Britain is due for an analogue radio switch-off in the next few years, but if and when the national stations go exclusively to Digital Audio Broadcasting, or DAB, local FM transmissions will continue. For people who have already invested in FM tuners, there should be plenty of mileage left in their equipment yet, and it is not too late to think about ways of improving reception.
For the present, there are still issues to be resolved with DAB. Where signal strength is high and the broadcaster allocates sufficient bandwidth, the technology undoubtedly gives superior performance. At present, however, such optimal coverage is not universal, and there are many parts of the country where FM remains a better option. While the call is more marginal in relation to the radio service cable TV providers offer, FM often delivers a better, cleaner sound.
There are several ways of getting improved reception, depending on the starting point. Even households that already possess an outdoor aerial can still add enhancements to improve their signal. For people who are starting from scratch, we evaluate the strengths and weaknesses of the main alternatives, indoor and outdoor. For people who are upgrading, the details about ensuring the best connections can make an important contribution to optimisation process.
Getting Information About Radio Reception
A preliminary step when considering ways of optimising radio reception is to gather information about nearby transmitters. Broadly speaking, good FM reception requires two things: First, the transmitter should be within 40 miles of the receiver, and second, there needs to be good "line of sight". In other words, the signal needs to be as unimpeded by buildings and underlying terrain as possible.
For people who have a roof or else uncomplicated access to a roof, an outdoor aerial is normally a better choice than an indoor alternative. The only qualification is that close proximity to a transmitter should result in a signal that is strong enough to be picked up by an internal aerial, making the installation of an external one unnecessary.
There are two principal benefits of an outdoor aerial. One is that signal strength is higher; the other is that interference is reduced when compared to an indoor aerial. While it is possible to share a television aerial, they are not designed to receive FM radio, and better results are achieved with a dedicated FM aerial. The same is true for AM wavebands although the issue about proximity to a transmitter is less important. It used to be possible to pick up the long wave New York Schenectady station in the Shetland Islands.
Types of Aerial
There are several types of aerials. Some types are better suited to multi-channel FM reception, while others are better suited to amateur radio applications. The main factor is directionality.
Omnidirectional models are capable of picking up signals from several directions at once. They have the disadvantage that the gain is modest when compared to directional types. In addition, they are vulnerable to interference, tending to pick up multipath echoes from nearby buildings or hills.
Simple Dipole Aerials
A simple dipole is the opposite of an omnidirectional aerial. It consists of two poles with a central mount that separates them. In fact, the old-fashioned indoor television aerial with two "ears" forming a V is a dipole design. Dipole antennae can be multi-element, as in the Yagi design commonly used by amateur radio enthusiasts. They give excellent gain but are correspondingly narrow in the spectrum of bandwidth they can tune to.
Folded Dipole Aerials
For FM radio reception, the most common type of aerial is a folded dipole. On their own, these look a bit like a giant sardine can key, but often, they are combined with director rods and reflectors to boost gain. The folded element is less conspicuous. Since these aerials are highly directional, it is possible to mount them on a rotator so that they can be turned toward one transmitter from another in locations where multiple transmitters are in service.
For people who have loft space available, it is possible to install an aerial in the roof cavity. There are one or two advantages to doing this: It is easier to do than an external installation, and the aerial is out of the weather. Compared to a standard internal aerial, the greater size and power of an external design can be enough to make a difference. Even so, the disadvantages are mostly those that attend any indoor aerial since the roof cuts down the signal by half when dry and still more when wet. Some types of roof insulation can also interfere with the aerial's operation as can general domestic appliances.
In urban and suburban areas, an outdoor aerial is often not practical. Compensating for that, built up areas are usually well provided for in terms of transmitter position and power. Even that may turn out to be a disadvantage because the urban atmosphere is crowded with radio signals of various kinds. As well as competing FM stations, there are electrical signals from household appliances, traffic in nearby roads, and radio signals from public service vehicles. Lastly, indoor aerials usually come in one of two forms.
Half Wave Vertical
The premium choice for an indoor aerial is the half-wave vertical, commonly seen with the "half" written as a fraction. The 1/2 wave vertical design delivers reasonably high gain, certainly better than the basic aerial usually supplied with a new receiver.
The more common choice, partly because it is usually part of the package, is a bidirectional dipole. When this type gives adequate reception, users generally do not see the need to seek alternatives.
