You're conflating the tuner with the antenna. The person you replied to, however, is correct including the comment about the digital tuner boxes (which convert to an analog signal for old TV's) being available for free during the analog to digital changeover back when.

Any piece of metal will work as an antenna, even for receiving digital broadcasts. It might not work well, but there is no magical difference between a "digital" antenna and an "analog" one, and since digital television is transmitted over pretty much the same original frequencies as analog was, old analog antennae are already quite well tuned in size and shape to pick up modern digital signals.

You just have to plug your 1940's antenna into a 2009+ or so television. The antenna itself doesn't "decode" anything. It just catches radio waves and passes the waveform along to the TV or tuner box. I still use the old 60's era rooftop antenna that cane with my house, but plugged into my modern TV and it receives digital channels just fine.