WIRELESS NEWS.

Press, Volume LX, Issue 18135, 26 July 1924, Page 11

WIRELESS NEWS.

BUYING A RADIO SET. CABS AND MAINTENANCE OF BATTERIES. (snouu wairtM *on "thb mass.")

(By Electra.)

As hundreds of people are now taking an interest in radio and are buying wireless sets, some for experimenting, others for the entertainment obtained therefrem, a few hints on what to bny and how to buy it will perhaps be üßefnl. Ono must always keep in mind whea buying a complete set or parts that, as with most other commodities, yon get what you pay for. One mnst not expect to get great results from a set costing only a few pounds. Radio seta can be classified under two headings, namely, crystal and valve sets, and we will discuss the former first. The erystal set is purely for the beginner, and is not tho least bit of good for anyone who wishes to receive broadcasting stations outsido of a radius of 20 miles.

Start with a Crystal. I would recommend anyono who contemplates buying a set for the young hopeful of the family to start him off ■with a crystal set. It does not cost •i great deal, and later on, when he has the cash to invest in a valve set, quite a number of the parts can bo used, and are therefore not wasted. Nine times out of ten the young experimenter is capable and usually prefers to make up his own outfit. Tho coil or tuning inductance is made up of a few yards of copper wire wound on a suitable tube mounted on a base board. These items' can be picked up for next to nothing, and even if bought are only a matter of a few shillings. The most part of a crystal outfit is the head 'phones; these cost anything from 30b to four guineas, depending, of course, upon the make and type used. A. good crystal detector can be bought for 4s 6d, a small 'phone condenser for 28, the necessary terminals another 2s, a box of crystals Is 6d,'making the total amount of parts to be bought about £2. If one does not feel inclined or has not time to make up a simple set of this type, they can b9 bought complete from £4 10s upwards. A crystal set will nqt operate a loud speaker, but frill give, satisfactory results on local signals using 3 or 4 pairs of 'phones, but, of course, this latter means of listening to what is in tlie air is rather expensive, and to my mind it is a better idea to buy or make a two-valve set that will work a small low! speaker, so that everyone in the room, no. matter how many, can enjoy the music, etc.

Out-door Aerials. Crystal sets require eutdoor _ aerials if good results are expected, and radiophone reception with these sets cannot be effected on. indoor or frame aerials unless tho user is in fcloee proximity to a powerful transmitting station. The upkeep of a crystal set is practically nil, a new piece of crystal ba. trie required occasionally. ' t " _ For assured reception of music, eto., over long distances, a-valve set rjiusi be used. For the reception or distant broadcasting stations nsirig tne neatf ' 'phone, only a* one Or two-valve set is all that is necessary, providing agood aerial and earth are used, i Dunedin, WelHngton,'Auckllfls. Gisborne, and even .Sydney concerts are heard regularly on good jiftgle and' two-valve -sets. To be able to use .a loud-speaker in wnjundaoh. with the; set it is necessary to: Bare an outfit using at least 8 valves', generally one incorporating a detector - and two stages of audio-freqnency _ amplification. A better combination Btul is a set using one , Btage of radio frequence amplification, detector, and two of AF amplification. The Best Circuit 7

Aa to the best type of circait t6 use, one could fin ana oolumns on this subject, and therefor® X do not intend to touch on that poiat in this article, except to advise prospective buyers of radio gets to' make rare that the outfit they intend buying is using a circuit that is approved by the Badio Inspector. Another point to watch in respect to eweurta is to make' sure that the set has s useful wave-length range. For the ftcaption of broadcasting stations only a . wave-length range <>f 240 to 450 niPtres is required, but if one wishes to/receive tne time signals transmitted from -the Wellington station at 10.30 sum. every day and Tuesday. and Friday evenings at 8.30, the set mtist be able to go up to the 000 metre . wavelength. The ; ideal set is that with a from 240 metres to 600 metres. I know it is' a hard -problem for'a person starting into radio to decide what type «j€ set to buy, " jf*# Are a great number on the market all claiming to be better than the Qtner ielkm-. To mv mind the best plait for a person so situated is to join ft. locs* radio (society and enlist the aid of it« members before! spending much money on a wireless installation. It is: aleo well to go to a reputable dealer when purchasing apparatus. . If communicating with radio firms-by letter concerning the installation of a eet t a statement should be made regarding the amount of space available for an outside aerial, and, whether reception is desired by means of head phonea or by -a loud speaker. The enquirer should also state whether he wishes merely to receive the broadcast P™" grammes transmitted by broadcasting stations, or whether he wishes to do able to obtain the time, signals from Wellington, also aa to what range to® wishes to cover. The dealer or company will then be able to suggesttho best arrangements in paiitcul» circumstances. For those who have the facilities for doing so I would recommend j them to build their own nets as on® j will have « far greater knowledge ot the construction of a set and tne uses j of the various parte than would, in buying one ready mad®. Half the pleasure m radio is obtained by buuding one's own outfit and not only that "but one can build it to suit one a own requirements. i _ . In conclusion I would advwe all to 'buy the best they can afford and see that you obtain your apparatus from a firm which values its. reput»tio«i\ahd cannot afford to sell you a seiorpbrts which will not work • properly. One cannot expect the some security ... in dealing with an unknown firm or one of little experience as he would obtain in dealing with a recognised company who rave a reputation to uphold.

