There is no difference between an outdoor aerial and a loft aerial – except of course can you fit the size of aerial you want or require in the loft. When buying an aerial for the loft, the obvious temptation is to get the biggest and best you can, is this correct? Not exactly.
Before the work, you need to do a loft signal test. A portable TV, a Freeview set top box if your TV has no in-built DVB-T tuner, or a signal meter will do the job. Feed the aerial with a temporary piece of coaxial cable.
Poor Signal Channels First
Concentrate on improving the signal quality on the weakest digital channel first whilst ensuring that all digital multiplexes have reasonably consistent signal quality.
When aerial alignment is complete, disconnect the portable TV and temporary cable and remove it from the loft. Connect the loft aerial to your main TV using the shortest possible length of cable.
In strong signal areas, use meter to assist in aligning the indoor aerial for least picture noise and ghosting on analogue TV channels. The attenuator will make the TV picture noisy, making it easier to find the best install position for the TV aerial in the attic.
If you don’t want to buy attenuation device one crude but effective way of lowering the received signal to assist in optimizing the aerial is by partly removing the TV plug from the television aerial socket until the picture goes noisy. Then make sure the plug can’t move or completely fall out or move whilst you find the best location for the aerial in the attic with the best signal quality reading.
Freeview Signal Quality
If you have an existing Freeview installation, temporarily place your Freeview receiver in the loft feeding the portable TV and align indoor aerials for the best Freeview signal quality indication on the weakest digital multiplex.
Check the DVB-T / DTT signal quality of all channels is above 50% and if necessary re-align or move the aerial slightly to get all digital TV multiplexes at acceptable signal quality (over 40 – 50%). If one or more digital multiplexes is not receivable try changing your aerial for one with a higher gain and Standard 1 CAI Aerial Benchmark.
Remove the Freeview receiver when aerial installation is complete.
Reception Hot Spots
When carrying out any indoor TV aerial installation, try all areas of the loft as “reception hot spots” can often be found inside a roof which give significantly better reception, just moving the aerial a few feet from side to side or up and down can make a huge difference to TV reception.
Check for Ghosting
When fitting the indoor aerial in your loft, always check for ghosting on all analogue TV channels, if analogue TV is still available in your location. If your area is known for multi-path TV ghosting problems, then try a log periodic aerial which offer the best front to back ratio with minimal side lobes and mount it as high as possible in the attic.
Check all Channels
Since the average loft has lots of reflected signals, it is common for a loft aerial to work well on some channels, but not all. It’s important to check Freeview reception on all Digital Multiplexes for your transmitters as well as all analogue channels. If any channel has a poor signal, carefully re-position the aerial to get the best reception of all channels, accepting a compromise location if necessary.
Loft aerial should be well away from pipes. In addition, never point
loft TV aerials directly through attic water tanks or a very poor signal will result.
Try to install the TV aerial as high as possible in the loft, well away from any 240V power cables and lighting circuits. This is particularly important for Freeview reception, where electrical noise pickup from household appliances and light switches can momentarily freeze the picture.
Effect of Loft Materials
Keep the rods (elements) of the indoor aerial clear of wooden rafters and attic metalwork. If necessary, use nylon string to anchor the aerial in between wooden rafters, pointing it precisely in the correct direction. Nylon garden twine is suitable, but make sure the aerial mounting is secure and cannot move.
Mounting a Loft Aerial
Adjust loft aerials on the weakest TV channel first. Bear in mind that the highest UHF channel number suffers the greatest signal loss through the loft roof tiles and brickwork as it is the highest UHF frequency.
When mounted in its final position in the attic, the end of the aerial (furthest from the coaxial cable feed point) should be tilted up slightly by about 1 degrees from horizontal for best results.