WIRELESS NEWS.

Press, Volume LIX, Issue 17863, 8 September 1923, Page 11

WIRELESS NEWS.

ACTION OF A RECEIVING VALVE. RECEPTION OF AMERICAN AMATEURS. (shccuix* warms tob "thh fbxss."} (By "E!ectra.") When the filament in a valve is heated nnd tho grid and plate are disconnected, negative electrons are given off from the filament, but on account of their small velocity they do not move far from the surface of the filament, and i n fact they return to the positive end of the filament. When tho plate of tho valve is connected with, the positive end of the filament, tho plate, of course has a slightly positive potential with respect to ' the negative end of the filament, and the electrons, which after all are negative electricity, aro attracted to the positive plate, and they flow in the external circuit between the plate and the positive end of the filament. The number of electrons which reach the plate is small. When a positive potential is supplied to the plate, a far larger number of electrons are passed to the plate, until a point is reached at which no more electrons are drawn to the plate by tho addition of positive volts. If now a small potential is supplied to the grid, tha grid will influence the number of electrons, which go to tho plate. The grid of course is much closer to tho filament than the plate, and is made of fiue wire with large spaces in between tho wires. If a small positive potential is supplied to tho grid a large number of electrons will be attracted to the grid, and some will actually flow in the grid circuit, but on account of the spaces, a large numbor wdl pass through tho grid openings and will reach the plate, so. that we have two currents, a small grid current and a much larger plate current. If now a negative Dotential is applied to the gridj the grid returns the electrons back to the filament, and but few are able to escape through the openings and reach the plate.' When n varying potential is applied to the grid, a varying number of electrons pass through the openings of the grid to the anode. Actually the .shape of the current curve in the plate circuit is identical with the voltage curve applied on the grid. AN ASHBURTON LOG.

