Your ability of receive all the Freeview transmissions depends on the suitability of aerial
the design style,
the "group", and
its physical location.
Standard type - Yagi aerial
The standard type of TV aerial is known as the Yagi aerial. It is mounted on a pole, and consists of a rod with a reflector (shown green) at the back and many spiky elements (in grey) at the front. The connecting cable connects to the element nearest the reflector, known as the driver (shown in blue).
These Yagi aerials are directional and so pick up signals best from a transmitter that the rod points towards. The more elements the aerial has, the better it picks up a signal and becomes more directional.
A standard-type aerial is all that is required for digital TV reception in most places. These antennae have between 10 and 18 elements and a single reflector. These are recommended for new installations for good digital television reception, but will more often than not function perfectly in good reception areas.
Typically these aerials are designed to receive only some transmission frequencies - see "groups" below.
High Gain aerials
These aerials are designed for poor digital reception areas, and have two reflectors. For maximum signal strength, some digital high gain aerials have up to 100 elements. Since the switchover to digital-only transmissions back in October 2012, most UK households now have good quality digital TV signals.
A more expensive aerial is only required where the signal strength is low, but can often provide the whole Freeview reception where it might otherwise be impossible.
The CAI (that represents aerial installers) has four standards for digital TV aerials. The highest standard "1" is for homes on the fringes of coverage areas, intermediate standard "2" is suitable for use within the coverage area; minimum standard "3" is for good coverage conditions.
These aerials can be either wideband, or receive only selected frequencies - see "groups" below.
You may haved used a 'Grid aerial' for analogue reception, but as they are generally unsuitable for Freeview reception, they have now generally been replaced by the Yagi type. However in some places a Grid aerial installation may work for Freeview: otherwise replace with a standard Yagi aerial.
Indoor aerials are generally not suitable for Freeview reception. In areas of good signal strength it is often possible to receive some transmissions. Even where an aerial works, people often find that may get interruptions to their viewing (or recording).
Loft mounted arrivals are not generally recommended for Freeview reception, as the roof tiles and plumbing will degrade the signal. Some compensation for this loss of signal can be made by using satellite-grade cable to connect the set top box to the aerial.
The best position for a TV aerial is mounted outdoors, as high from the ground as possible, pointing directly at the transmitter. The signal can be blocked by hills and tall buildings. It should be positioned away from any other aerials.
Horizontal or vertical?
The transmitter will either use vertical mode which requires the elements of your aerial to be up-down, or horizontal mode which requires them to be level with the ground.
Both analogue and digital television is transmitted the same group of transmission frequencies (known as channel 21 through to 60). A coloured marking on the aerial shows the group.
To create the best possible analogue picture, TV transmissions from adjacent transmitters have been designated to several different groups of frequencies. By using an aerial that receives only the channels in the correct group, the analogue picture can be kept free from interference.
To receive Freeview transmissions from the same transmitter it has been sometimes necessary to use frequencies that are not part of the transmitter's normal group. When this has occurred, the aerial will need to be replaced with a "wideband" aerial (also known as group W) - one that covers every group.
As Ofcom is planning to move the TV frequencies again - perhaps as soon as 2018 - it may be wise to use a wideband aerial if you can to ensure you can keep viewing Freeview for many years to come.
Depending on exactly where in Portsmouth you live, I suspect your likely transmitter is Rowridge, on the Isle of Wight. If you look at https://ukfree.tv/transmi…dge, you will see that it covers most of Portsmouth and the surrounding areas. You will note that some multiplexes are transmitted with horizontal polarisation and some with vertical and some with both. It would appear that you will need a Group A aerial set for vertical reception and another set for horizontal reception if you want to receive all the services as LSO, COM7 and COM8 are horizontal only, the rest being both vertical and horizontal.
Do not fall for the scam of a 'digital' aerial as there is no such thing, *all* UHF aerials are able to receive television transmissions irrespective of how the picture and sound information is encoded onto the carrier signal. But aerials are banded, depending on the frequency range you want to receive. For Rowridge most of the signals fall within the Group A band, the exception being COM8 that is right at the top end of the band. The link stated earlier shows the channels and frequencies for all the services and which programmes are on what multiplex.
Hope that helps? If you need any further guidance, please give a full post code, or that of a very nearby shop or post office, so we can identify the reception conditions at your locality.
Toby: Hi, Toby. If you are thinking of replacing your old aerials with a new one, you need what we call a 'grouped' aerial. Your recommended transmitter is the Full Freeview main transmitter at Rowridge Farm on the Isle of Wight, for which you require a group 'A' aerial. Now, some of the CHANNEL groups, known as multiplexes are transmitted with vertical polarisation, so you may wish to experiment with your new aerial elements (the little rods that go across the arm of the aerial) arranged vertically instead of horizontally. The main channels, watched by most viewers are transmitted with equal powers at horizontal and vertical polarisation. It's up to you to try and find out which is best, depending upon the channels you wish to watch. It would be a good idea to replace the old aerial cable with new as well. You should choose the type of cable that has a silver foil wrap around a copper braid around a polythene insulator around a strand of thicker copper 'inner' conductor. Replace the coax aerial plugs and sockets with new ones too. It might be worth your considering mounting your new aerial on the roof or chimney instead of putting it in the loft, but you could try the loft first and see how you get on. Post again if you run into any problems. Richard, Norwich.
Toby: rather than worry about the aerials, which at least get you something, think about the wiring from them. It could be that the aerials are the opposite of what is required, but as Richard advised, think about the wiring. Everything degrades, and wiring, connections, etc fray, get corroded, etc. A dodgy wire can let through one mux (say BBC), but not any others.
If everything is inside, try replacing the wiring - screwfix or toolstation - something like this :http://www.screwfix.com/p/labgear-rg6-satellite-coaxial-cable-50m-black/72537 (I know its Labgear, but still...) would do, and all you need to do is attach the connections to each end (which they also sell).
ATV SheffieldSatellite, Television, FM, DAB, Aerial, Coaxial Cable, Plugs, Sockets, Connectors & Leads will also sell you stuff (and yes, its probably better than the Labgear stuff), and will show you how to attach the end bits (always fiddly). Or get a pro to refit the whole lot.
Many of us who contribute to this website do mention log-periodic aerials when it is appropriate. They provide a degree of 'future proofing' as well as excellent performance. I use a log36 myself and have been extremely pleased with its performance, hence I recommend then where appropriate.