Twisting wires for heaters

[Mark]

When I was in college we were studying CAT10 cables and working out the twist rate needed to get the best results. I remember doing calculations for 50Hz and I was surprised at how loosely the twist rate needed to be.

Unfortunately, I can’t find any info on this sort of thing, all I get is the twist rate for bullets leaving a barrel.

Can the smarter folk here add info to this topic?

Thanks for your assistance.

[Stevem]

Interesting!

I never new these was such a thing/ ratio.

Marshall out of all the brands I have come across over the decades seems to do there's very loose, like around 1 twist per 3/4".

Whenever I up grade a amp or build one I twist them as tight as I can, maybe I should not

[martin manning]

I have seen 6 turns/ft quoted for magnetic field shielding. Over-twisting is pointless, and could cause lead breakage.

[R.G.]

I was aware from our fields courses in college that the twist rate was critical for RF wiring, but they never did an example for line frequency. I think that the fact that heater wire is twisted at all overshadows the exact twist rate.

For high frequencies, you're messing with characteristic impedance and matching to keep reflectances, radiation, and transmission losses low. I think that for line frequencies, the primary issue of concern is electrostatic and magnetic field leakage. Both of these are minimized by having the wires as closely parallel as their insulation will allow. twisting the wires is a handy way of having the wires keep themselves as close to one another as possible. The electrostatic fringing field is minimized by the proximity of the wires, and the M-field has the smallest possible loop area, both of which keep the respective fields between the two wires, not spreading out into the space around the wires.

I would have to go look up the equations too, but I think the fact that it's twisted just tightly enough to keep them together is fine. A twist every inch or two is probably all that's needed.

[xtian]

I often employ short lengths of shrink wrap tubing to keep heater wires side by side.

[didit]

Hello Martin --

I have seen 6 turns/ft quoted for magnetic field shielding. Over-twisting is pointless, and could cause lead breakage.

Yes, in metric a 5cm twist for common mode suppression. Purely for physically stable preamp string wiring my tendency has been a pair 20awg stranded twisting quite a lot tighter, and then raised above perhaps 3 cm off sockets. If done cleanly seems to then provide enough space for signal soldering, even for sequence of repair and/or proto-mod of components etc. Work method preference with nothing to do with theories on noise avoidance.

..

[trobbins]

Some refs on the topic:
https://dalmura.com.au/static/Predictin ... Cable.pdf
https://dalmura.com.au/static/Reduction ... twist.pdf

[Mark]

Thanks for the replies and links I appreciate it. I think some people think the tighter the twist the better but I don’t think the data bears that out.

[trobbins]

What data were you assessing to come to that view ?

[Mark]

What data were you assessing to come to that view ?

I’m not sure who the question is directed to.

[sluckey]

What data were you assessing to come to that view ?

I’m not sure who the question is directed to.

Gotta be you since you're the only one to use the word "data" in this thread.

[Mark]

What data were you assessing to come to that view ?

I’m not sure who the question is directed to.

Gotta be you since you're the only one to use the word "data" in this thread.

Yeah, but I point out in the first thread that I no longer have access to the data but I have seen it and I can’t find it on Google search. The trobbins did kindly provide links to information, so I’m not sure who he is referring to.

[trobbins]

Mark, your first post indicated cat10 info, and that you recall doing calculations. That didn't sound like data, which is why I asked.

There are a few academic/journal papers on the topic over the decades, but many require access. I recall another paper that went to measurement data on twist rate, but couldn't find it. However I'd say the 'data' afaik says twisting, and with a closer pitch (or. thinner insulation and as small a gauge as practical) is better, but every emitter needs a receiver to become a problem, and many just use their ears, so for most it is a non-issue until their layout/application makes it an issue.

[wpaulvogel]

I have seen 6 turns/ft quoted for magnetic field shielding. Over-twisting is pointless, and could cause lead breakage.

It also puts more copper mass in the circuit. The important factor is parallel wires and a light twist keeps the conductors together for suppression. Using a drill to make candycane puts unnecessary wire into the circuit and has no positive impact. It also makes connections to the sockets more difficult.