Broadband - Data, Radio and Television by Cable

Coaxial Cables are usable over a wide Range of Frequencies, so one Cable can be on duty for 2-Way-Data (for example Internet), classic Radio and Television. But the higher Frequencies are the shorter is the Distance which they can travel over electric Wires before they need to be amplified on the Way. So Broadband-Service mostly starts via optical Fibres and it’s transfer to Copper Technique is done once close enough to the Customer. Let’s skip the Beginning and only have a closer Look what can be done using the Coax.

The typical Frequency-Blocks are (in MHz):

As You see there are Areas that overlap, or might make Problems then used at the same Moment.

Band I so is normally not used on Cables where an Data-Upstream is available, to gain a comfortable Gap between Signal Directions. Sat and Extended Up-/Downstream are also Things that overlap, and so urge a Decision what to use (at least where).

The 3-Outlet Data + Radio + TV Socket does not allow to add Satellite TV to what the Cable-Company delivers. Typically (at least) on Data You will get 5-65MHz + 125-862MHz, on FM-Radio 87,5-125MHz and on TV 125-862MHz.

A 4-Outlet TV- + Sat-TV- + Data- + Radio- Socket might better fit to Your Needs, as it allows (by the use of a proper Switcher/Broadband-Amplifier) to add Satellite TV to what the Cable-Company delivers. Typically (at least (*)) on TV You will get 125-862MHz, on Sat "DC"+950-2150, on Data 5-65MHz + 125-862MHz +(maybe) 1250-1950 & 2259-2950MHz and on FM-Radio 87,5-125MHz. (* There is a high chance that in Fact all Outlets cover the same Range (except that DC will only find it’s Way via the SAT Socket) and are mainly just different by Connector-Type.)

Cable-Modems reach 43000kbit/sec Downstream and 10240kbit/sec Upstream, while it depends on You Cable-Company what’s Your personal Limit for using the shared Medium. It’s a myth that the Cable-Network has to be extended to 850MHz to allow Internet-Access via it, but when working on enabling Upstream it is just logical to do the Step to a wider Frequency-Range in the same Moment. Then You just want to get Internet + TV from Your Cable-Provider, and he is really offering it in Your Area, all You need is an Uplink enabled RF-Amplifier (if You need an Amplifier) and a proper Outlet Socket. Ok-ok, if Your cables are too old, or where ruined, they have to be changed too, that’s why many Cable-Companies warn You from the beginning about that, or even generally mount new in-house cables when at work.   Then You see that there is Use of Coaxial Cables for Data-Purposes You might have the Idea that this could be the Solution of Your personal Network Problems. As the Data-Directions are run on different Frequency Bands it is clear that You will have to buy more than just Cable-Modems. You need a Counterpart for them: a “Headend Broadband Access Router", that receives there the Modems are transmitting and is transmitting there the Modems are Receiving. And, for sure, You want a symmetric Bandwidth, as 10240kbit/sec Upstream, 43Mbit/sec Downstream in Your Case means that Your Network can only reach a typical 10Mbit/sec-Ethernet Participant<>Participant Speed, while You would prefer something that is closer to 100Mbit/sec. Let’s hope that at least one Hardware-Company offers a Cable-Modems and Counterparts for them that allow to set up private Networks that are symmetric, with at least 43Mbit/sec. The Setup there a Cable-Company offers Internet-Access via Cable, while You have your own LAN already up on Your own coaxial Cable, would be Cable-Company == Cable-Modem <> Firewall/Router <> Private Headend === Cable-Modems. This means that it is no real Problem to use the Coaxial Cables for Private Networking while there is also a Cable-Company that offers Internet-Access via TV-Cable. All You have to take care about is that Uplink-Signals of Your Inhouse Modems will only reach Your private Counterpart for them, not Your ISP’s. And that is really easy to achieve by the use of a cheap (not uplink enabled) RF-Amplifier and a Notch- Filter at right point. This System, of having an own Headend-Router might even be the cheaper solution, as it could allow to keep your own big Sat-MultiSwitch on duty, with just ‘minor’ adds, when getting Internet-Access via your Cable-Company.

http://KarlKramer.de/tips/Network/Cablemodem.htm ©14.July 2002 Karl Kramer