krw wrote:
In article ,
says...
Foxtrot wrote:
... snip ...
Is there is a greaterlikelihood of hum if I connect a "2 wire"
phone extension by using one wire from a twisted pair and taking
the second wire from a different twisted pair?
Yes. The idea of twisted pairs is that an interference appears on
both lines, and thus tends to cancel itself. Separating the lines
makes it easy for unequal induction.
Twisting also makes the loop area low (average over a long stretch
is nil). Separating them makes a large loop, increasing the size of
the antenna.
That is not a valid analysis. It is a transmission
line, not an antenna.
Consider that the effect, both for relatively small
gauge cables, such as the ubiquitous 26 gauge used
today, is *exactly* the same as the effect on the open
wire lines used in the 30's and 40's with several inches
of separate between a pair of much larger copperclad
steel wires. And while the twist on some cable is
measured per inch, on typical telephone cable it is
measured in many inches per twist, and on those old open
wire lines it was in hundreds of yards per twist.
--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)