Before DisplayPort and HDMI, S-Video and RCA, the only way users could connect a device to their television was through the RF input. Besides struggling with poor-quality cables, there was also a lurking enemy in interference, and as if that weren't enough, you could only choose one of two channels, 3 and 4. Why those channels? VWestlife explains it in his latest video.
At some point in the '80s, I was first exposed to a generic (and not at all official) version of the Atari 2600. Almost immediately I had to learn its technical quirks, starting with the differences between NTSC and PAL (at first I could only play in black and white), and the need for an RF switch to switch from the console to the traditional antenna.
Why? Because it was the only connector available, and suddenly there were several devices claiming its “attention”. Added to that was another requirement: On the console we had to choose one of two channels, 3 and 4, or 2 and 3 in some isolated examples. Why only those channels? In his latest video, VWestlife shares the details that led to that selection:
Resolving the mystery of channels 3 and 4 on consoles
As expected, this responds (to a large extent) to the technical conditions of each region. “The Americas” use the same section of the VHF band to set up their channels 2 through 13, but not everyone knows that that section is also divided into two parts: VHF Low (2 to 6) and VHF High (7 to 13). In fact, for a long time it was quite common to see two antennas on the roofs of houses, optimized for VHF-L and VHF-H.
This is where the cost factor comes in: Higher frequencies demand more complex hardware (and better tolerances), as well as thick cables with robust insulation. By focusing on VHF-L, both consoles and modulators were able to adopt simpler components and use thin cables.
So… why 3 and 4? If we analyze the old channel allocation in many US cities, we'll find that the 'freest' channels, so to speak, were 3 and 6. However, channel 6 has a small overlap with the FM band, between 87 and 88 MHz. That only leaves channel 3 as optimal, and channel 4 (or 2 on other devices) simply serves as backup, in case there is a local station.
