I recently pulled two 800 foot pieces of LMR 900. Those were some honkin spools. 1200 feet per. The spool size is somehow linked to the tightest radius of curvature the manu recommends for the coax, we have real concerns about that as we load it into the cable trays.
jn
Cat5 requires a minimum radius to stand a chance of meeting specification.
Minimum bend radius probably applies to all HF cables.
Minimum bend radius probably applies to all HF cables.
Cat5 is 8X to 10X the OD of the cable (though I have seen smaller figures), coax if over bent can cause quite a severe impedance discontinuity as the geometry can change between the inner and outer cores. Another tip is put your cable real on an axle and always pull the cable of straight, never uncurl it as this put stresses in the cable.
We used 2 jack stands and a big pipe. Standard setup for the big reels.
There is also the worry of signal spillage. Bent too much, the outer sheild goes oval, so stops full cancellation of the inner core magnetic field. That raises inductance and impedance, reflecting and broadcasting at the same time. We have lots of other cables which rely on not picking up spurious signals in the vicinity.
I had to explain to the muscle how delicate the coax was, like a brake line..bend too much, it kinks.
Oh, and to the physicists, why you shouldn't put 4 pieces of 1/2 heliax running 500 watts rf in the same conduit as 3/8th heliax low level signal cables. Especially since the conduit makes two 90 degree bends.
jn
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To a physicist a coaxial cable is coaxial. If it is coaxial then it won't create or receive interference. If it isn't coaxial then it isn't a coaxial cable. We physicists have simple brains! We like symmetry so assume it whenever we can. Failing that, the next best things are small perturbations from symmetry or spontaneously broken symmetries.
The issue with installing thick coax cropped up with early Ethernet in power stations. Electrical fitters assume that all thick cables are equally strong and equally able to cope with tight tiewraps to a cable tray and sharp bends.
The issue with installing thick coax cropped up with early Ethernet in power stations. Electrical fitters assume that all thick cables are equally strong and equally able to cope with tight tiewraps to a cable tray and sharp bends.
The wire pullers had a wide range of things they had to pull, so it was necessary to remain ahead of them. They had to pull 2 kilometers of 535 kcmil, lots more 373, 262, 4/0 sizes. Then #6awg/4, 8/2, 14/4, 10/4, multiconductors. Then fiber, from 72 strand multimode down to itty bitty single modes 400 meters long. In that mix, toss in the heliaxes in .240 to .9 inch dia. A really interesting combination of muscle and finess at various times. Heliax that looks like you could tow a truck with but need delicate handling, fiber that'll break if you sneeze, then 1000 foot spools of 1.3 inch diameter "suspension bridge" cables.
jn
We use a lot of coax, triax and fiber at work. We do try to be careful, but show biz being what it is.... I'm routinely amazed at how much abuse it can take and still pass signal with no noticeable degradation.
I know it's OT but, I used to be a bit of a radio ham, I got bored with the constant discussions about aerials though and packed it in some 25 years ago now.
I well remember the effect of replacing 22 metres of standard coax with a heavy low loss version. The effect was not subtle to say the least, it brought a huge improvement in transmission and reception.
Since then I have believed that signal cable types do matter - but they are not worth obsessing about 😉
I well remember the effect of replacing 22 metres of standard coax with a heavy low loss version. The effect was not subtle to say the least, it brought a huge improvement in transmission and reception.
Since then I have believed that signal cable types do matter - but they are not worth obsessing about 😉
Would that be 'huge' in the audiophile sense of the word i.e. barely perceptible? Or was this moonbounce?davym said:
For radio, signal cables matter. For audio, they don't. (within reason, of course).
It was a huge difference. The tiny signal voltage involved in reception is especially handicapped by using a lightweight cable at those lengths. It is not difficult to see the difference it makes in radio when you have an accurate signal strength meter.
I also find that the phrase 'huge difference' in audiofool terms, somewhat challenges the meaning of the word, huge 😀
I also find that the phrase 'huge difference' in audiofool terms, somewhat challenges the meaning of the word, huge 😀
It was a long time ago so I don't remember who made it but it was 50 Ohm cable with a single heavy screen and it was aprox 10mm outer diameter.
