Thread: Noise on Cable and DSL Networks
View Single Post
Old 13-08-2006, 20:12   #4
James Henry
Permanently Banned
 
James Henry's Avatar
 
Join Date: Apr 2006
Posts: 562
James Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these partsJames Henry is just so famous around these parts
Re: Noise on Cable and DSL Networks
Quote:
Originally Posted by jtwn
Thankyou for your explanation and confirming my statement.

Do note I did say 'its transparent to the end user to an extent', to an extent as I don't know why you would think I would not realise a ****ty line would mean problems. I didn't say transparent to cable end of sentence.

Its a nature vs problem scenario. Noise on ADSL lines is nature, where noise on cable is problem (to be fixed).
Why would I have wanted to split hairs when you do it yourself? 'To an extent'. I could stick my own testicles in a vice, wind it shut and it would be painful 'to an extent'. Doesn't really mean much is a way to avoid quantising things.

Onto the rest of it.

Anyone who knows what they are talking about knows that noise is a fact of life and expected on cable networks as well.

Excessive noise is indicative of a fault on both platforms.

May I suggest you do some research on amplification. Maybe look into push-pull amplifiers, composite second order distortion, composite triple beat, common path distortion, intermodulatory products.

If you actually knew what you were talking about you'd know that the 'lining up' of HFC networks is a balancing act between power levels and distortion. In addition to this 'noise 'ingress from external sources is also both expected and allowed for in the SCTE specifications for cable networks. Oh and yes, distortion is considered 'noise' - cable networks by nature introduce 'noise' onto the networks themselves.

It's the balancing act between noise and distortion that was a major driver for HFC networks to replace pure coaxial networks. Reducing the number of amplifiers in a cascade results in a larger operating margin between power being too low, meaning noise floor - the noise caused from a combination of amplifier / optically induced distortions and ingress from external sources causes an unacceptable CNR (that's Carrier to Noise Ratio which you may not understand as your modem doesn't have it listed on its' diagnostics, google it) as it's too close to wanted signal for power, and amplification introducing unacceptable levels of distortion onto networks resulting in the noise floor being raised too high.

Cable networks course closed for this evening.
James Henry is offline