How about a TV matching transformer for a balun?

[beltane]

I was wondering if I could use a TV antenna matching transformer as a balun for a dipole antenna on an HT, say 5w max. I don't know what's inside them but basically they're a balun, right? It isolates one end from the other. I wonder if it would stand up to 5w.

[ch25]

Better not. Those are not meant to be used for transmit.
Ferrite core might be wrong material etc.
Use choke balun instead or proper ferrite balun.

[Buick Mackane]

A matching transformer and a balun are two different things, A matching transformer converts impedances, For example a 49:1 transformer converts an impedance of 2450 ohms to 50 ohms, A balun converts a balanced antenna like a dipole to an unbalanced feeder (coax) AKA a 1:1 transformer