Notes and Hints

Sun (Auckland), Volume II, Issue 343, 2 May 1928, Page 14

Notes and Hints

ORPHAN SETS The recent auction, sale of wireless goods in the city should be the cause of new licences being taken out, as all the receiving sets were quickly sold out. Many of the sets seem to have been samples and therefore "orphans,” and the writer urges those who bought them to write to the makers for advice and descriptive matter. This will save a great deal of trouble and expense when the sets have to be repairedA REMUERA COMPLAINT There have been several complaints lately of a very bad form of interference in Remuera, and in the neighbourhood of Mount Hobson it is very pronounced. The interference is a fairly high-pitched note, varying in intensity, very broad but increasing in strength as the wave-length is decreased. It breaks in suddenly and dies out gradually. The writer would like to hear of others experiencing this complaint so that some action may be taken. AN INTERESTING ACCESSORY An official Browning-Drake “booster" is coming here shortly. It consists of a stage of screened grid R.F. amplification similar to that described in The Sun a few weeks ago, but is a single unit and may be placed in front of any existing set and connects merely to the aerial terminal of the set, whether it be valve or crystal. The complete radio fan -will now have his R.F. booster, his short wave adapter, his output filter, gramophone pick-up and gramophone speaker adapter, truly a formidable list but a very interesting one. ADDING AMPLIFIERS TO RECEIVERS The amateur often decides to add to his amplifying system either H.F. or L.F. units, and although this is not a difficult matter there is one point which must be watched unless disaster is to occur. Unfortunately there is still lack of uniformity in the battery connections of various receivers and amplifiers, and where an amplifier is to be added to an existing set, and is to utilise .the same batteries, trouble may arise. In some receivers the negative H.T. lead is joined to the negative L.T., and in others to the positive L.T. If it so happens that the receiver and amplifier have opposite connections, the result of connecting them up to the same batteries is to short-circuit the L.T. battery, since in one set the H.T. negative is connected to the L.T. positive and in the other to the L.T. negative. Hence it is necessary for the constructor to verify that in both cases the battery connections are the same. If they are not the same, the difficulty my be avoided by leaving off the H.T. negative connection from the amplifier. This will not affect its w-orking may be avoided by leaving off the H.T. negative is already connected in the receiver, and any damage to the batteries is avoided. When the amplifier is used with a crystal set or with its own batteries, the H.T. negative connection must be made as usual. ACOUSTICS EFFECTS OF FURNITURE The quality of reproduction from any loud-speaker depends, to a considerable extent, on the room in which it is used and also on its place in the room and even on the furnishings of the room. A similar effect is obtained with a piano in a room. When the furnishings and hangings are all removed and the piano is again played the result is quite different and the difference is emphasised as the loudness of the playing is increased. The jumbled result of the music in the empty room was not present in the furnished room, because of the absorption of the sound waves by the furniture, causing the sounds to die out quickly and not be prolonged so as to interfere with later sounds. This absorption is known as damping, and on the degree of damping in a room depends the clarity of the reception. In this respect it is obvious that the same speaker will behave quite differently in different rooms, so, in choosing a speaker, try it where it is to be used most, and try different types until the one most suited to the acoustic properties of the room is obtained