What is the Impedance of Antenna cable connected to a TV?

[manasiri]

connection matching

Dear friends,
I have 2 questions.
1- what is characteristic Impedance of Antenna cable that connected to an ordinary TV?
(Input impedance of TV????)

2- how I can connect an antenna or (N-type connector )to the TV.
(matching box??)

 

[vfone]

Re: connection matching

Input impedance of a TV usually is 75ohms and the feeding coax cable is also 75ohms.
You need an adapter between N-type connector and TV connector.
Can make your own cable adapter having N-type at one end and TV connector at the other end.
N connectors usually have 50 ohms impedance, but you can get N-type with 75 ohms impedance.
**broken link removed**

 

[biff44]

Re: connection matching

The difference in presenting 50 ohms or the correct 75 ohms to the TV input is probably not worth the effort of a matching network.

The voltage reflection off of your TV input is ρ = (50-75)/(50+75)= 0.2
So the voltage transmission into your TV input is T = 1 - (0.2²) = 0.96

in dB's, that means you will loose 20 Log (0.96) = 0.35 dB of power due to the mismatch.

It would probably be hard to find a broadband transformer for a 50:75 ohm match that had less than 0.4 dB of loss! So just jam it in.

It would be much more important if you were dealing with an older style 300 ohm antenna (300 ohm transmission line looks like two wires running parallel in a flat plastic sheet).