REPEATER DESIGN — NEWFOUNDLAND-NOVA SCOTIA LINKS 261 



niques can be effectivel}' employed, e.g., by using double connections. 

 Over 1,500 separate soft-soldered connections are involved in the com- 

 plete assembly. Much work has been done on components, but only a 

 brief indication can be included here. A range of typical components ap- 

 pears in Figs. 4-6. 



Resistors 



Resistors fall into the following categories: 



(o) Power resistors used solely for dc purposes (e.g., resistors provid- 

 ing the amplifier high-voltage supply). These are wire-wound vitreous- 

 enamelled resistors on Sintox ceramic formers. Nichrome terminal leads 

 are used, and all connections are brazed. 



(h) High-frequency resistors whose tolerance is not close, and often 

 carrying direct current but of low power (e.g., anode load resistances). 

 A modification of a standard carbon-rod resistor is used. The ends of the 

 rod are copper plated and the end caps and terminal leads are soldered 

 on. The tolerance is normally ±5 per cent, and the maximum rating 

 permitted is about one-quarter of the commercial rating. 



(c) Precise high-frequency resistors of resistance below 1,000 ohms 

 (e.g., feedback components). Here wire-wound spool resistors are suita- 

 ble, and bifilar or reverse layer windings with Lewmex enamel and silk- 

 covered wire are used. 



(d) Precise high-frequency resistors of high resistance. For terminat- 

 ing the input transformer a resistance of 17,000 ohms is required. Because 

 it is not possible to make a suitable wire-wound resistor, high-stability 

 cracked-carbon film resistors are used, but to minimize the effect of a 

 disconnection two are used in parallel. 



Inductors 



The majority of inductors used in the amplifier and equalizer do not 

 require a high Q-factor. They are wound on air-cored ceramic bobbins 

 of four types, and the high -inductance ones are sectionalized. In general 

 solid wire with Lewmex enamel and double-silk covering is used for the 

 amplifier mductors, and stranded wire for the equalizer inductors. 



A high Q-factor inductor is essential in the directional filters, and a 

 carbonyl-iron pot core was used; the Q-factor is about 250 at 300 kg, 

 Precise adjustment and stability of inductance was obtained by set tins 

 the gap between the halves of the pot core with a cement of Araldite 

 (an epoxy resin) and titanium dioxide. A Perspex former was used. 



Special inductors were required in the power filters to take the 316-ma 



