I've been looking at Laserdisc players, and I only recently realized that many Laserdiscs store digital sound. I'm thinking about getting a Pioneer CLD-D504 as it seems to go for a reasonable price and it has an RF AC-3 output, but I just realized that this kind of output isn't the same as the digital coaxial output used on most devices. What I want to know is this: Am I correct in think that you need something called an "RF demodulator" for a Laserdisc player like the CLD-D504 to work on a modern digital receiver? Also, exactly what does "RF" refer to and what does an RF demodulator do? Is it related to "RF" as used in reference to cable signals? If that is the case, then would a device that splits a cable signal into composite outputs do the same job as an RF demodulator?
RF stands for radio frequency. Just like the old RF A/V connection (mono audio channel/composite video) there are multiple signals present on one wire. You need a demodulator to separate these (two I think) signals from the single coaxial wire. These two signals are further demodulated by a AC-3 decoder. If your receiver has "RCA" style AC-3 input (using the red/white "stereo" connectors), the RF demodulator is all you need. The "digital coaxial output" you're referring to is called coaxial SPDIF, it's another way of modulating two or more channels digitally onto a single wire but entirely different than AC-3; AC-3 or any other sort of audio can be carried through SPDIF.
I thought that SPDIF used RCA connectors. My receiver has a RCA jack marked "coaxial" under the "digital" section on the back of my receiver. Using that jack I can listen to Dolby Digital and DTS sound from my DVD player. Is that SPDIF, or something else? Would I need something other than an RF demodulator to connect an RF AC-3 output to my receiver? Also, the Laserdisc player I was referring to has an RCA jack output for AC-3.
Yes the "coax" RCA connector is SPDIF. SPDIF can be transmitted over RCA connector or over the optical TOSLINK connector or even over a wire using TTL level logic. If your receiver can accept AC-3 over the defacto white/red RCA connectors (which it should), then all you need is the demodulator.
