi
>
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000kHz) and it is one of the main parameters in RF?
> At high frequencies if  a generator isn't matched  with the impedance
> of the line the reflection of the power can damage the genarator, why
> isn't that the case at low frequencies? Or am I wrong about the
> destroying the generator?
> (example: If we connect high power audio amp to speaker we don't have
> to worry about the  characteristic impedance of the cable)  Can
> somebody explain this?
>
>

Transmission line effects are negligible if the line length is a tiny 
fraction of a wavelength.

s...@net.hr wrote:
> Hi
> 
> 
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000kHz) and it is one of the main parameters in RF?
> At high frequencies if  a generator isn't matched  with the impedance
> of the line the reflection of the power can damage the genarator, why
> isn't that the case at low frequencies? Or am I wrong about the
> destroying the generator?
> (example: If we connect high power audio amp to speaker we don't have
> to worry about the  characteristic impedance of the cable)  Can
> somebody explain this?
> 
> 
> Thanks
> 
Totally wrong.
Just ask a 'serious' electic company engineer on matching generators to 
loads with and without reflections.
It is the physics that is involved, not beliefs or frequencies.

HTH

Stanislaw

s...@net.hr wrote:

> Hi
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000kHz)

Who says it isn't ? That's the upper end of the DSL frequencies on a phone line
and it's very important to use transmissin line thinking for that to work.

Graham

s...@net.hr wrote:

> (example: If we connect high power audio amp to speaker we don't have
> to worry about the  characteristic impedance of the cable)  Can
> somebody explain this?

Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.  A speaker cable is
maybe 10m. There's no transmission line effect to consider here.

In long-distance telephony, the long length of the cables make transmission line
thinking important even at these audio frequncies.


Graham

Eeyore je napisao/la:
> s...@net.hr wrote:
>
> > Hi
> >
> > Why characteristic impedance of transmission line isn't important at
> > low frequencies (1000kHz)
>
> Who says it isn't ? That's the upper end of the DSL frequencies on a phone line
> and it's very important to use transmissin line thinking for that to work.
>
> Graham

Sorry, I meant to say 1000Hz not 1000kHz

"Andrew Holme"
>
> Transmission line effects are negligible if the line length is a tiny 
> fraction of a wavelength.
>

**  WRONG !!

Same old ham radio bollocks trotted out as fact about a different area of 
electronics.




.......  Phil 

"Eeysore Fucking Pommy IDIOT "

>
> Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.


**  NOT  AGAIN   !!!

Can't the Graham Stevenson MORON ever get a

FUCKING decimal point right  ?????

Or any other point right ??



.......  Phil

<s...@net.hr>
>
> Why characteristic impedance of transmission line isn't important at
> low frequencies (1000Hz) and it is one of the main parameters in RF?


** That is not a correct statement -  just another myth from the mouths and 
keyboards of fools. All signal and power cables have a characteristic 
impedance and it can matter at low frequencies.

The most important fact about characteristic impedance is that IF the load 
on the end matches the cable's characteristic impedance -  the parallel 
capacitance & series inductance of the cable no longer has any effect.

Capacitance in a mic cable 100 metres long can have a significant effect on 
the high frequency output of a mic.

The inductance of a twin wire speaker cable of only 10 metres long will 
cause a drop in level at 20kHz of several dB if the load impedance is 1 ohm.



......  Phil

Phil Allison wrote:

> "Eeysore Fucking Pommy IDIOT "
> >
> > Audio only goes to 20kHz. The wavelength @ 20kHz is 1.5 km.
>
> **  NOT  AGAIN   !!!
>
> Can't the Graham Stevenson MORON ever get a
>
> FUCKING decimal point right  ?????
>
> Or any other point right ??

It's that damn Windows calculator !

Graham