Hum from phone wires running next to mains?

Ivor Jones wrote:
"CBFalconer" wrote:

[snip]

I replaced your non-standard (: quote markers with
the normal ''. Please don't use thos non-standard
characters. They foul up other software.

With respect, and without wishing to start a row, that's *your*
problem. I use non-standard quote marks for a purpose. If your
system can't cope with that, then it's up to *you* to do
something about it. I have been using the quote marks I use for
several years and you are the first to complain.

Well, I said my piece. The normal method of handling it is the
casual plonk.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: http://cbfalconer.home.att.net
Try the download section.



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

In article , says...
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.

It sure as hell is. Open up the loop and it makes a *wonderful*
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.

....and open-wire transmission lines won't pick up stray noise?

--
Keith

"Floyd L. Davidson" wrote:
CBFalconer wrote:

In North America again (I don't know about elsewhere) the normal
phone uses 3 wires to connect to the two wires of the phone
circuit. The yellow wire carries the ring signal. Just
disconnect that and the phone won't ring, and the load is zero.

I don't recall any system in North America that put ring
voltage on a separate wire. The yellow wire is
generally not connected unless one 4-wire cable is used
for two separate telephone lines.

In North America the "normal" line uses only 2 wires.
The audio signal is applied between the "tip" and the
"ring" of a single pair. "Ring Current" and "Loop
Current" are also applied between the Tip and the Ring
of the same pair.

Commonly used drop cable has four wires: Green is the
Tip and Red is the Ring (positive and negative,
repectively for the DC loop current), while the Yellow
and the Black wires are not used. (Note that the DC
voltages used by telephone companies are negative with
respect to ground, hence for DC the Tip wire is at
ground potential, and the Ring wire has a negative
potential. But the Tip is not at ground potential for
Ring Current or for the audio signal.)

One configuration often seen includes a second line on
the same cable, using Yellow and Black as Tip and Ring.

Historically the Yellow wire was, for a few years, used
for a small AC voltage (nominally 6.8 volts) to power a
lamp circuit on some telephone set models.

Another historical use had the Yellow wire as a ground
for party line service from the old style mechanical
switching systems (such as the Step or Stroeger
switching systems once used by the Bell System and by
Automatic Electric). On those systems the ring current
was applied between either Tip or Ring and ground, which
was supplied to the telephone set on the Yellow wire.

Well, it is possible that my memory is fouled. Haven't needed to
disconnect ringers for at least 20 years.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: http://cbfalconer.home.att.net
Try the download section.



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

krw wrote:
In article , says...
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.

It sure as hell is. Open up the loop and it makes a *wonderful*
antenna.

It's a "wonderful" antenna regardless. But it's a
single conductor long wire antenna. Changing the
spacing is merely changing the effective diameter of the
single conductor. To get any other effect requires
spacing that is significant in terms of wavelength
(greater than perhaps 1/8th of a wavelength, for
example).

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.

...and open-wire transmission lines won't pick up stray noise?

It picks up as much, or as little, as unshielded twisted
pair of smaller gauge and closer spacing. That's the
point... there isn't any difference. In either case
what you have is a single conductor longwire antenna, not
a loop antenna, until the spacing is a significant fraction
of a wavelength.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Ivor Jones wrote:


With no respect,


Plonk


--
My sig file can beat up your sig file!

In alt.engineering.electrical Michael A. Terrell wrote:
| Ivor Jones wrote:
|
|
| With no respect,
|
|
| Plonk

You should do that more often.

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / |
|------------------------------------/-------------------------------------|

Ivor Jones wrote:

"CBFalconer" wrote in message

: : Ivor Jones wrote:

[snip]

: : I replaced your non-standard (: quote markers with
: : the normal ''. Please don't use thos non-standard
: : characters. They foul up other software.

With respect, and without wishing to start a row, that's *your* problem.
I use non-standard quote marks for a purpose. If your system can't cope
with that, then it's up to *you* to do something about it. I have been
using the quote marks I use for several years and you are the first to
complain.

Ivor


Non-standard usage can make your posts harder to understand,
and more difficult for others. Apparently, you don't care.
I'm just adding one more response to let you know that your
non-standard usage is not appreciated.

Ed

"Floyd L. Davidson" wrote in message

: : "Ivor Jones" wrote:
: : : "CBFalconer" wrote in message
: : :
: : : : : Ivor Jones wrote:
: : :
: : : [snip]
: : :
: : : : : I replaced your non-standard (: quote markers
: : : : : with the normal ''. Please don't use thos
: : : : : non-standard characters. They foul up other
: : : : : software.
: : :
: : : With respect, and without wishing to start a row,
: : : that's *your* problem. I use non-standard quote marks
: : : for a purpose. If your system can't cope with that,
: : : then it's up to *you* to do something about it. I
: : : have been using the quote marks I use for several
: : : years and you are the first to complain.
: :
: : Consider for a bit just how absurd that statement is...

Which part..? The part where I say I use non-standard quotes for a reason,
or the part where I said nobdy has so far complained..?

: : Are you posting your articles for your personal
: : edification, or are they intended to be read by an
: : audience? Who should you format them for, yourself or
: : the audience?

Both.

: : Your non-standard quote characters are *not* appreciated
: : by the audience, and indeed the more sophisticated
: : members that you might want to appeal to the most are
: : the ones most likely to make use of software options
: : based on the quote marks.

So why, in my 10+ years of Usenet use, is this the first complaint..?

: : What your formatting style does, is tell the reader what
: : your priorities are, and that your ability to comprehend
: : the effect is apparently impaired.

Your ability to comprehend my reply appears to be impaired also.

plonk

Ivor

"ehsjr" wrote in message
news:3HTzj.19815$ES.6877@trnddc05

[snip]

: : Non-standard usage can make your posts harder to
: : understand, and more difficult for others. Apparently,
: : you don't care. I'm just adding one more response to
: : let you know that your non-standard usage is not
: : appreciated.

Ok, you're the *second* complaint in 10+ years. When that figure gets to a
noticable percentage, I might sit up and take notice.

Ivor

: :
: : Ed

wrote:

In alt.engineering.electrical Michael A. Terrell wrote:
| Ivor Jones wrote:
|
|
| With no respect,
|
|
| Plonk

You should do that more often.


I plonk for arrogance, not ignorance. You have NOTHING to worry
about.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida