I am just now setting this unit up to record OTA shows.
A good quality TV antenna is routed into the HW130STB and out to my TV, and I get perfect reception on the TV for all channels.
When I set my TV to channel 3, turn on the HW130STB (using that as a tuner) and set it to 12-2, the image is pixilated.
The signal gets from the HW130STB out the 3 RCA cords, which go through an A/B switch, then into an HDMI converter, from there to my second HDMI input on my TV.
Have only taken a brief look at other channels when tuned through the HW130STB and those looked okay.
I have the HW130STB as well as a Tablo and there are really few similarities. I would suggest you do a Google search for that model number and I think you will find a number of sites that have information. There are several variations of the device that I suspect are very similar so I think you will probably find your answer there. Good luck!
You might want to try reddit or something. Pixelation usually is from poor reception which implies (likely) that somewhere you’re getting some signal loss in your setup.