Marcs aerial is Group K which will be down on signal compared with the proper group B. 4G or 5G filtered is marketing hype. 4G is much higher than TV frequencies and unlikely to cause any problem unless the mast is 30 yards away. 5G could be a problem if there was a mast nearby (which kezo confirms there isn’t) and a decent lowpass filter inline would deal with it.
From my understanding from the manufacturers blurb Marc has a Wideband Group T aerial covering channels 21-60, therefore 4g would interfere with the aerial. The manufacturer states its filtered for 4g, which is more than likely done by the way the coil is winded rather than actual filter. Yes he could fit a decent 5g filter which is no different to a lowpass filter.
Correct why a group B aerial is 4g and 5g filtered I don’t know but some of the quality brands you won’t get from the likes of screwfix wind the coils to filter these out!
Since the 700mhz clearance in 202o there aren’t any channels over ch48 674-680MHz, bringing group K as the new wideband aerial Ch21-48 (470-686MHz)
From 2013-2022 the group T was classed as the widedband aerial use to go from ch21-60 470-790Mhz)
Prior to that group W was the wideband going to ch68 (seems like yesterday)
The pint of a dedicated grop aerial in this case a group B would focus on the channels Marc recieves rather than focus on all the groups.