RF DC-Blocker / Switch

Hi,

I have a TV tuner which on one side is connected to the cable TV.
The TV tuner is just something I bought in the market, but I'm moreover interested in the circuit.

I would like to add a switch which allows to choose between the RF signal which comes from the cable provider and a normal antenna. The switch will change the signal path to the antenna if 5V 20mA is applied.

I have access to the GPIO lines of the usb stick (which output 3.3v or 0v), so I would like to be able to toggle that RF switch through software using those gpios

Now the question is how could I apply those 5V in a switchable way to the antenna output of the USB Stick without applying that voltage on the tuner chip directly? (I guess I need a dc blocker for that).

Can anyone guide me to some more information about that, what keywords I have to look for?
I would like to understand how that works.

ok I'm a little bit further with this, I need some kind of dc block capacitor eg. 3.3pF? can someone guide me to some equation how to calculate the right value?

A DC blocking capacitor doesn't need calculating - it just needs to block DC.

You simply need to consider the frequencies it's passing, and the impedance it's working at (usually 75 0r 50 ohms).

1000pF would be a pretty common choice, and would easily cover both UHF and VHF.