Making the most of your receiver Eddystone Stratton VK7AG 0003
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For general all round reception of the whole range of frequencies covered by the receiver, an aerial about 60 feet long is recommended. The greater portion of it should be well out in the clear and as high above the ground as can con- veniently be arranged. A tree is often available and can well be used, but the aerial proper must not be allowed to touch the leaves or. branches—an insulator well out from the tree will ensure this (see Fig. 1). Also. keep the aerial well away from metal roofs, gutters, etc., even if this means shortening it to some extent. Signal pick-up is greater when the aerial is kept away Fig. |. A good general purpose aerial. It should be kept from anything clear of all obstructions. likely to act as a screen and this point is definitely more important than obtaining maximum length. Good insulation is necessary at the lead-in point. Excellent results will be obtainable on aerials much shorter than 60 feet, par- ticularly on the shorter wavelengths. This applies especially on board ship, where it may be difficult to erect a long aerial. At the rear of the receiver are two terminals, one marked ‘‘A’’ and the other ‘‘AE”. The latter is normally strapped to the chassis and should remain so when a single wire is used. The aerial lead-in wire is attached to terminal ‘“A"” and the earth to terminal ‘‘AE’’. By the way, if you are temporarily stuck for an aerial, try connecting an earth lead to the aerial terminal ‘‘A’’ (leaving “AE” blank, of course). It is surprising how good results can be with this system —often they are better than with a poor indoor aerial. ol SPECIAL AERIALS. Past experience shows that many listeners are particularly interested in certain shortwave broadcast stations, or possibly in one of the amateur bands, and wish to obtain optimum results just where their interests lie. In such cases, the Oe ee dipole (otherwise pees eo a _atm—— known as the doub- let) type of aerial, is recommended. As Ly can be seen from the sketch in Fig. 2, it \ consists of two equal 698 lengths of wire “‘a TWIN FEEDER CABLE. SS g and ‘‘b’’ attached to axe a centre insulator, Ca from which a twin EARTH LINK REMOVED. feeder (or trans- Fig. 2. The dipole or doublet type of aerial. the benefits Mission line) runs to of which are explained in the text. the receiver. This feeder, which takes the form of two wires embedded in solid insulating material, is convenient _ to use and easily obtainable. Alternatively, two 18 gauge wires (bare or enamel- covered) may be employed, small spacing insulators being fixed at intervals to keep the wires separate. The length of feeder, within reason (say up to 100 feet) has but little effect on the performance. 3 The two feeder wires are connected to the aerial wires, one each side of the centre insulator. At the receiver end, the two wires are attached to the “A” and “AE”? terminals, the shorting strap or plug being removed. Two further benefits derive from the use of a doublet aerial. Electrical interference, radiated off the electric mains, is picked up equally on each of the pair of wires and the induced voltages tend to cancel out, so that reception Page Two oi dt . becomes free of insulation (unle come into cont mechanical pro’ tion being rubl Where int wires can be ad of the appropri: V Broadcast Amateur WIDE BAN! If additior reception ové Also, a cross- frequency ran The lengt the additi« wires should be made acco to the fore table. For exa Fig. 3 show aerial with pairs of wir space pe more wires ¢ added. The dra back to t aerial shown Fig. 3 is tt four supporti points are | quired. folded up vy sion of the sa aerial is sket ed in Fig. Only two m supports called for, lower porti of the ae being ancho: FOLDED | An exc _ wave broad: There 2 ribbon feeds out—for th Strain insuk: