Llangynog
Wales · TV
Position 52.823057, -3.409776 Grid reference SJ05102599 Nation Wales Ground height 188 m Antenna height 18 m Aerial group Group A — C21–37, the low end of the band Polarisation Vertical BBC region Wales ITV region Wales ITV news region Wales Parent transmitter Long Mountain Ofcom site number 13536 The position is our conversion of Ofcom's grid reference SJ05102599 from OSGB36 to WGS84 [V] . Ofcom publish no latitude and longitude for television sites. The transform is verified rather than assumed: on the 3,403 radio records that carry both, it reproduces Ofcom's own coordinates to within 0.1 m. OpenStreetMap has a mast 1 m away, matched on a name match [V] . That is an independent check on the position, not a correction to it — see how positions were checked .
On the map
Llangynog is not the strongest signal anywhere the model predicts — it is shown here in place. That is normal for a relay, which fills in inside a main station's area.
Television This site carries the three public-service multiplexes and none of the three commercial ones, which is the normal arrangement at a relay — 1,059 of 1,169 sites are like this. Channels on SDN, ARQ A and ARQ B are simply not transmitted here, and no aerial will recover them; they need a main station. PSB3 (BBC B) is the UK's only DVB-T2 multiplex and carries every HD channel. Losing the HD channels while keeping the rest is therefore a single-multiplex fault rather than an aerial problem.
Transmitter data is Ofcom's; every dataset and the terms it is used under are listed under sources . Coverage figures are modelled, not measured, and are systematically optimistic .