In circumstances where the transmitter signal is weak, a signal booster can improve reception up to a point. Usually though, there is a trade-off. Being analogue signals, there is nothing to differentiate the desired signals from all the other radio activity in the atmosphere so the amplifier also may boost unwanted signals alongside the desired one.
It is possible to buy signal boosters that are separate from the antennae. They are usually reasonably priced and often designed to support a range of broadcast technologies, such as digital and analogue television and DAB. Alternatively, there are combined aerial and booster packages, which usually are also designed to be useful for a variety of formats.
There is one aspect of reception optimising that has little to do with aerials, and it involves making the best possible connection between the aerial and the tuner. Faulty connections can be a source of interference, and it is important also to use the right type of cable and connector.
Radio frequency signals are most efficiently conducted by a coaxial cable.. This design, patented in the 1880s, consists of an inner core separated from an outer shield by insulating material, which in turn is coated in an external sheath. The design contains the electromagnetic field between the inner and outer cores and enables the cable to run by metal objects without significant signal loss. Some vendors now recommend high-grade satellite cable, although the benefits may outweigh the cost when digital reception is not an issue.
Aerial Cable Connections
At either end of the cable, there needs to be a terminator.. The ideal terminator is a metal that has both high conductivity properties and high resistance to corrosion. Silver and copper both have the former property, while gold has the latter; unfortunately, there is no perfect solution, but the most common compromise is to use aluminium.
Aerial connectors are usually the Belling Lee type. These are in four parts: cap, claw, case, and pin. The cap goes onto the cable first. Remove about an inch, or two to three centimetres, of outer insulation, and then push the claw back to the end of the outer casing, facing back along the cable length. Fan the outer cable layer over the claw. This probably requires undoing the braiding of the individual strands.
Next, remove the insulation from the inner core, not quite to the same point as the outer insulation. Slide the pin over this wire and up against the claw, and then slide the case over the pin and screw to the cap. This action should have the effect of closing the claw over the outer core. After this step, the previously fanned outer cable strands probably need to be trimmed. Finally, solder the inner core to the pin. This step can be omitted since it is a delicate operation, but the connection is going to be the better for it.
When Reception Cannot be Improved
There are circumstances where there is nothing that can be done to improve reception, and others where the necessary communal consensus is so difficult to achieve that effectively nothing can be done. For example, in a city tenement, if the shared aerial on the roof has become damaged, it can be difficult to persuade everyone to share the cost of a repair because often, they have their own cable installation and no longer need an external aerial. An indoor aerial can work if there is a transmitter nearby, but if there is not any around, then there is virtually no signal for a signal booster to work on.
Far from those urban tenements, in rural, hilly areas, the problems can be equally insurmountable. If the local transmitter happens to be the other side of an intervening hill, then it requires a very high mounting for an aerial, which requires strong tethering to keep it stable in high winds.
Buying Aerials and Boosters on eBay
The majority of aerials sold in eBay's listings are multi-purpose, whether they are for outdoor or indoor installation. This suits many people's lifestyles and needs, but if you think you might need something more specific, it can be worthwhile to consult a specialist dealer. Otherwise, the place to begin looking on eBay is the home page. Many vendors put multiple keywords in their descriptions, so a search for "FM aerial" and "FM antenna" yields substantially similar results.
If you are looking specifically for items either with a built-in signal booster or else a signal booster by itself, the search can be trickier because there are other applications for the term, such as mobile phones and computer networks. A search term like "amplified aerial" can yield satisfactory results. Furthermore, coaxial cable and Belling Lee connectors are simple to find, though the Belling Lee design is used for other applications, so "coaxial connector" gives better results than a search on the type name.
Although the presence of FM radio has been diluted as a medium by the rise of digital broadcasting and Internet radio, it continues to be a popular option and is likely to remain so for several years to come. An investment in optimised reception can be rewarded with many long hours of listening pleasure and a continuing relationship with the community of fellow listeners from local stations in particular.
The main decision to be made is about siting. If it is possible to erect an outdoor aerial, then that is normally the best solution although there are times and occasions when a loft installation can be adequate. An indoor aerial is sometimes a last resort, but sometimes it is all that is needed. Many people may start with the aerial supplied with their tuner and only consider routes to optimisation if the performance of the initial equipment proves inadequate. Whichever route it is to be, remember that eBay's listings can provide the necessary equipment and material for all types of installation.