How is this done? Do they make a selector for the old consoles, or do you have to buy a couple of $30 radio shack coax to rca adapters?

Your post is very unclear, but if you're asking how to connect an old console with an RF connection to one of those RCA-type switchers, the answer is you can't.

You cannot just get a coaxial-to-RCA adaptor, because the output from RF and input for composite video are not directly compatible.

You can't get a $30 RF modulator, because that converts RCA composite video to RF, not the other way around.

You can either hook up the RF cable to the antenna on the TV and suffer the lower picture quality (although for 8-bit, who really cares), you can buy a composite or s-video cord for the console if available (probably not, for 8-bit systems), or you can find a pricey way to convert RF to composite (RCA). The easiest way to achieve this is to run the RF into a VCR and use the VCR's RCA outputs, but that seems like a lot of trouble.

That is what I sant to do, but it sounds like I might be SOL. I'll have to keep thinking.

Could you just screw them into each other? For example screw the SNES one into the TV, the Genesis one into the SNES one, and then the TV cable into the Genesis one?

It's been so long (NES) since I used RF cables that I can't recall if I ever tried it.

I'm sure it would degrade the quality some if it works at all, but the quality of RF is pretty poor anyway.

Yes you can. I did this when I had both my Genesis and NES hooked up. Didn't notice a drop in picture quality. I'm actually going to be doing this again, because I'm hooking up my Genesis/NES/TG 16, once I get an AC adapter for the TG16, which is a pain in the arse to find......

I had this same problem recently. I have an older TV that has no bells or whistles (multiple inputs, composite inputs, S-video, component inputs, etc)

I also have an Atari Jaguar, Atari 2600, 8-bit NES, Odyessy 2 ('till it recently died...sob), Dreamcast, PS2, DVD player, and 2 VCRS.

I basically pipe *everything* through my primary VCR into the television.

For the coaxial stuff (Jaguar, 2600, NES, ODY), I feed all of them along with my cable TV into a coaxial switchbox. The output of the switchbox gets hooked to the coaxial input on my primary VCR. Hence, if I want to watch cable TV, I set the switchbox, and flip through VCR channels. If I want to play a game, I choose the system using the switchbox, and set the VCR channel to match that of the particular game system (Ch 3 or 4). This setup eliminates the daisy-chaining of multiple system RF switches, which will degrade signals. The primary VCR also has gain control circuitry, which boosts the game picture a little.

The composite stuff (DVD, 2nd VCR, Dreamcast, PS2) is piped into a composite switchbox. The output of the composite switch is then connected to the AUX input on teh primary VCR. So, if I want to use something that runs composite, I set the VCR channel to AUX, and select the device via the composite switchbox.

I know the above is rather inelegant, but it works, and with the A/V equipment I own, it is the best solution at this time.

Hope this helps.

Yeah, I can use the "piggyback" method, and I have before, but what I want is to be able to do is to switch them with a knob. These are going to be integrated into my MAME cabinet and I would like to connect an external switch, like I can with other consoles. But, maybe the piggyback will be easiest.

That would be SO cool to have an Atari 2600 hooked up...i have mine, but its in the closet at the moment.

Mad Catz is releasing an RF system selector in the next couple of weeks. I have held the prototype in my hands.

I remember Nyko had some sort of RF switch box a few years back.

An rf system selector from Mad Catz is what I will wait for then. Thanks.

You don't have to wait for the MADCATZ system selector...
You can go to your neighborhood Rat (radio) Shack and get an RF(Coaxial) Switchbox. That's what I use. From what I remember, it wasn't that expensive either. They have two and three switch models, and they might have a 4 switch in the catalog, but I didn't look.