Hum from phone wires running next to mains?

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Keep up the baloney Floyd. You're good at it.

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If it were baloney you should be able to demonstrate it fairly easily; instead you post insults and can't follow up to even the lowest level of technical discussion.
Do you understand the comparison between the effects of multiple wires used in rhombic design to the multiple wires used for folded dipole design? (And do you understand the one difference?)
And do you have any idea how silly it is to say that folded dipoles don't work if they are twisted???? Of course many, if not most, homemade folded dipoles used at HF frequencies do in fact end up being twisted...
Go to a library, read Kraus.

Foxtrot wrote:
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That practice is known in the North American communications industry as a split pair. It is usually the cause of a host of troubles of which induced noise is only the most common.

On Tue, 04 Mar 2008 21:22:30 +0000, phil-news-nospam wrote:
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Very interesting.
Please can you advise on how these twisted pairs compare with
1. shielded audio cable and 2. rf coax.
In case 1 both the wanted signal and the noise are in the audio frequency range.
In case 2 the electricity supply noise contains harmonics of similar frequency to the wanted rf signal.

| On Tue, 04 Mar 2008 21:22:30 +0000, phil-news-nospam wrote: |
|> |> |>It is quite difficult to induce hum into telephone wiring. Use twisted |> |>pair cabling rather than the flat ready-made extension cables. |> | |> | Exactly! |> | The phone company has millions of miles of cable running right below |> | power lines and hundreds literally touching each other in the jacket of |> | the cable. That little twist they put in the pairs is excellent in |> | isolating them from crosstalk. |> |> That twist is a great little means to ensure induced signals, whatever |> they may be, are induced in equal amount on both wires, so they do not |> contribute to the actual intended signal that is a differential between |> those two wires. |> |> However, a risk exists when two different pairs are present next to each |> other and each pair is twisted at the same pitch. The signal carried by |> one can end up being induced differentially on the other. So don't twist |> those power lines, or if you do, twist them at a pitch with a ratio to the |> phone line twist that is not a whole number. |> |> CAT5 cable is an example. It has 4 different pairs twisting along. Each |> of the pairs has a different twist pitch by design (unless you get some |> cheap cable not manufactured correctly). | | Very interesting. | | Please can you advise on how these twisted pairs compare with | | 1. shielded audio cable | and | 2. rf coax. | | In case 1 both the wanted signal and the noise are in the audio frequency | range. | | In case 2 the electricity supply noise contains harmonics of similar | frequency to the wanted rf signal.
I don't have specific data on the quality of noise immunity. I'd bet that kind of research has been done. It most certainly would vary by quality of construction of the cables in question.
RF coax comes in various levels of quality based on a stated shielding percentage. I've seen lows of 60% all the way up to 100%. The latter could be a foil, or a solid metal encapsulation (quite a variety of different coax types with this).
I've seen cables, including CAT5, with both twisting _and_ shielding around the whole cable assembly. I don't know how much the effectiveness works together. I have not had a case where I would consider using it.

[snip]
: : I've seen cables, including CAT5, with both twisting : : _and_ shielding around the whole cable assembly. I : : don't know how much the effectiveness works together. : : I have not had a case where I would consider using it.
That's STP (shielded twisted pair) and is not really worth it for most applications. There is a military spec. for it somewhere, I believe.
It's also a different impedance to UTP so may not work correctly with all equipment.
Ivor

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All outside plant telephone cable with the exception of the local drop cable is shielded. Inside a telephone office equipment room, T1 and higher speed data cables are all shielded if the cable extends between rows or for more distance in one row than 4 racks.
STP is significantly expensive, and will not commonly be seen anywhere that it is not absolutely required. For example, it would make no sense to use it within a normal customer premise area, unless there is an equipment room with multiple rows of equipment racks.

Ivor Jones wrote:
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It should deal with hum pickup on audio cables quite nicely. However shielded twisted pairs are considerably more expensive, and you have to be careful about generating ground-loops in the shield grounding.
I replaced your non-standard (: :) quote markers with the normal '>'. Please don't use thos non-standard characters. They foul up other software.

: : 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

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Consider for a bit just how absurd that statement is...
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?
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.
What your formatting style does, is tell the reader what your priorities are, and that your ability to comprehend the effect is apparently impaired.

: : : : : 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

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

Ivor Jones wrote:
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Plonk

wrote: | Ivor Jones wrote: | |> |> With no respect, | | | Plonk
You should do that more often.

snipped-for-privacy@ipal.net wrote:
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I plonk for arrogance, not ignorance. You have NOTHING to worry about.

Ivor Jones wrote:
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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

[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

On Thu, 06 Mar 2008 16:04:57 +0000, Ivor Jones wrote:
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Third. But don't worry about me, because *plonk*

PCPaul wrote:
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The only problem with a straight plonk is that other peoples quotes of the plonkee shine through. The advantage of that is that one has a chance to decide the plonk should be retracted.

wrote in message : : : : : : : : [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. : : : : : : Third. But don't worry about me, because *plonk* : : : : The only problem with a straight plonk is that other : : peoples quotes of the plonkee shine through. The : : advantage of that is that one has a chance to decide : : the plonk should be retracted.
Indeed. But even three complaints in 10+ years (and I have my doubts on the validity of at least one of them) is not worth worrying about. I post a *lot* of articles on Usenet in 20+ groups, 3 complaints doesn't even register. 3000 might, or even 300. But 3..? Try harder.
BTW nobody has yet mentioned which piece of flaky software gets upset by a : instead of a >
Ivor