> krw
att.bizzzzzzzzzz> wrote:>>> krw
att.bizzzzzzzzzz> wrote:>>>>> krw
att.bizzzzzzzzzz> wrote:>>>>>>> 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).
>>
>>Absolute nonsense.
>
> Actually, that's why it works so well as a balanced
> transmission line.
Sure, it's a transmission line for the t-wave on the line. It's
also an antenna, with the gain proportional to the area of the loop.
Try running that open line next to a power line.
>>>>> 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.
>>
>>Bullsnit. Try reading your EE100 text again.
>
> I'd suggest studying transmission lines and antennas.
> Start with Kraus.
Get real Floyd!
--
Keith
