RADIO NOTES

Manawatu Standard, Volume XLV, Issue 287, 7 November 1925, Page 6

RADIO NOTES

THE ACCUMULATOR

(By “Q.R.M.”)

Tim accumulator, or A battery, is one of the most important parts of a radio receiving set. Strange to say it is also the most sadly looked niter part of the whole set. Much of the socalled static has often been traced to a badly looked after battery. The most critical period in tho life of an accumulator is the time alien it is receiving its first charge. This is Lko time when it is either made or marred, and consequently the utmost I care should bo given it. First charge. —The maker’s instructions should bo first read thoroughly and should then bo strictly complied with. Particularly should care be taken in regard to the density of the electrolyte and the rate of charge. We will assume that, when a cell is being charged acid is driven out of the plates and absorbed by the electrolyte, and when discharging the electrolyte gives up its acid which again enters the plates. This increases or decreases the specific gravity. A new cell, when first filled with acid at a specific gravity of 1200, when left standing for 12 hours at least will absorb into the plates most of the acid from thp electrolyte which will read sometimes below 1100, thus showing that the battery is “dead.” The battery should be charged immediately or sulpliation will set in. If a very low rate of charge is given, the S.G. will at first decrease, owing to the acid action being more rapid than charging action. After a long charge, generally 48 'hours or over, tho S.G. will rise to the normal reading for a fully charged battery. Often when the first charge is finished, and tho plates gas freely at a low charging rate, the S. G. will be lower than 1000, or the correct full charge reading Jf this is persistent it may be corrected by adding raw acid, but this should not be resorted to until tho battery has received three full charges, in which time the fault may by , corrected.

Some batteries are fully ..charged at 1200, but usually 1000 is the proper reading. Care should bo taken in diluting the acid. Only distilled water and pure sulphuric acid should lie used. Four parts of water are first poured into a stone or glass vessel, and,' afterwards, one part of sulphuric acid is poured slowly into it, after which the mixture is thoroughly stirred. Never must water be added to raw acid, or serious results may result with serious injuries to the operator. Tho diluted acid should then be allowed to cool off. When cold, test with hydrometer, and add distilled water or acid to correct tho gravity. Acid must always be checked for 1 density before filling the accumulator, as it is very difficult to correct it when once it lias been placed in the battery. The acid is then solely dependent on the state of charge of the plates, and it will be exceedingly difficult to accurately determine whether the battery is fully charged, if the acid was incorrect before being placed in the cells. if aif accumulator is to be emptied and left standing for a time, the usuul method adopted is to first discharge the accumulator, until the S.G. reads ' 1200. Then pour off the fluid and dry tho cell. When the battery is to be filled again, acid of exactly 1200 S.G. should be used, so that it will commence operating at the same rate as before. A ever should the cells be washed out with boiling water, as this has tho most disastrous effects both on the celluloid casing and the lead grids. For testing an accumulator for charge, the hydrometer test is the only reliable one. Care should be taken, however, that the acid was correct before being placed in tho cell or a test, reading 1000 may really only bo at half charge. If this is suspected, connect it at half the usual charging rate, and when the gravity lias exceeded 1000 draw off some of the acid and replace it with distilled water, repeating at intervals, until the density remains constant at 11100 for a six hour charge. There is a great difference in opinion over whether thick plates are better than thin ones. The advantages usually given in favour of the tjiick plate type are: An exceptionally steady discharge, long life, freedom from sulpliation and strong construction. A thick plate accumulator is very misleading in regard to its testing, if anyone is not acquainted with its peculiarities. Jf charged 'at a fairly high rate a hydrometer test may read 1000, and when tested again next morning only show 1225. A thick plate accumulator, with a stated charge of 4 amps, will often come up better at 2 amps, although the length of charge will, of course, have to be doubled. A thin plate battery can be charged much more quickly, and consequently is favoured by many radio listeners-in. The thick plate type is strongly recommended for dull emitters. Never upon any account must an accumulator be “tested” by means of placing a piece of metal or wire across the terminals to gauge the strength of tho spark, as this will very quickly ruin the whole battery beyond any hope of restoration. VARIOUS TOPICS. Britain is now spending approximately £10,000,000 a year on wireless, giving employment to over 35,000 workmen, both skilled and otherwise. Every amateur who lias an accumulator should keep a bottle of ammonia bandy, as it will quickly neutralise uny acid spilt upon tho clothing or carpet. New Zealand radio fans will shortly have an opportunity of hearing what an exhibition on a large scale is like. All tho noises associated with an exhibition are to be broadcast from Dunedin shortly. Besides broadcasting the bands, orchestras, etc., all the various noises of cheering crowds, of the scenic railway trains, the laughter of happy people, etc., will also bo broadcast.

Two 100 fpot masts aro to be erected on tlie exhibition grounds, with a span of 500 feet. A T. aerial will be slung between them. The power to be used will bo the full 500 watts. Practically all the initial arrangements have been made between Mr J. M. Bingham, controller of technical work for tlio Radio Broadcasting Company of New Zealand, and the exhibition authorities. A report from Virginia states that a man was found on the shore at Capo Charles, whom no one was able to understand. Various people, who claimed to bo ablo to recognise any language were unable to comprehend a word he said. Some one sugg6sted broadcasting him. He was then taken to a broadcast station and by signs told to spoak into the microphone. His language was correctly recognised by one or two persons listening-in. He proved to bo a native of Lapland to where ho was finally taken to his anxious relatives. The local club is slowly reaching the time when transmissions and meetings will be able to be continued. A great deal of difficulty was experienced in putting up the aerial, macts and counterpoise, the work proving' more

difficult on account of the few members who turned up on each occasion to do it. The half-dozen .members who had sufficient enthusiasm, and who were sporting enough to undertake the difficult work, aro to bo congratulated on their success, considering the hampered conditions under which they havo been striving. With sufficient hands, the work could have been completed in less than a fortnight and tlio station could have been back on the air days ago, but just because the listeners-in in this town have not sufficient “go” in them to support the work of their club, tlio time had unavoidably to bo prolonged. Every one will listen-in on the Ration when in operation, but if a short two or three hours’ work is required to improve and altor it, no help is forthcoming, except by a few.