Are you able to get reception using that TV point with another TV to rule out an aerial faiulre.
Secondly what is the make and model of the TV?
What is the signal strength for the HD channels normally (when not at 10%), secondly is this a new fault or something which has just recently started?
You may find that the antenna cable or aerial is starting to degrade, which is causing signal loss. For SD channels there is sufficient error correction but with HD there is less tolerance, and due to 'digital' you dont really get the option to see a pixelated image like you would with the old analogue signals.
Is your TV aerial external?
I would start by looking at your aerial, see if you can induce the fault as it may be a lose wire.
If you remove the booster\amp what is the signal strength?
The fact its occurring on two tuners rules out a local hardware fault to the TV.
I would be inclined to also buy a high gain cable between the wall socket and the TV just to rule out any local RF interference.
I would be inclined to leave it without the booster and see if the fault is more or less frequent.
Let me know how it goes over the next couple of hours
The only other things I can suggest is look at the cable run, keep the antenna cable from any other wires, as it may be picking up interference.
Secondly look to buy a premium aerial cable, which goes between the wall socket and the TV, you can often pick these up for about £5 off ebay, the retail price is around £10.
Failing that its then a case of replacing the outside aerial, for a high gain one, and potentially replacing the cable which goes between the aerial and the wall socket.
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