I bought a Tablo to extend my antenna channels to other TV’s via Roku and Android Fire TV. I have an external antenna that I’ve been using for several years with no issues. When I connect the Tablo several channels that are just fine when I just connect the antenna to my TV pixelate badly or lose signal completely with the Tablo. I move the coax back directly to the TV and everything is fine. Can’t understand what the difference would be - is the tuner in the Tablo not as good as the one built into the TV (a Samsung)?
One thing that could affect reception is the signal is split two or four ways, depending on your Tablo model.
Your TV is a single tuner.
Is there a power amplifier attached to your antenna coax?
I have a 4 tuner Tablo attached to a Winegard outdoor antenna with an inline amplifier attached before the line goes into the Tablo. ZERO reception issues. I get about 62 channels in my area and the Tablo setup shows 5 Green dots on all.
What does the Tablo say in the setup page about reception levels? If all green, the maybe you have a WiFi issue.
Use TV Fool to locate the proper direction to point your antenna: https://www.tvfool.com/?option=com_wrapper&Itemid=29
Digital signal such as OTA suffers from the cliff effect. The Tablo has an internal 1x4 splitter which results in very minor signal degradation. This signal loss is enough for you to drop off the cliff and receive no picture or pixelation. See the link below for explanation.
Solution: improve your signal with a better / bigger antenna, or better point your antenna towards the broadcast tower for said channel.
Very helpful / informative blog post about this issue:
https://community.tablotv.com/t/having-trouble-tuning-channel-read-this-blog/