WIRELESS

Wanganui Chronicle, Volume LXXXII, Issue 19366, 24 July 1925, Page 10

WIRELESS

By

The Grid

'The Why and tihe Wherefore. I In this article, which will be the last jof this series, we propose to deal with : the 4 ‘B” battery and the telephones, [which are the only portions of a single 1 valve set not yet discussed. It is not !proposed to go on with these articles ■ into the realms of high and low fre[quentcy amplification unless our readers express a wish that wo should do Iso immediately. We should prefer to leave these subjects until a. later d'ate, [when we hope to publish diagrams and • • full details of an efficient set combinjing both high and low frequency amplification on the reflex principle. This type of .set is undoubtedly destined to prove extremely popular, since it provides U maximum of signal strength with a minimum of expense. Before giving details, however, we desire to 'test out the, circuits and will leave the matter over until this has been done. With regard to <4 B” batteries, the average amateur usually purchases his battery and trusts very largely to luck as to the results he obtains. In this country wc arc at a grdat disadvantage compared with residents of ■America and England, in that the •“B” batteries we use till have to come a long distance under bad conditions. [The small dry cells of which almost ‘all “B” batteries are composed, are [very apt to deteriorate if kept in stock, ' especially if the climate is hot. In , coming to New Zealand the batteries I have to pass through the tropics, and i unless stowed in a suitable place on the ship, are apt to be affected by the [hdat. This fact is, we believe, an explanation of the varying quality of batteries made by the same inanufacturI ers, and exported to New Zealand. A ; Ditch of batteries which is despatched 1 shortly after manufacture and travois [quickly to New Zealand in a suitable I position on the ship, will usually arj rive in good order and give good serI vice, while Another batch which has j been delayed in America and badly stowed on the ship, will give very poor | service. Unfortunately the amateur has ’little control over these matters, and lowing to the distinctly unsatisfactory I mature of the wireless trade on account l of the broadcasting bungle, he is prac[tically forced to take what he can get in the way of apparatus generally, in- | eluding “B” batteries. This much he can do, however, and that is to .insist ■that every battery he purchases shall ' >how on test at least its rated voltage. A single dry cell in good order I should, when new, show a voltage of 1.55, land therefore a 22'. volt “B” ■ battery should show 23.25 volts or 'thereabouts when in first-class order. [lf such a battery, when tested, shows '23 volts or over the purchaser can bo fairly confident that it is in good order. ; A 45 volt battery should show 46 to: 461 volts if in good order. If a bat-i tery on test shows below its rated voltla go it is probably in bad order, and the purchaser is justified in rejecting it. These remarks are made with all due respect to the wireless dealers, who are only too ready to test the batteries if so requested, but who will often not trouble unless the purchaser asks them to do so. The dealers themselves arc bound to incur some loss through 'faulty batteries, but their loss should Ibe passed hack to the wholesalers, and [not down to the purchasers. n B”l 'batteries are a. gamble for everybody land each party must protect itself as best it din. A 221 volt “B” battery consists of 15 single smbll dry cells connected in series and embedded in a wax compound. Taps are usually taken out to provide voltages of 161, IS, 19A, 21 and 224. Each small dry cell consists of a centr*ril carbon rod, surrounded by a depolarising agent such as Manganese dioxide. Outside the depolarising agent is a porous container made of cardboard of cloth, and round this is a paste of glycerine and zinc sulphate with certain other components which are more or less trade secrets. Outside the paste is a zinc container The top of the cell is usually sdalcd with a waxy sealing compound, although in some cells pitch is used. Although the cell is called a ‘‘dry' cell it is not really dry, otherwise it could not function at all. The paste is clamp and must remain so while the cell is in operation, while the depolarising agent must also be slightly moist. The cell functions in the following manner: The paste contains chemical combination which attack the zinc outer dase, releasing negative electrons as a result of the chemical reaction. The negative electrons accumulate on the

zinc while the paste becomes positively charged, i.e., it has a deficit of electrons. If, now. the zinc and the carbon are connected st current of electrons (or in other words electricity), will flow from the zine round the connecting circuit back into the carbon and so to the paste. It is commonly imagined that the current flows from positive to negative, but this is incorrect, as we have explained previously in these pages. A positive charge is rccilly an electrical vacuum, which lends to attract electrons from any body having a less positive charge. A negative charge is an excess of electrons, which tend to flow to any body less negatively charged. Now. as before stated, it is essential that the paste shall remain moist for the cell to function properly, hence it. the paste dries up trouble is bound to occur. If a cell is subjected to heat the paste swells and leaks out of the top of the cell, thus allowing air to enter and causing evaporation. If the paste cannot get out of the top it will often force its way through the zinc case. I with equally bad results. Any cell that shows signs of paste leakage |should be discarded. We strongly advise amateurs to purchase their 44 B’’ batteries in 22X volt blocks, since if one block goes it c'an easily be replaced, whereas if 45 volt blocks arc purchased the whole block may have to be discarded because of a few bad cells. In some cases the 45 volt blocks have a tapping at 22V volts, and if one half goes the other half can be