For audio I mainly use this stuff nowadays along with neutrik phono plugs, it seems to do a good job - http://www.amazon.co.uk/SHOTGUN-INTERCONNECT-2x2-5mm-SPEAKER-12x4mm/dp/B0071Y3PAK
I also have some Shark silver coax wire which I made into interconnects. I am using some of that stuff from my tt to preamp, it appears to sound more open than the copper stuff does, the tiny signal from my mc cart seems to benefit from it somehow.
For audio I mainly use this stuff nowadays along with neutrik phono plugs, it seems to do a good job - http://www.amazon.co.uk/SHOTGUN-INTERCONNECT-2x2-5mm-SPEAKER-12x4mm/dp/B0071Y3PAK
I also have some Shark silver coax wire which I made into interconnects. I am using some of that stuff from my tt to preamp, it appears to sound more open than the copper stuff does, the tiny signal from my mc cart seems to benefit from it somehow.
75 ohm digital cable, reasonable quality will do the job.
Has the layout to the cable been optimised so all the routes are 75ohm, nope, the RCA connectors are not true 75 ohm and as many have pointed out having an exact 75 ohm impedance is not that critical for SPDIF (it would be nice) anywhere near will do, +/- 20% will not give any noticeable difference.
RF is different from digital signals a lot different you cannot make parallels or compare the two, two different areas of electronic engineering so what causes HUGE differences in RF will not even be noticed by digital signals.
Has the layout to the cable been optimised so all the routes are 75ohm, nope, the RCA connectors are not true 75 ohm and as many have pointed out having an exact 75 ohm impedance is not that critical for SPDIF (it would be nice) anywhere near will do, +/- 20% will not give any noticeable difference.
RF is different from digital signals a lot different you cannot make parallels or compare the two, two different areas of electronic engineering so what causes HUGE differences in RF will not even be noticed by digital signals.
That cable is not speaker cable, although the range also includes speaker cable. Amazon are confused.
The spec says <97pF/m. Foam will give velocity factor around 0.8, so I calculate an impedance > 43R. So it is unlikely to be 75R, but could (just?) be 50R. OK for short runs of SPDIF as digital audio is robust - evidence that this thread is on a wild goose chase.
The spec says <97pF/m. Foam will give velocity factor around 0.8, so I calculate an impedance > 43R. So it is unlikely to be 75R, but could (just?) be 50R. OK for short runs of SPDIF as digital audio is robust - evidence that this thread is on a wild goose chase.
Is that not the case with all cable threads, sooner or later.
I use the van damme interconnect cable - surprisingly as interconnects.
I also use van damme speaker cable, as speaker cable 😀
I could try using fence wire, but I might get domestic grounding issues 😉
I use the van damme interconnect cable - surprisingly as interconnects.
I also use van damme speaker cable, as speaker cable 😀
I could try using fence wire, but I might get domestic grounding issues 😉
I just use type 2 Litz wire for everything. When I used it for SPDIF cable I just added shrink tubing sections until the dac and player synced up. I don't think I could tell a difference between the Litz and a Radio Shack incandescent orange 50 ohm cable, but the color offended me.
Jim Brown being both the AES committee chair on EMI/RFI and a Ham radio operator, has several papers that touch on co-ax for Ham radio stations.
Audio Systems Group, Inc. Publications
Start with:
'Some Q&A About Coax and Stubs for Your HF Station'
By Jim Brown K9YC
Second Edition – October 2011
Q: What do I look for when buying coax for my HF station?
http://www.audiosystemsgroup.com/Coax-Stubs.pdf
Audio Systems Group, Inc. Publications
Start with:
'Some Q&A About Coax and Stubs for Your HF Station'
By Jim Brown K9YC
Second Edition – October 2011
Q: What do I look for when buying coax for my HF station?
http://www.audiosystemsgroup.com/Coax-Stubs.pdf
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