When you say coax do you mean composite video without audio or RF?
You can't carry composite video and audio over a single coax cable but you could do just video.
The Miracast stick can be powered from any USB power supply.
You could convert the HDMI output to composite video and audio. Then split the video to connect both TVs
If you want audio too you would have to convert the av connection to RF with a modulator.
It's easier to split the signal after it is converted from HDMI to video or RF.
I am not sure, this seems complicated. Are there devices that split the video from the HDMI device and the audio? It seems I would need multiple devices and I cannot afford the room. I would need a device that connects the Miracast HDMI device to multiple coaxial outputs, then an RCA or 3.5 mm connection. From the splitting device, I would then run both the coax for video and the audio wire to the televisions were I would hook them up?
I can purchase HDMI splitters single inputs multiple outputs, I assume these carry audio and video. I am trying to use the Miracast in a device like that. Miracast to HDMI connection and USB power, split to multiple coaxial(not 3RCA but the standard run of the mill coaxial RG6)outputs, wired to the televisions.
This is all new to me, thanks for the input. Sam