The one I bought is about as much use as a chocolate fire guard, it sits in a drawer at home these days. My van has a omnidirectional aerial fitted that with the old analogue signal was useless. Now with a purely digital signal it works well. In the places where the signal is weak it will still find a signal if one is there so I Use this to tune the TV then find the strongest channel and go outside with my directional aerial and use the signal strength indicator on the TV to align the aerial to its best position. Now when you retune the TV everything tunes in well.
------------- Bill
For a licence dated 1997 or later you must add together the plated max weight of the caravan and trailer, if the total is 3500 or less you can tow it. You may even tow a caravan with a MAM greater than the cars unladen mass the restriction was removed in 2013
I look for direction of others on site turn TV on and select set up menu and shows signal strength turn aerial for highest reading so no need for any other device
If you have a smartphone get the Antenna Aligner app. It uses your smartphones GPS and its database to calculate the nearest transmitters to you. Its available for Android and iPhone.
You choose from the list of available ones at your location and it shows a compass with a big needle saying 'point antenna this way' simples*