The correct value of course...
Ba da boom...
Twisted pair will be dependent on insulation thickness of course. It's easy to get within 2 to 3% of the terman value if done right for 20 to 100 foot lengths.
How old is that meter now?
What you should be doing is build a test bridge to look for proximity eddy loss distortion. You like doing that kind of thing.
Two lengths of 100 foot, terminate each at 8 ohms, use another pair of 8's to complete the bridge.
Left half cable high resistor low, opposite on right half..analyzer across middle.
Then detail to us what the harmonics are...I am patient....not retired yet (although some presentations are claiming that I am close to it..)
Jn
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When you start claiming to measure distortion down to -170dB as Ed likes to do you will need to control environmental variables like mains hum and buzz, high frequency switching noise and PWM fan speed controller noise you will like the looks of my NEMA Type 1 enclosure a lot better.
Thanks DT
Please no offense intended, ferrous metals have eddy current distortion easily measured it has nothing to do with shielding. I have measured and published a note on it, an air-core inductor / film cap filter had distortion when even a pair of diagonal cutters came close let alone putting it on a steel lab bench.
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Do you have the ability to measure Ls/Rs vs frequency? It is very important to do so, as it is not easy to partition out the inductance from base reactance. Most meters just measure the phase shift between voltage and current for L (or C), and do not decide which part is L or C.
By scanning frequency, the base geometric inductance is the asymptotic value as you go down in frequency. The plots of Ls and Rs will be well behaved within a range of F.
Also, most meters will simply call all out of phase energy the L (or C), and everything else as Rs. All third harmonic energy loss in the tested system is considered Rs, the meters are not smart enough to separate eddy loss harmonics from simple Rs.
That is what you should look for in a bridge test.
Jn
A 2-wire RF rejecting twist?tapestryofsound said:
I can see air gaps between your wires. Gaps increase RF pickup. My guess is that it is harder to avoid all gaps in plaiting. Also, my guess is that a plaited cable needs a longer piece of wire than twisted (does anyone know?) so will have slightly higher resistance.
Anyway, the only place plaiting is used in real engineering is for low inductance flexible ground straps. All the wires are connected in parallel.
Thank you for wisdom in real electronic engineering - looks like I am doomed. ToS
Beautifull wire plaiting was done in "Honey comb coils"
Honey comb coils and how to make them: Dutch Amateur Radio Station PA2MRX.
Honey comb coils and how to make them: Dutch Amateur Radio Station PA2MRX.
For domestic audio if you like the look and you put real effort into making it that gives you enough happy hormones to improve the experience.
How very true Bill.
Every time I fire up the horn speaker, and see that lovely cable sneaking its way across the floor, all loaded up with musically charged electrons ready to burst out with unbridled sonic happiness, I realise my humble life is complete.
ToS
Ed.
I have re-thunk what we are discussing.
A twisted pair cable wound randomly on a spool should read as unspooled.
I realized you never have a 1000 foot spool of #10 twisted pair cable that is random wound (just looked at some spools of 535 kcmil).. Rather, you get it with uniform wind with perfect lay on each layer.
While it is "said" that twisted pairs do not couple, they indeed will couple to another twisted pair that has the identical pitch (or an integer multiple). So, on a single layer, it is very possible that a cable will couple to itself, depending on the twist pitch, the layer diameter, and the insulation total thickness.
As purchased, it is not possible to determine how much coupling occurs within the spool, so we can't determine the true values on spool.
Also, simply off-spooling some and sending it to me for verification, I would test a random wind coil and can end up with different values from that measured on spool. Also, removing one layer from the spool can change what the spool measures per foot.
jn
I have re-thunk what we are discussing.
A twisted pair cable wound randomly on a spool should read as unspooled.
I realized you never have a 1000 foot spool of #10 twisted pair cable that is random wound (just looked at some spools of 535 kcmil).. Rather, you get it with uniform wind with perfect lay on each layer.
While it is "said" that twisted pairs do not couple, they indeed will couple to another twisted pair that has the identical pitch (or an integer multiple). So, on a single layer, it is very possible that a cable will couple to itself, depending on the twist pitch, the layer diameter, and the insulation total thickness.
As purchased, it is not possible to determine how much coupling occurs within the spool, so we can't determine the true values on spool.
Also, simply off-spooling some and sending it to me for verification, I would test a random wind coil and can end up with different values from that measured on spool. Also, removing one layer from the spool can change what the spool measures per foot.
jn
Being fascinated by audio as sculpture, I just love what is in this link - thank you for making the day brighter. ToS
JN,
The way I see it is I measure it straight and then coil it with cable ties. You then measure it as received and then straight. That way we can see if we agree on the basics.
BTY the original breakthrough in inductively tapping telephone lines was that the twist for each pair is different, so different twist inductive couplers could isolate individual pairs. Worked! Unfortunately, the East Germans were tipped off by the tunnel workers.
The way I see it is I measure it straight and then coil it with cable ties. You then measure it as received and then straight. That way we can see if we agree on the basics.
BTY the original breakthrough in inductively tapping telephone lines was that the twist for each pair is different, so different twist inductive couplers could isolate individual pairs. Worked! Unfortunately, the East Germans were tipped off by the tunnel workers.
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