This will accept an HDMI input and output to channel 3.
https://www.amazon.com/HDMI-Converte...s%2C148&sr=8-7
or this is you already have an AV to RF convertor around...they're everywhere. I'd probably go this route anyway and buy an RF convertor.
https://www.amazon.com/Converter-Ada...xpY2s9dHJ1ZQ==