UKColchester
England · DAB
- Position
- 51.917186, 0.925799
- Grid reference
- TM01312834
- Nation
- England
- Ground height
- 45 m
- Antenna height
- —
How far it reaches
Two different questions, and the map below can be switched between them. Reaches is everywhere this mast puts a usable signal; strongest is the much smaller slice where nothing else does it better.
| Band | Reaches | Strongest in | |
|---|---|---|---|
| DAB radio | 0.5% of UK Output Areas | under 0.1% of UK Output Areas | a relay, serving a local area |
More detail
Most places can receive several transmitters — a median Output Area hears twelve — and only one of them can be the best, which is why the two columns are so far apart. Reach counts an area once the model clears the reception threshold there at all, and it inherits the sweep's screen: only the strongest twenty candidates per area are stored, so a mast lying twenty-first somewhere does not count as reaching it. Both are a share of areas, deliberately, and not a number of homes: checked against Ofcom's own coverage the model ranks transmitters correctly (Spearman 0.861) but over-states how far each one gets by a median factor of 2.5. A share is a ranking statement and survives that; a household count would not. How this is worked out.
On the map
Everywhere Colchester is predicted to reach for DAB radio, shaded by how much signal is left over. Other transmitters reach most of this ground too.
Only the areas where Colchester is the strongest option for DAB radio — the ones the postcode lookup would send here. A smaller picture than its reach, and a different question.
The lines are how far the signal is modelled to get: solid while the margin still clears 10 dB, dashed out to where it last clears 0 dB. The real edge sits inside them — every point inherits the model's measured optimism of about 17 dB.
How the rings were drawn
It is an envelope, not a boundary: terrain can still block reception well inside it, and it is an edge, not a fill — the colour says how far the signal gets, not that every spot under it works. Zoom in and the shading gives way to the per-area prediction, which is the same question answered Output Area by Output Area. The DAB radio ring was contoured from the stored predictions, which keep only the strongest candidates for each area — the true edge can extend beyond what is drawn [I].
The modelled outer edge drawn above: DAB radio about 40 km toward the south but only 9 km toward the east [I].
Open this transmitter on the full mapreach, the aerial direction, and everything else within range
DAB radio
| Ensemble | Block | Frequency | ERP | Height | Area | EId | Services |
|---|---|---|---|---|---|---|---|
| SDL National | 11A | 216.928 MHz | 1.0 kW | 39 m | Colchester | C1CE | 31 |
| D1 National | 11D | 222.064 MHz | 444 W | 39 m | Colchester | C181 | 30 |
| Essex | 12D | 229.072 MHz | 500 W | 39 m | Southend and Chelmsford | C19C | 13 |
SDL National — block 11A
D1 National — block 11D
Essex — block 12D
SDL National — radiation pattern
Radiates most strongly toward the south-west (230°), as published by Ofcom.
More detail
Each ring is 10 dB of attenuation below the pattern's own peak; the outer rim is the peak itself and anything 30 dB down or deeper is drawn at the centre rather than off the edge of the chart, so a very deep null reads as “weak” and not as a hole in the picture. The shape says which direction radiates harder relative to the mast's own peak, not the absolute field strength there or how far it reaches — that is what the coverage map and the postcode lookup are for.
D1 National — radiation pattern
Radiates most strongly toward the south-west (230°), as published by Ofcom.
More detail
Each ring is 10 dB of attenuation below the pattern's own peak; the outer rim is the peak itself and anything 30 dB down or deeper is drawn at the centre rather than off the edge of the chart, so a very deep null reads as “weak” and not as a hole in the picture. The shape says which direction radiates harder relative to the mast's own peak, not the absolute field strength there or how far it reaches — that is what the coverage map and the postcode lookup are for.
Essex — radiation pattern
Radiates most strongly toward the south-west (230°), as published by Ofcom.
More detail
Each ring is 10 dB of attenuation below the pattern's own peak; the outer rim is the peak itself and anything 30 dB down or deeper is drawn at the centre rather than off the edge of the chart, so a very deep null reads as “weak” and not as a hole in the picture. The shape says which direction radiates harder relative to the mast's own peak, not the absolute field strength there or how far it reaches — that is what the coverage map and the postcode lookup are for.
Other transmitters nearby
Every structure Ofcom list within 40 km, nearest first. Close is not the same as an alternative: most of these are single-service relays, and one of them may radiate a thousandth of this mast's power in a direction that misses you.