We live in an area in Sydney Australia with very good TV reception. Only need a cheap internal antenna, on the top of a piece of furniture. Very classy. The signal strength shown by the set top box is 100%, except the 7 channels which were 85~90%.
A few months ago we started getting drop outs and image friezes on any 7 channel when it rained, but signal strength was still showing good. Now Digital 44 TVS always has good reception and always indicates less signal, closer to 60%. So what was going on?
On investigation and looking back at when the problem showed up, I came to realize it started to happen after putting an Ethernet switch and some cables near the same piece of furniture. It didn't rain till days or weeks later, so the correlation wasn't obvious, as the reception hadn't changed at the time of install.
The switch was leaning against the antenna cable going to the set top box. The solution was to move the switch all of 20cm away to behind the furniture and not have the antenna cable run along the Ethernet cables.
Also used some CO CONTACT CLEANER on the telescoping rabbit ears joints, but that wasn't the fix. It has now been perfect for 3 weeks, and we have had some almighty storms that caused no problem at all to reception.
It even though the TV signal strength was high, when the antenna was near the switch, that interfered with the received digital signal, causing the error rate to go above that which was recoverable by the set top box.