RF to HDMI conversion?

Some AVR's will upscale and convert analog inputs, composite and component, to an HDMI output. Check your AVR, you may already have that capability.

If the Colecovision really has RF output (screw-on coaxial cable and not the push-on RCA plug for composite video which is usually color-coded yellow), the signal is probably like an NTSC channel 3 or 4 signal from an antenna or VCR. It was intended to be connected to a TV that has only an antenna input. There are cheap RF demodulators that were intended to connect such devices to a composite-video input (yellow RCA jack), but I've never seen one with an HDMI output.

If your projector has a composite-video input, I'd get one of those RF demodulators.

If you have only an HDMI input, you need an NTSC/ATSC tuner that has an HDMI output and can convert an analog NTSC broadcast signal to digital for the HDMI output. I actually have such a device; it's a Sony HD DVR that cost several hundred dollars, seven years ago.

An RF to video converter is a receiver. It would seem that you need an HDTV receiver with HDMI out. The Samsung DTB-H260F is an example that should be available on ebay. There are other similar units available if you look around.

The Samsung DTB-H260F doesn't receive analog RF (NTSC) signals. (I've used one, BTW.) Very few standalone HDTV tuners have been able to receive NTSC signals.

According to http://www.avsforum.com/t/179095/the-official-avs-hdtv-stb-synopsis the only currently-available non-DVR HDTV tuner that can receive NTSC is the PrimeDTV PHD-8VX.

http://www.epvision.com/HDTVSTB/phd8vxmain.htm
http://www.avsforum.com/avs-vb/showthread.php?t=1205954

What you need is an RF Demodulator. Got an old VCR laying around? That should work. Connect the Coleco to the antenna input on the VCR and the video and audio outputs to the projector. The yellow should be the video input.

If your Coleco has only a single RCA connector video output then it is outputting SD video only and there is not need to connect it to a HD HDMI input. Just run a single RCA connector cable from the Coleco output to the Yellow NTSC video input connection on your projector.

...or, you could read the thread and see that he has an RF output.

The RF demodulator will also have red and white RCA jacks for stereo audio, so you would connect those to the projector for sound. Three RCA-type cables in all.

It's been at least 12 years since I bought an RF demodulator, but they used to be available at places like Wal-Mart and Radio Shack for maybe $15.