It is possible to use your existing cables to watch Freeview, but this is dependent on the condition of these cables. They need to be in good condition for them to work.
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Faulty cables are unable to transmit signals efficiently; when uncertain, it's advisable to replace them. Cables are readily available at numerous electrical retailers for your convenience.

To find out more about your cables and aerials when watching Freeview, please take a look at this article.