2.4ghz propagation on standard residential coax between houses

AI Thread Summary
The discussion centers on the feasibility of using 75-ohm CATV coax for 2.4GHz signal propagation between adjacent houses. While RG6 coax has significant attenuation at higher frequencies, some participants speculate about the potential for transmitting signals like 802.11g through shared coax networks. However, it is noted that local cable networks typically convert coax to fiber optic at nodes, limiting the coax's range. Additionally, upstream filters are likely in place to prevent interference, making unauthorized signal injection illegal. Overall, while theoretically interesting, practical use of coax for 2.4GHz communication between homes is not viable.
mastafoo
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I know 75ohm CATV coax is anything but ideal for 2.4GHz, but I am still curious as to how far these signals will travel upstream through the existing local cable network (splitters, etc) laid by the cable company, and if they could be transmitted between adjacent houses on a street. Example: an AP is connected directly via F connector to the coax line at one house and client at a nearby house connects to their coax, allowing Tx/Rx completely through the cable. Surely several hundred milliwatts should be able to push through.

Thanks
 
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The attenuation of RG6 cable at 2 GHz is about 7 or 10 dB per 100 ft if I remember correctly. These cables are used extensively for home satellite TV which works by taking a chunk of 1 GHz to 2 GHz IF signal from the LNB converter at the dish to the satellite receiver in the living room.

Edit:
And as far as the local cable network is concerned, the main coax feed which splits to houses in a neighborhood is converted to a fiber optic line at a node. It is the fiber optic that eventually makes its way to the cable company which could be many miles away. So the coax itself doesn't get very far from the house anyway.
 
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waht said:
snip

Edit:
And as far as the local cable network is concerned, the main coax feed which splits to houses in a neighborhood is converted to a fiber optic line at a node. It is the fiber optic that eventually makes its way to the cable company which could be many miles away. So the coax itself doesn't get very far from the house anyway.

interesting... wonder where you live ? and how new the network is ?

I'm in Sydney , Australia and there are 2 maj cable networks by 2 of the maj comms companies. They ARE cable all the way from source to customer.

I don't bother with cable TV jst a waste of money, but I do get my phone and internet service over that cable network. I havent, as yet, discovered what the freq range is used for the network.

cheers
Dave
 
I subscribe to cable internet and TV (comcast), and have reason to believe that my node is shared between a hundred or so houses in the neighborhood. In that case I guess it could be possible to use this coax between the houses to send signals (802.11g or maybe video). I'm just not sure if there are any upstream filters or anything like that installed which would attenuate the signals, or if 75ohm rg6 will even match wifi cards' impedance
 
davenn said:
interesting... wonder where you live ? and how new the network is ?

I'm in Sydney , Australia and there are 2 maj cable networks by 2 of the maj comms companies. They ARE cable all the way from source to customer.
I don't bother with cable TV jst a waste of money, but I do get my phone and internet service over that cable network. I havent, as yet, discovered what the freq range is used for the network.

cheers
Dave

In the US, most of the major cable companies are running huge fiber optics networks to service large metropolitan areas. Those fiber optic cables begin at the headend and end at a node in some neighborhood (although there are some exceptions). The node is just a small box hanging at a pole, or could be accessed underground, where it converts the lightwave from a fiber into an RF cable signal between 50-850 MHz downstream, and 5-40 MHz upstream. The coax cable is then split multiple times and can service 500 to a few thousands customers at a time.

mastafoo said:
I subscribe to cable internet and TV (comcast), and have reason to believe that my node is shared between a hundred or so houses in the neighborhood. In that case I guess it could be possible to use this coax between the houses to send signals (802.11g or maybe video). I'm just not sure if there are any upstream filters or anything like that installed which would attenuate the signals, or if 75ohm rg6 will even match wifi cards' impedance

It's not possible to do that. Upsteam for Comcast ends at about 40 MHz, and it sure is filtered. And also, it's illegal to tamper with their networks by injecting a foreign signal into it.
 

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