CARE OF THE BATTERY. The most important pomt to in mind ijß thai "the (battery qotation, known as the electrolyte, must, cover the . plates. This., eolation evaporates and should be' replaced 'wiih distilled waiter. Tbd fluid shouldreach tip'to about one quarter inch above tne plates,—above all, do not flood. - ■ Batteries should be kept i" ,» dry place. Keep aU artwhe^Blpeoiuly metato. out of and away tttm thThattery. nerions. coated, with vaaelme so as to stop corroaw®. Ifjj» tion ia BjaßedC- wipe with adothdi?p«a in ammonia water- „ , . i . 1 The battery: should aJwaya ne XSOT well' charged*, To aawrtaaiv|t> coadi-

tion, test the specific gravity of fie solution in each cell with a hyafoeiefccft The reading will indicate th» comfit** of the battery aa follow*: 1275 to 1300 fully charged; 1175 to ISOO half charged ; below, 1150 discharged. Direct Cmimt Only. "Dee only direct current for charpag. If only alternating current is available, it is necessary to nso sow* sort of a rectifier to convert the AC to DC. Storage batteries are rated according to the number of ampere hour* ttwy will discharge at the rate of one s»pere per hoar. For example, a6O ampere boor battery has a capacity of ea* ampere for 60 hour*. If tho rate e£ ampere drain is increased to two «8pens, tho number of hour* reanirai to discharge tho battery will w» 3D hours. Seasons for Charting. Tho battery used for radk> bo frequently charged for the following reasons: First: Frequent charging feecpa th# voltage of the battery near its nan* mum (something orer si* volts). (&*• inc: better results on the reNtmnjt tubes. Second: Frequent chargmcr K«*pß • reserve capanty always avsHsfck* w*iH» would not he so if a battery were allowed to reach tho disf-hargo point before charging. As to just what ''frequent charsifWf means —this depends npon the antfrtf* hour capacity of the hntterv and th* ! nnmlicr of receiving tnKes osed. Assuming that tho receiving set mw* 8 tnhes (a detector and two amplify?* 1 and the tabes are of fhe _*tanAt?4 •American type, this set will tafa tbrpe-qnart»r« of an ampere pet* hovr. If it ia used two hours Tier d«V tfwatt* nere hours drawn frnm the batterv «W> H 2 nr 11 nmpeWs pet dar. If til# battery i»sed is a 60 ampere hour on* and as it is not wise to discharge'* * battery fully it will be neeessaTT t# recharge it at least once a mootft ( Charging Bote. There are limits in enrrent at trhtdbf a battery should be charged. Th» makers usually state the charp«|C rate on the battery itself, as it ia meet important. A4oto AO ampere fctiov battery should not he charged at etwCt .over 2 amperes, while as 80 ampere hour or larger battery caa be charged nt 5 amperes. Give your batterieeall tho rare and attention that yon can i it will pay yon. This applies to totfe "A" and the rechargeable type ,r ß* batteries. CORRESPONDENCE. W.E.8., Riccarton. and J.A.IL, Bedcliffs.—l have forwarded .the dreaft of the Etherphono set under aapctftte ' cover. I trust ton will be able «» ptrt the hook-op to work u MtWietwgr as it does in-the made-op oot, Questions will be answered and •&§- gesrtiona given on Radio natters Jvr readers of this column. AddrtMi *3 correspondence to "Electra," e,o. tits Editor, "The Press," Christdmreb,

His Eoyal Hlghfi&a th« Trfrntc . M Wales has written a'letter of moor mendation for a volume eatttlft! "Scout Pie," which Messrs 0. Afttttr Pearson, Ltd., are publishing. It J& been edited by Mr Ernest Young OB behalf of the Boy Scouts* Acaxfati**, for the benefit of whose fonds the ««rk is being issued. It will form 41 some presentation vohrme, and tfretjr copy sold .swells the funds of thai deserving movement, the Bay Association. According to the superintendent of the periodical section of the New Public Library that department U largely utilised by persons lII' practical suggestion* tot poses. Typiea! question* aafced *f im - desk are: "What magazism hArtymt on making and Advertising &&&|r"; gnmf" "Where tan J fbtd Jaffa*** . tion on the way egg boxas ar»sa«fer' The head of one firm haa far most years culled designs for hie ia««s 6W» a wide range- of art- magnziMi, demand ' for moying-picture far exceeds that for any titff With the exception el rtw s readers who ask for 1 from {Booth American atatyr* t ins trsde methods. " A S • ■ -i iiiirin -