WIRELESS NEWS.

Press, Volume LX, Issue 18237, 22 November 1924, Page 11

WIRELESS NEWS.

—-♦ LOOP AERIAL SETS. HIGH EFFICIENCY NECESSARY. (specuiat wmttbh poa "m ntess.") (By "Electra.") . Reports of tho infinitesimal amount of energy received by a radio loop, as described at a reoent meeting of the American Chemical Society, strikingly illustrated the, importance of- the condenser in a receiving set. , A calculation niado of the amount of power picked up by a loop, one foot in diameter, . in a laboratory in New York State, receiving radio impulses from San Francisco, indicated that it was equal to only one billionth of a fly-power. The energy set free by a house fly climbing up a wall is said to be equal to the amount of energy the loop would'receive in a continuous period of tlurty-fivo years. Yet loop reception is efficient and increasingly popular. Its efficiency depends to V great extent upon the variable condenser. To be efficient, the condenser must not waste energy. A wasteful condenser is as bad as a leaky hose. If a condenser, which in a loop set is placed between the loop and the amplifier, wastes power, what chance has it to pas® enough energy through to the ampnfier to build up an audible signal? " . Yet. strangely enough, the public lias been slow- to realise that high resistance in anv.part used in a set results in serious loss of received energy. During recent months the value of efficient condensers has been emphasised, and buyers are now demanding them. Many manufacturers aro bringing ouj new condensers. Somo are better than others, hut there is no quostion but that a tremendous improvement has been made.

One company, for example, has gone so far into the subject that it Bilverplates tho plates to reduce resistance; a cover is providod to exclude dust and mosture, a pigtail connexion is used, and hard rubber insulation of lsw de-electrie loss further helps to prevent losses.

Gratifying progress has been made in reducing losses to a minimum. With low. losses and sharp tuning, practically, all tho currents on the antenna or loop can now be used. . . The efficient set conserves ' energy; Any lqop or outside antenna reecives only a little. ! Don't waste it, Ono way to Btop leaks and waste 1b to use the most efficient condenser obtainable.

HARD AND SOFT VALVES. The . terms "hard or soft" as applied, to wireless valves are confusing to many' amateurs. The "hard" valve is one which has been exhausted to; a perfect vacuilm, whilst'a.".Boft" valve is one which is not so near exhaustion. It would. be df'great interest to consider wliat would happen in a valve containing a certain amount of gas. Tho electrons emitted by the filament travel at' a high ' velocity, and if an electron travelling at a high speed should collide with, an- atom of gas, the impact might be sufficient to detach electrons from" the gas atom. Such detached electrons would'join tho main electron flow, thus increasing the plafe"current. 1

• The softer •; the v valve . .the more chances there'' ate of such jjollisions, and the - largeir the- plate current : for any given conditiona.of filament temperature arid . poteiitial, • and plate potent!^.,. . w ( . • ,On the face of it, a soft valve would appear, very desirable. Unfortunately, however, the advantage of increased flow is only attained af.considerable sacrifice in other directions. The gas atoms, after, collision,,, with electrons,, {ire. lef£ charged. .These positive '•'*ions" are attracted to the filamfetft attaining sUcK *a velocity, that they'' ' bombard '' the filament with a violence which wltimately breaks. it down; ■ Therefore, although'ipossessing certain advantages in. that, fori a given battery power," larger flow'can be obtained, risoftvalva has a" Very- short life. Hard valves, on the other, hand, while.requiring larger battery, power for a given ! effect, have a, long -life and are therefore almost' exclusively. used io-dayy

