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A: Satellite signals are a totally different use case to normal data, operating at a very high frequency, which is very inefficient.
B: There is no such thing as Category 7 cable.
Moving virgin/telewest cables
- Thread starter houstonwehaveaproblem
- Start date
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A: Satellite signals are a totally different use case to normal data, operating at a very high frequency, which is very inefficient.
B: There is no such thing as Category 7 cable.
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A: I never said they weren't, but a fully shielded coaxial cable was the first copper option for 10GE, (CX4), and 10G over twisted pair took years longer. Copper 40G is co-ax too (but that's cheating as it's really 4 10G links aggregated).
B: Quite correct, I was loose in my terminology. The cable is ISO 11801 Class F (or more expensively and higher frequency rated FA), though ISO 14165-114 does refer to Class F as Category 7 cabling.
That aside, class FA (or Cat7A) runs up to 1000Mhz (standard) or 1200Mhz (certain reputable manufacturers) , and co-ax can go plenty much higher than 100 times that.
In any case, satellite over fibre is the way forward for the application I have. I just need someone to develop a PCIe card that'll take a whole LNB feed, demultiplex, and extract a listed of PS's from the TS's to allow me to spit them multicast out of a 10GE, so that I don't have to demultiplex the fibre, then 4->24 distribute, and have a half-rack of boxes full of tuners.
Coax is a conductive core surrounded by a conductive outer layer. The relative sizes of the core and outer set the characteristic impedance of the coax while the properties of the insulation, the tolerances used in the manufacturing process and the length of the run set the usable frequency range.
You can't really compare "twisted pair" and "coax" in general because both are broad categories of product so lets compare the best grade of each in common domestic use. That is CAT6 VS WF100. From a quick searh it seems CAT6 has a loss of about 30db per 100 meters at 200 MHz while WF100 has a loss of about 30db per 100 meters at 2 GHz. So it's pretty clear the WF100 has far more usable bandwidth even accounting for the fact the cat6 cable has four pairs.
I'm pretty sure CX4 actually uses a twin-axial cable which is an attempt to combine the best of twisted pair and coaxial in a single cable.
Some specialist coaxes have a usable frequecy range that high but they are bloody expensive and still relatively lossy.
BTW it is meaningless to speak about bandwidth without also speaking about loss. Cables don't really have a hard edge to their frequency range they just get lossier and lossier as frequency increases.
Which is a fully shielded co-axial cable, albeit with a pair of conductors. My understanding of twinax is that the centre conductors aren't twisted though.
At getting up that high, one starts talking about waveguides, and find that because the skin depth is so small, the stuff's generally hollow, which saves copper, but causes other fun at installation time.
That indeed. I *could* run up to 2150Mhz over 20m of Class FA if I could live with over 100dB of loss. Given that I can't, I have to use coax.
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I dont know how widely used the term is in the elec industry but it hydraulics this type of hose is refered to as siamese hose and it appears from a quick google siamese cable is a valid term.
I have moved BT sockets once or twice, not recomended or allowed by BT but with care it does no harm.
Daniel
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Wow all rather technical for me! 
Strangely, "siamese" refers to a pair of cables, which are NOT identical. One usually carries power and no signal.
"Twin" or "shotgun" refers to a pair of coaxial cables, which ARE identical.
"Twin" or "shotgun" refers to a pair of coaxial cables, which ARE identical.
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Shotgun is one coaxial and one 1mm power pair to me.
Shotgun WF65 http://www.satcure.co.uk/accs/page8.htm#WF65 so-called because it looks like a shotgun twin barrel from the end.
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Try installing that for a Sky+ customer.
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Try installing that for a Sky+ customer.
Just showing the differences between the same names.
However my sons could run cables better than Sky installers.
I'm sure they train with lasso`s.
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