I have a passive UHF antenna, with a 1:2 splitter close to it, short run for tv1 is about 5 meters, long run for tv2 is about 15. I have 4 digital channels on my grid, and tv2 does not receive enough signal on one of them. Question is can it be improved with an inline amp(passive)?
Will an inline amp improve your signal? Yes a amplifier will boost the signal that is available. With that said there has to be enough signal to amplify. In the past I have found many DIY connections that were not made with the correct type of coax or connectors. Each connection has some power loss measured in DB mis matching the impedance of an antenna to the type of coax can reduce the signal to a level that can not be recovered. A matching network may be needed from the antenna to the coax to reduce the losses. The amplifier should be prior to the splitter and the splitter should be the type for the frequency range (UHF) you are targeting. The last item to watch is splices each splice has some power loss. 3db of loss cuts the power in 1/2. Remember that a splitter will reduce the signal. More expensive splitters usually have a lower loss (check the splitter it may be a 60/40 or 70/30 not 50/50 as you would expect these are very inexpensive to build and you may be able to flip the splitter and both tv's might work). There are amplifiers that have multiple outlets and will run on a 9V battery for over a year but these devices are harder to find now since the demand has decreased over the last 10 years. One last note getting the highest gain amp is not always the best deal a 15db amp with a low noise may do better than a 30+ db amp with a higher noise level.