From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Why terminate ?
Date: Sat, 19 Oct 2002 23:50:56 GMT
NNTP-Posting-Date: Sat, 19 Oct 2002 16:50:56 PDT
Steve Drake wrote:
> Hello all. I looking for all the good reasons to terminate a
> connector properly. For example when the signal generator
> says its a 50 ohm output you should put a 50 ohm terminator
> on the end of the cable because:
> To get maximum power transfer from the output to the input.
> To reduce the VSWR on the line (but this only maters in high frequency
> circuits, then what is high frequency?, has to do with line lenght)
> It helps the output circuitry to operate more linerly, kind of like
> the MPT above.
> I heard this week that it can help reduce noise on the line, but don't
> know how.
> Again to properly match the line to the terminatation again to reduce
> Are there any other reasons to use a terminator? What if you are
> measureing a signal on a scope at low frequencies (ie 1-10 kHz)
> do you have to terminate the line, why not just measure the signal
> from the generator.
> Thanks for any more insite you can give me into the reasons for
> proper termination of a line, but does it really matter at what freq.
> you are working at?
At low frequencies, it doesn't much matter. At high frequencies, it is
important. Your cable will have a delay of about a nanosecond per foot.
If that is at all a significant fraction of wavelength, you need to
terminate. Someone also mentioned that, if nothing else, the terminator
will make settings of signal attenuators correct. Line noise from lack
of termination is largely two problems. The higher impedance without a
terminator makes external noise couple more. In addition, an
unterminated cable will have reflections which sometimes look like
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com