Making the most of your receiver Eddystone Stratton VK7AG 0005
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INSULATING SUPPORT. and some addi- tional mechani- is ee fi cal support will LY ay Pan be required at is the centre. b 6 The second method is to employ 14 -or H 16 gauge wire, oe 4 spaced = apart LIZZ jg- RECEIVER TERMINALS. with small in- Fig. 5(a). Folded dipole aerial, constructed with_300 ohm feeder penionn oo 2 cable throughout. other high grade insulating material. This system is illustrated in Fig. 5(b). The lengths of the arms will be as shown in the table given earlier for the dipole aerial. The folded dipole will give maximum efficiency at the frequency for which it is cut, but it will also give good results on harmonic frequencies. The length should be made to correspond with the band in which the user is mainly interested. For instance, an aerial constructed with arms each 33 feet long will ensure excellent reception on 40 and 20 metres. Results will be good on 10 metres but, as a separate aerial for the latter band will not take up much space, it is worth while erecting one. On 80 and 160 metres, the lower ends of the feeder should be connected together and to the aerial terminal. Where the main interest lies in 20 metres, the arms should be 164 feet long. By using aswitch connected as in Fig. 6, good reception will be obtained on all amateur bands. for, short: _sated a a ee wave __ broad- cast reception, the lengths quoted can be INSULATING STRIPS. \ altered to suit, eae / according to soto. on ~ oA. RECE! : ~—_ [Treg RECEIVER TERMINALS the figures i lier. patel Fig. 5(b). Folded dipole aerial, using ordinary wire and spacing insulators. Another type of folded dipole aerial is shown in Fig. 7. It calls for more wire and is not quite so simple as the ordinary folded dipole, but it is of the ‘‘wide- band”’ type and gives good results over a wide range of frequencies. The wires should preferably be separated by six inches or so, when spacing insulators will not be required. Should it not be possible to arrange wide spacing, then small block insulators should be fitted at intervals. The downlead portion of this aerial may be flat twin 300 ohm feeder or it may be constructed in the same way as that used in Fig. 5(b). The length is relatively un- “= important. RECEIVER. For high fre- quency use, it should be on the short 3 side and made € 3 fairly long for lower fre- quencies—the table given earlier can be used as a guide, re- memberingto e 300 _ OHM AERIAL FEEDER. fH id make the Fig. 6. Connections to switch for rapid change over of feeder _ overall length wires from series to parallel. equal to ‘‘a’”’ plus ‘*b’’. Page Four bi ctn deinen stiches DIRECTIONAL | On the shorter with. almost any typ CON! Fig. 7. Three-wire ohm feeder cabie is re major directional | should therefore bs With a single will be the directic The directiona arms at an angle t ALL ROUND R An excellent a trated in Fig. 8. It figure—and_ prefer: aerial is useful in cz a horizontal aerial The vertical a run from the base and it will probabl: intervals along the If electrical int wiring, it may be ac of the lead-in, the i screen earthed 2 ceiver. The additi length of cable, wt ing noise, will also, : tent, reduce the signals, and it shoul not be made any | necessary. Some s noise aerial systems length of screened;fe but then matching ers must be fitted a of the'cable, or res poor. Further, in c the interest lies in reception, these tr must be suitable waves as well as fc waves, which comf design. A vertical a receive signals eq from any directio usually slightly less to fading than the type of aerial.