Length important?

[#1]

Does the length of the cable from the router/modem
affect the performance of any hardware attached to it?
The longer the cable from the source, the weaker the signal
received by the TV/switch/etc?
Is there a formula to assess the signal weakness use to or is
there no signal loss whatever the length of the cable?

[#2]

Length of cable from Telephone exchange to Green box, to your house... makes a difference .... 

[#3]

If you are talking about the length of the Ethernet cable between the router and one of your pieces of equipment then yes the length is significant - but unless you live in some sort of mansion or you are running a cable to an outbuilding at the end of a very, very long garden you are unlikely to hit the limit.
Up to 100 meters (328 feet) there will be no issues and no loss of speed. Beyond that you are out of spec.

[#4]

it rather depends on the standard of cable you use more than anything else, a fully shielded cat5 or cat 6 then up to 100m should be lossless, unshielded than anything over 25m is liable to problems unless you have inline signal boosting, I used to work in an office where the port replicator was 75m from the port we were using, the contractor used unshielded cable and every time someone switched on a mains powered item in the room next door the connection would go dead until it got switched off...... took the network installers 2 years to figure out the problem because they didn't know the wrong type of cable had been used /

[#5]

Quote from: spoon

Up to 100 meters (328 feet) there will be no issues and no loss of speed. Beyond that you are out of spec.

Presumably a switch at the end of each cable (which would recieve and retransmit the data packets) would work well to keep the signal going?
Failing that i suppose its a fibre connection..