# UK Amateur Radio ## Foundation Licence 2002
### Feeders & Antennas Part A
The words antenna and aerial have the same meaning and are interchangeable.
Feeder requirements The cable leading from the transceiver must be capable of carrying the signal to the aerial with as little loss of power as possible and without radiating any signal. To this end a cable called Coaxial Cable can be used. The construction of such cable is a centre core down which the signal is passed of either a solid copper wire or several thinner copper wires. This centre wire is covered by a layer of insulation called the dielectric and that in turn is cover with a brading of wire called the screen. Finally the whole lot is covered in a protective plastic layer to prevent damage and resist water getting inside.
The coaxial cable is by far the most popular feeder cable in my shack but other forms of feeder do exist as shown below.
Above are shown two types of ribbon twin feeder where the two outer wires are covered in a protective layer apart by a plastic strip which is all part of the protective layer but it has been slotted. The left hand one was a cable about 12mm overall width where as the right hand one is about 25mm overall.
Open wire feeder which is a parallel pair of wires held about 100 mm apart by plastic formers which have insulated ties to hold the wires to the formers.
The connection from the cable to the transceiver is achieved by using, according the the frequency of operation a BNC connector or a PL259 connector.
Above is shown the BNC connector. You will need to be able to identify this connector and know that it is used particularly on equipment operating at UHF, that is 433MHz and above. This connector is a bit like a normal bayonet light bulb in that it pushes onto the connector and with a twist locks into position just like a light bulb pushes into its connector. | The picture above is the PL259 connector and is used on equipment from the low HF bands 1.8mhz to the VHF band 144MHz. This is a screw connector. The outer casing engages onto the connector on the transceiver and then several turns are necessary before it is tightened up. It should be fully tightened.
The construction of both connectors is similar in the respect that each connects the braiding to the outer casing and the centre to a central pin. In the case of the BNC the braiding is held in place by a friction connection caused by tightening down a water tight nut. On some PL259 connectors the braiding may need to be soldered to the outer casing. When making up the connection onto the cable it is necessary to check that there is a connection between the braid and the outer and between the centre and the feed wire in the centre of the cable. There must not be a short between the outer braid and the inner wire else the cable will not operate correct and damage to the transceiver is possible. Use a continuity tester to check this.
The photo above shows what is called and EGG INSULATOR, so called because of its shape. A one pound coin is at the side to give you some idea as to its size. This is but one of many different types of insulator that could be used at the end of a dipole.
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