Point it at the transmitter that serves you, matched to its polarisation, along a path clear of hills.
Six practical steps, from finding your transmitter to the final retune. Each one shows how to do it with Tower Aim, our app, using Ofcom's transmitter data.
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Read this, then follow the steps below for the detail.
Point the aerial at the TV transmitter that serves your area, which may be a main station or a smaller relay, with its elements matching that transmitter's polarisation: flat for horizontal, upright for vertical. Check that no hill blocks the path, then fine-tune and retune every TV.
Systemic Studios makes Tower Aim, the app this guide uses for each step. Roof work is dangerous: if your aerial is hard to reach, use a professional aerial installer.
Do steps 1 to 3 on the ground, before you get the ladder out.
Your aerial should face the transmitter that serves your area, which is not always the closest one. Tower Aim recommends a transmitter based on published power and distance, not a signal measurement, from Ofcom data covering every digital TV transmitter in its list: 3,830 multiplexes across 1,041 sites, dated 8 October 2024. Search by postcode or town, or use your location.
Transmitters send either horizontally or vertically polarised signals, and the aerial has to match. Horizontal means the elements lie flat; vertical means they stand upright. Main stations are often horizontal and many relays are vertical, so check before you climb. Tower Aim shows the polarisation for each transmitter, with its multiplexes, UHF channels, frequencies and power.
A hill between you and the transmitter can block the signal. Tower Aim shows the elevation profile along the path, which works from a one-time terrain download, and Tower Aim Installer adds finer terrain. Trees and buildings are not included, so treat it as a guide. If the path is blocked, a relay may serve you better.
Stand at the aerial, or directly below it, and face the bearing to the transmitter. Tower Aim's live compass arrow shows which way to turn and confirms when you're aimed in the right direction. With AR aiming on supported phones, you can see the transmitter's direction through the camera.
Loosen the mount just enough to turn the aerial, then move it in small steps while someone watches the signal quality screen on the TV. Tighten it, then run a full retune on every TV and set-top box. If one multiplex is missing and the others are there, recheck the aim, then retune again.
Many areas, often in valleys, coastal towns or behind hills, are served by a smaller relay rather than the main station. Relays often carry fewer multiplexes, so a main station further away can give you more channels if the path is clear. Tower Aim lists relays alongside main stations, with the terrain to each and what's worked for neighbours nearby, once enough reports are in.
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What to check at each step, and where to find it in the app.
| Step | What to check | In Tower Aim |
|---|---|---|
| 1. Find your transmitter | Which transmitter serves you | A recommended transmitter based on published power and distance, not a signal measurement, with estimated reception; Ofcom data dated 8 Oct 2024 |
| 2. Polarisation | Horizontal or vertical | Shown for each transmitter, with its multiplexes, UHF channels, frequencies and power |
| 3. Terrain | Hills between you and the transmitter | Elevation profile from a one-time terrain download; finer terrain with Installer |
| 4. Aim | The bearing to the transmitter | Live compass arrow that confirms when you're aimed in the right direction; AR aiming on supported phones |
| 5. Fine-tune and retune | Signal quality on the TV, then a retune | UHF channel numbers and frequencies for each multiplex |
| 6. Relays | Whether a relay serves you better | Main stations and relays from Ofcom's list on the map, with the terrain to each; what's worked for neighbours nearby, once enough reports are in |
| On the roof | What's saved on your phone | Transmitter data built in; one-time terrain download |
Real Tower Aim screens at a London address.
See nearby transmitters on the map, then their multiplexes, channels, power and polarisation.
Look at the elevation profile to the transmitter before you climb.
Follow the compass arrow, or AR aim on supported phones, while you turn the aerial, then check reception on your TV.
Small habits that make the job quicker and safer.
Only work on a roof if you can do it safely, never alone and never in wind or rain. If the aerial is high or hard to reach, use a professional aerial installer.
Look up the transmitter, bearing, polarisation and terrain in Tower Aim before you climb, so the time on the roof is just aiming.
If the arrow seems off, move the phone in a figure-eight to calibrate it, and keep it away from metal and magnets, including magnetic phone cases.
Aerials nearby usually point at the same transmitter. If yours faces a different way, or its elements are the other way up, find out why before you change it.
TV signal readouts lag a little. Turn a few degrees at a time and pause before you judge the picture.
Some UHF channels that used to carry TV are now used by 4G and 5G. If the picture breaks up near a mast, especially with an amplifier, a 4G/5G filter can help.
Tower Aim: TV Aerial Finder
We make it. These are the parts that match the steps above.
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Ofcom data dated 8 Oct 2024: 3,830 multiplexes across 1,041 sites, main stations and relays, with channels, frequencies and power. The recommended transmitter is based on published power and distance, not a signal measurement.
Horizontal or vertical for each transmitter, and the multiplexes it carries, shown before you aim.
A terrain line of sight from a one-time terrain download, with finer terrain in Tower Aim Installer.
A live compass arrow that confirms when you're aimed in the right direction, plus AR aiming on supported phones. Then check reception on your TV.
See what's worked for neighbours nearby, once enough reports are in.
Aerial installers, electricians and AV professionals can add Tower Aim Installer, an optional subscription, for jobs, readings from your own meter, photos and branded PDF reports.
Confirm the transmitter, record the job and hand over a report on site.
Jobs, readings, photos and PDF reports, step by step.
Features, screenshots, Tower Aim Installer and support.
At the transmitter that serves your area, with the elements matching that transmitter's polarisation. Tower Aim recommends a transmitter based on published power and distance, not a signal measurement, and shows the bearing, polarisation and terrain to it.
Match the transmitter you are aiming at. Tower Aim shows horizontal or vertical for each transmitter. On a horizontal aerial the elements lie flat; on a vertical one they stand upright.
Not always. A main station further away, or one with a clear path over the hills, can serve you better than a small relay nearby, and relays often carry fewer multiplexes. Tower Aim recommends a transmitter based on published power and distance, so check the terrain to each option too.
A smaller transmitter that rebroadcasts the main station's multiplexes into an area it does not reach well, such as a valley or a town behind a hill. If you are in a relay's area, point at the relay and match its polarisation.
From Ofcom's Digital television transmitter details, dated 8 October 2024, the latest edition Ofcom publishes. It covers 3,830 multiplexes across 1,041 sites, main stations and relays, in England, Scotland, Wales, Northern Ireland, the Isle of Man and the Channel Islands.
Yes. Over-the-air digital TV, including the Freeview channels, comes from these transmitters, so aiming at the right one with the right polarisation is the first step. After aiming, retune every TV and set-top box.
Yes, for direction. Tower Aim uses your location and your phone's compass to show the bearing to the transmitter and confirm when you're aimed in the right direction, with AR aiming on supported phones. A phone cannot measure TV signal, so finish by checking reception on the TV.
Yes. Run a full retune on each TV or set-top box after aiming. If one multiplex is missing and the others are there, recheck the aim, then retune again.
Check the polarisation, the terrain between you and the transmitter, and the cables and connections. Trees and buildings can also block the path. If you are near a mobile mast, a 4G/5G filter can help. If the main station is blocked, a nearby relay may be a better target.
The transmitter data is built into the app, and the terrain map is a one-time download that stays on your phone. Open the app once on Wi-Fi before you head up.
No. Your phone cannot measure TV signal. Tower Aim recommends a transmitter based on published power and distance, and shows "Estimated reception" from Excellent to Poor. It is an estimate, not a measurement. Installers can record readings from their own meter with Tower Aim Installer.
iPhone with iOS 17 or later, and Android 8.0 or later, for outdoor, loft and rooftop UHF TV aerials.
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Systemic Studios