Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Either defective or doesn't work as advertised

I bought three of these. I tried two and both blocked my DISH network signal completely and made no difference, or slightly degraded, the over the air signal. I either happened to open the two defective ones (didn't bother trying the third), or these just don't work for DISH or as advertised for over the air. I have returned all three.