BRITAIN?S NEW STATION. | The largest wireless station' in the world, is. now being-built at Hillmorten, near Rugby (England). ; Tiers will be twelve steel masts, 820 ft high, which will carry an aerial a mile long and half a mile wide. . ' ■' VALVE CHARACTERISTICS. Myres Valves:—"A" Battery, dry battery type 8 volts, Hi Mu ,type 4-6 volts; filament current, .25 amp, >6 amp; rheostat, 30' ohms, 20 ohms;.* "IB". battery detector, 12-45 .volts, 12-46 volts; "B" battery .amplifier, 45-300 volts, 45-300 volts; "C" battery (if used) 8 volts, 3 volts; grid condenser, .00025, .00025; grid leak, 2 megs, 2 megs; plate current 22$ v, 2 i .m.a., 2J m.a.; plate current 674, 5 m.a., 5 m&.; amplification constant, 5-6, 9; mutual inductance, 5-6, 6-7. ' '■ ■ Badiotrobs. "A" battery: WO 11 and 12, 1.5 volts; UV 191?, 4.5 v.; UV 200, 6; UV 201 A, 6. . , . . ~ Filament current: WO 11 and. 12, .25 amp; UV 109, .06; UV 200,1; UV 201 A, .25.' ' '..■vv-.:.: ' Rheostat: WO 11 and 12, 80 ohim; UV 199, 20 ohm; UV 200, 6; JJV 201 A, 20 ohm. "BV battery, detc,: WO 11 and 12, 20-45 v; UV 199, 20-45 v; UV 200,15-24 v; UV 201 A, 20-45. ■■■•' 1 "B" battery, amplifier: WO 11 and 12, 40*100 v; UV 199, 40-100; UV 201 A, 40-120 v. Grid condenserr WO 11 andl2, .00025; UV .199, .00025; UV 200, .00025-0005; UV 201 A, .00025. ' Grid leak: ? WO ll- and 12," 2-3 mess: : UV 199, 2-9; "TJV 200, J-2:'UV 201 A, 2-9. . ■ ' ' • V - ' '' ' ' Plate current, 20v: WO 11 and 12, •3ma; UV 19£ L .25; UV 200, .25-1. Plate current, 80v: WO 11 and 12, 3.9 ma; UV 199, 3J; UV 201 A, 4.8 m.a. Plate current, lOOv: UV 201 A. 7.5 m.a. ■ Amplification constant: WO 11 and 12i 6:S>:UV 199, 6.25; UV 201 A, 8.0. . "E" battery at 4Qv. plate voltage: .UV 201 A, .5-l.Ov. . 60v plate voltage: WO 11 and 12,1.5; UV 199, UV 201 A, l-3v. 80v plate vdltage:-WO 11 and 12, 3.0; UV 199, 4.5-6; UV 201 A, 3-4.5 v. IOOv plate voltage: WO 11-and 3.0; UV 199, 6-7.5; UV 201 A, 4.5-fiv. 12a plate voltage: UV 201 A . * Note.—loo volts on plate of is not recommended for ordinary . vice; 80 volts should not except in very special . ?e _ i UVI99 and 201 A tubes i sistance between two gBWOF k. horns is nina A resistance battflr for .very megohms w somewHOT m* weak, signals* . , , / \ RS.C. - Jj e „tin2S of the above Society started/ apd are held every I eveming at 7.30 o'eloek in -*«•*

ono interested in radio !s hsvttsjd t» Is* present HERE AND THESE. A new radio record was esiafeKssl«»2 when tho Chelmsford bro*iSe*fi&ing station, tho most posrcrfal ia England, was heard in Algiers oa a crystal set. The station was leaaai with perfect, clarity. The aodtaiatiwai was perfect, and every -word of t&» artists could tvo easily weagaiswiAlgiers is about 10OQ inilf* fwas London. Estimates by the Deportees* «f Commerce (U.S.A.), based on £r»4 six months of 1924. are that ssmhp® tkata 500,000.000 dollars' worth of «di» apparatus will be exported #kh» t&at country this year. This Sgnre %«* ,a new record, and will pS&ee" Ta4io-a»-paratus among the leading experts of the country. English radio users were greatly «*- lieved when they got & legal cpsaSaa to the effect that the owaer af a cannot prevent a tenant from setsiajj |up a wireless mast oa the jwesuaMii but if the tenant does damage in d«*S so then he is liable for the dxssags* done. The third edition of the "Rad» nal" is now out, and ta erory bit» gpssd as its predecessors. A very iafeemss*ing article on "Grid CMttesfeT Jtectekcation." by H. P. V. Brawn, s&waH W read by all, also the tips ca grid tew* by E. \V. England. _ Great interest is being taken ia WEada in tho matter of radio aids s»ragation, and considerabfo provess s#* been made in this direction. life®* aw* now in operation in Canada ex beacons, which » mow than ia ass? other country except the F-S-A. A»otlier radio beaeoa is aooa to b» lished in Canada. T%ew> atm mm m operation seven radio compass statieos on the shore. A local radio Sroi has brc-oget aa% a very fine idea ia radio switch®*. In*ta»d of having to buy studs, stop®, mratdharro, and knob, one can cow get tl® ■whole thing in one nnit, from a S*» point to a nineteen point rsritcfe. H» unit mounts behind the panel «6£ tbw* a single hole mounting. HINTS AND TIPS. Clean away any excess taidams paste from the terminals o£ jsw with alcohol, and thus sat© yattnsefif » lot of time and trouble in Caring what ia wrong with jow Mi To. prevent ywur aerial. «op«* feggK rotting, and to rnako them tfeawHSgWj* waterproof, work talknr info tfcjßi thoroughly, and thus e&v® thft asyMM* of specially prepared.rope. 'By the following method osi fay cells may be turned into asrv»»> able wet batteries, lb dry ally consist of a S-iech shsefc m tho outside, followed hf tbo faute, asd then tho carbon rod in t&e eesftrav rounded by a bag of m«wganw» dwrife. Carefully remove tho aiao c*Ba*fc:'«ad clean it thoroughly, afterwards it in a jam jar with sal' amaaaaiaa «Btttion. Thus you wili get a tfawp battery of abont H volta.