Hi - My TV picture intermittently breaks-up for maybe 30 seconds every half an hour or so. I want to fix it and so have starting trying to diagnose the root-cause.
I've read that a Freeview digital signal should be no higher than 75dBuV? My TV shows a Signal Strength of 91dBuV - could this be the problem?
I'm using BT Vision. I have a masthead amplifier which is powered by a booster next to the TV. If I unplug the booster, then I get no signal at all. I didn't install the amplifier or the booster - they were here when I moved in.
Would appreciate any tips.
Many thanks.
Analogue needed about 75dBµV at the aerial socket. Digital needs less.
Signal power level depends where it is being measure from. The simplest method when you're troubleshooting as you are is to go from the back of the set. You're looking for a minimum of 45dBµV and a comfortable target level of 55-60dBµV. Most sets will accept something a little higher but going OTT will cause problems. 70dBµV is about the most you want to have at the aerial socket on the TV. Signal
quality is more important than signal level.
If you have decent quality coax cable (WF100) then your signal loss over distance will be around 0.15dBµV/m. Average installs use between 20 and 30metres of cable from aerial to the main lounge TV. So if we add that back on to the signal level your TV is reporting then the mast amp is generating somewhere between 94 and 95.5dBµV. The gains from the loft amp/spitter will be offset by some losses due to the connections.
We are presuming that the TV measures signal level reasonably accurately. But even if it overstates by 10%, you've still got about 82~83dBµV at the set when you really only need 60dBµV.
If the system has been installed a while then it could predate the Digital Switchover. After DSO when analogue was no longer transmitted then the power of the digital transmissions was bumped up. Your system might have been installed and set up for digital when it was on low power. Now the power level has gone up then the level at the TV is a bit OTT.
Do you have access to the loft? If so it's also worth checking the wiring on the Labgear distribution amp. There are models in the range that include a "Full" output. This is designed for connecting to a second distribution amplifier. If it's connected to a TV then the signal level going down the wire is the full beans; 99dBµV. If yours is wired using the Full output then switch the cable over to one of the numbered outputs instead.
Once you've checked all this then get yourself some attenuators. There's a range of fixed and variable ones here on the
Satcure page