.used, but this is not always satisfac-I j tory, since one bad cell may start the I whole lot going. “B” batteries should [never be short-circuited, Und should be i [kept in a cool, dry place when not in' j use. It is good practice to connect a [ [ large condenser, say 4 to the micro- I farad, across the “B” battery, as this provides a path for high frequency I currents and assists reaction. Regarding telephones, there is -nor i much to be said. The best advice we i can give the amateur is to purchase ■ the best pair of phones he can afford. | since bad phones arc neither use nor 1 [ornament. There is a special tvpc’of phone employing a reed instead of the usual iron diaphragm. This type gives I excellent results und is well worth the extra price, especially on weak sig ! nals. For ordinary everyday use the [iron diaphragm if well made is fairly [ siat is factory, but for special work the : reed phone is head and shoulders above [it. Good phonos are usually marked, i either on the phones or by different 1 coloured cords, so that they may be | correctly connected to the set/ The ; positive, cord should always be connect|ed to the positive of the 4< B” battery. | The object of this is to ensure thtit tlx* [current flowing through the phones will • not create a magnetic field opposing i the field of the permanent magnets, [which would tend to weaken the magnets and thus lower the sensitiveness of the phones. If phones are not marked in this way they are usutilly not of very high quality. As regards resistance, the most useful value is 1000 ohms per phone, i.e., 2000 ohms for the .pair. This value is practically always adopted nowadays. .Amateurs are strongly advised not to remove the earleaps on the phones, as the diaphragm I may easily be bent and seriously dami aged. The Almost unversal desire to I see the inside is quite natural, hut wo ' recommend you to perform the opora- [ lion on a friend’s phones, rather I than on your own. 1 The Broadcasting Position. i Amateurs throughout the country [ will no doubt be keenly interested in I the announcement mude on Monday I last that a contract had been entered i ; into with the Government for the ereu- [ , lion of two SUU watt broadcasting , stations in New Zealand. Complete j details of the agreement were given : ion Wednesday by the I’ostmasterGeneral (Sir James Farr). Two sta- I lions are to be erected within six I months, one in Auckland and one in I ! Christchurch. When these stat ions tire l in operation the licensees must, if re [quested by the Government, erect two [additional stations, one in Wellington [and one in Dunedin. The persons who 1 have entered into the agreement,: I Messrs W. Goodfellow and A. R. [ I Harris, undertake to form at once, a ' ' company which will ratify the agreement and assume control before March 31 next. This company will have a capital of £20,000, in 20.000 shares of £1 each, and ton per centum of the shares must bo held at the disposal ot the. Government. The dividends to be paid by the company are limited to 7/ per centum per annum free of tax, and before any dividends can be p.iid provision must be made for Ihe establishment and operation of the broadcasting stations, the purchase of new apparatus, the provision of suitable programmes and the payment of ordinary’ working and operating expenses. The revenue of the company wdl be] such payments as may be arranged out of a fund to be set up by the Government, and to be made up of £1 -»s out of each receiving license fee. and 90 per centum of dealers’ license fees. The contract with the company will be for a period of five years at the end ■ of which time the Government will, j if the contract is not; renewed, pur- ! clia.se the apparatus at a. figure to be agreed upon or settled by arbitration. The Government is at present paying a subsidy out of listeners’ fees amounting to £.15 per week to each of certain existing stations. This subsidy is to be continued until the now stations are in working order, provided that the ex isting stations are prepared to continue broadcasting. If not the new company is bound within throe months to take over such of the existing stations as are prepared to sell their plants.

The Postmaster-General referred to the criticism which h'as been levelled at his department because of the fact that the license foe of £1 10s has been charged since April I last. His defence of the action of the Government is, w’o are afraid, somewhlil. weak. lie stated that it must not bo overlooked that for two years listeners have received the benefit of the present broadcasting service without any payment except a fee of ss. This is not strictly correct, since the present service htid not been in effective operation for two years prior to April 1 last. Furthermore, the increased license fee was charged on the understanding that a better service was to be provided, ami this service will not bo provided until January next, ton months from the date of the now regulations. However, it. is pleasing to see that the tangle shows some signs of being straighten cd out, and by next year listening-in should be worth while in New Zealano. There is one point, however, which

I rather looks as if it will cause trouble. Hundreds of amateurs in Wellington I have installed sets in the hope that [ a powerful station would be erected [ there at an early date. It appears now I that Wellington is 1o take la back seat I in the broadcasting line and no doubt howls of anguish will arise from all concerned. Since, however, the origin I al syndicate, which had its headquarters in Wellington, failed to reach any (finality with the department although 'negotiations were prolonged for a con- | sidcrable period, it. is somewhat, natural . that the agreement which has been made should bo in the interests of the 'centres whose residents have concluded I the arrangements. General Notes. ; Apropos of the broadcasting bungle I in the country, the following figures 1 may be of interest. The Postmast er'General in Australia recently announced that to May 30, .1925, la total of (61,51 s receiving licenses had been issued in Australia, of which 33.964 had ■ been issued in Now South Wales. The ‘ total revenue collected amounted to £113,658. The apportionment to the 1 various broadckisting stations was as •follows: Farmers’ Ltd. (2FC), £34,628; I Broadcasters’ Ltd., Sydney (2BL), £12.018; Broadcasting Company of Australia Ltd., Melbourne (3LO), £14,,444; Associated Radio Co., Ltd., Mel- • bourne (3AR), £1089; Westrali'an Far

mors’ Ltd., Perth (6WF), £4220. In 1 the United States it has been reported that although no license fees are charged, the revenue of WTIN, of New York, is £60,000 per Innnum. while that of WFBH in the same city is £1(5,000 per annum. Those amounts arc de I rived from the hire of the stations for ■ indirect advertising and propaganda purposes. Local amateurs will no doubt have noticed very severe interference by certain Morse Stations on 3LO’s wave length. The interfering signals come from the Ameridan Fleet, which is now nearing the cost of Australia. Until the fleet departs it. is probable that the interference will continue. ■ Talking of the American Fleet reminds us that several reports have been published lately referring to the exceflent short wave work being done by Lieut. Schnell, on the worship Seattle. Lieut. Schnell is only temporarily attached to the fleet, and before he left was the traffic manager of the American Amateur Radio Relay ’ Lohgue. The credit of his work belongs • entirely to amateurs who have done so ‘ much research work on short waves.