. Condizioni di valutazione QST . Costruzione si noterà che è previsto di racchiudere completamente i tubi e i circuiti dei serbatoi. L'involucro ha due scopi: Prevede un percorso per la circolazione dell'aria di raffreddamento, e la radiazione di holdsdown dai circuiti dei serbatoi. La considerazione di Thelatter è importante per ottenere •• World al di sopra di .JO Mc, QST. Ottobre, 1951, p. 13G. L'alimentazione nella linea di trasmissione e della schermatura di cortesei è un aiuto alla prevenzione di TVI. Il telaio principale è dotato di un coperchio inferiore.l'aria proveniente dalla ventola montata sulla parete posteriore circola intorno al tubo del triplicatore, in corrispondenza delpiede, e.
1883 x 1326 px | 31,9 x 22,5 cm | 12,6 x 8,8 inches | 150dpi
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. QST . rating conditions. Construction It will be noted that provision is made forenclosing the tubes and tank circuits completely.The enclosure serves two purposes: it providesa path for circulation of cooling air, and holdsdown radiation from the tank circuits. Thelatter consideration is important in getting •• World Above .JO Mc, QST. October, 1951, p. 13G. power into the transmission line, and of coursethe shielding is an aid to TVI prevention. The main chassis is fitted with a bottom cover.Air from the fan mounted on the rear wall iscirculated up around the tripler tube, at theleft, and through J^-inch holes below the ampli-fier tube. Holes in the top cover are the onlymeans for this air to escape, and thus the coolingflow is concentrated where it will do the mostgood. The number of holes in the top cover, and in the chassis under the amplifier tube, can be varied until an equal flow of air appearsto be coming through the two top sets of holes.This can be checked readily by noting how. briskly a sheet of paper rises from either setof holes when the fan is started. This checkshould, of course, be made with the bottomplate in place. The fan shown provides a flow of 17 cubicfeet per minute, more than adequate for thejob, so no great care was taken to stop smallair leaks. Where a smaller fan is used, all airholes should be plugged. Small holes and crackscan be sealed with household cement, and themeter jacks should be plugged in this case. The tripler tube is mounted vertically, atthe left, with its socket 13^ inches belowthe chassis. There is just room under the socketfor the self-resonant input circuit, L2. Theamplifier tube is horizontal, with its socketmounted in back of a plate that is 8 inchesfrom the left edge of the 3 X 4 X 17-inchaluminum chassis. The shielding enclosure is3}/4 inches wide by 3}^ inches high Half-wave lines are used in all 432-Mc.circuits. The grid circuit of the amplifier is capa-citively coupled to the tripler plate line, the twooverl
