This is a very good question, you can also ask such questions. If you want to connect the old TV to today's set-top box then here you will get the answer.
OLD TVs -
Older TVs do not have audio video (AV) ports. They have an RF port. Black & White TV is also mainly included. But these TV sets are unable to receive signals using an AV port.
New Set-top boxes -
But the problem is that the set-top boxes that come these days do not have an RF port, due to which people's old TV has become useless.
What is the solution?
The only solution is that you need to buy an RF Converter or RF Modulator to convert audio video to RF. RF modulator allows converting your AV input to RF output signal
You can ask for this AV to RF Converter or RF Converter from online or offline shops.
If you have any other questions related to DD Freedish settings then you can ask through comments.