SUNDAY, AUGUST 26th, 1923: 7.7 p.m.-4AA de 3AB. 7.14 p.m.—9l3JK. 7.24 p.m.—6ARB. 7.31 n.m.—6AWA Siga. QSA. 7.34 p.m.—SGOF do SBOU; 7.41 p.m.-6CBU de 9ZT. 7.46 p.m.—2AY. 7.47 p.m.—6CK de OZT. 7.49 p.m.—s 9ZT. 7.50 p.m.—Msg ending—ipse letter 735.' 7.51 p.m.—6CBU de 9ZT. • 8.0 p.m.—Msg to 6CK from 9ZT. 8.15 p.m.—6OLD de 6ARB, got whole msg. OK. 8.38 p.m.—CQ de 6AWA" Bigs. QSA. 8.40 p.m.—9BRU de 9ZT, K. 8.4<2 p.m.—CQ de 9ZT.. Siga. OSA. 8.59 p.m.—9ZT de 6ZR. 9.K) p.m.—7AGV de. S.IS p.m.—GAS de 9AX.B. 5.22 p.m.—OK 9ZT ar. 9.30 p.m.—4AA de 3AB. H W.-M. DAWSON. ' This is a very good " 'catch" indeed for a one valve standard regenerative set, and Mr Dawson is to he eomphmented upon it. 9ZT, OAWA..-4ZT, and <3AB, were the west stations. TO DRILL A HOLE IN GLASS. To the amateur who would like to bring his aerial lead-in- wire through the centre, of the window-pane, instead of via the less efficient lead in tube, the following hints on the drilling of glass may be of use. ' ' 1. Give firm support to the„£lass opposite the part to bo drilled; a flat oiece of wood with two or three, thicknesses of_ newspaper on top is as good as anything for this. 2. For .the cutting tool use a dia-mond-pointed bit of Rood-qiwlity steel which lias been made ,g las f h F d „. 0 ?f quenching from a red heat in. wellboikd salt water. -. 3. Use a good; high-speed breast-diill, or an Archimedean drill, for revolving tho bit; kee» uo' a good speed, but do not use much pressure on the work. 4 The drill should bo guided- at first bv means of a strip of hard wood drilled with a hole the saaia size as the bit The guide should preferably be clamped m 5 Lubricate continuously with 'turpentine in which one or two pieces of champhor have been dissolved. . 0. Drill half-way through from each side of the glass. In conclusion, to enlarge or true-up the hole use a small, sharp, round iile, well lubricated with the • turpentinecamphor mixture mentioned above. ~ CORRESPONDENCE. ' LB- RICCARTON, requires the dimensions of a .006 mfds. fixed condenser," and also if Indian ink is suitable for a grid leak. .. .. , . .Seven plates 14 by \\ inches separated by mica .003 inches thick, lour plates forming one e,ide of the condenser and three the other side the whole to be clamped firmly together. The'sample--piece of mica you iorwarded will be suitable for the above. The mica sheets should be J-inch bigger than the plates on all sides. Indian ink is quite suitable for srid5 rid leaks. ' .F., LINWOOD, asks: "Do the new li-volt valves work as well as the 6-volt typo, and are they obtainable in Cnristchurch; also, what type of circuit gives the best lesults with this valve?" The valve in question certainly works as well, and in many cases better than, the ordinary type, and they can be used in any circuit in wliich the 6-volt type is used. See article in "New Zealand' Wireless and Broadcasting News," August • 20th, rj'23. r , At present there are none of these valves lor sale in Christchurch, though some will bo arriving shortly. They are procurable in Wellington at the present time. G.G., WAIHAO DOWNS, requests a copy of the non-regenerative, fcinglevalve circuit lately invented by l>r. Franklin Satterkc, ' and asks where peanut tubes can beobtaincd. I will try and obtain data on this ! circuit, thuiigh up to the present time I have not heard or read anything in connexion with it. .A Wellington firm, I believe, have p&inut tube»in stock at 50.s each. ; 'HOT SHOT," WAIMATE, asks: (1) for tlve number of turns for H.O. coils and spider-web coils forthe concert wave-lengths using an aerial of 197 metres. (2) Would a circuit using one stage of radio frequency and feed-buck from the plate of detector tube on to the primarv' and secondary came interference? (3JI If 2, 3, or 4 stages of audio woidd be ellicient for reception of conoerts? Try 25 turns in primary, 35 in secondary, and 50 in tickler, and .with a usual size tuning-condenser ypu should be able to get in most of the broadcast and amateur transmis- i sions. Th© spider-web coils will need about the same number of turns with the first winding 2 inches in . diameter (same as H.C. coils). (2). It will depend upon how the circuit

is used in the matter of interference Proriding you use a ieasc**bto loose-coupling between the tickler and secondary, and stop the set lating as soon as you get on to telephony, and make a of always bearing in mind the above two facta, you will be quite O.K. <S) I would not advise anyone to use more than two 6tages of audio-frequency when receiving radio concerts. If more than that number are used, bad distortion will take place. I am doubtful of the number of values you intend using in the circuit you ask for. Please let a>»

know if it is 3 or 4. H. 5.8., UMARU, wants to knoir.-(l> If a 8-cod, single value circuit will receive all New Zealand broadcasting; (2) which is the best for detector purposes—a French R. or a Marconi V 3* type valve; <S) if a rheostat of 1 amp current capacity is or 14. amps; (4> what are the regulations concexning regeneration. (1) The circuit you mention would not be capable of receiving the distance required. You would need two or three valves at the least. <2> . Both the valves are primarily amplifying ones, and there is not a great deal of difference between them as detectors. (3) The 1-amp rheostat would bo quite sufficient. (4> FoW , lowing is rule 66 of tho Government regulations: "In the interests of radio telegraphy generally, the types of receiving circuits authorised by tho license shall not include those which, in tho judgment of the Minister, unduly energised tho receivina antenna. Note.—An example <w such types is that in which one coil of a two-coil tuner is used as a reaction coil, inductively coupled to the antenna coil."

The standard regenerative tets using plate and grid variometers, or only the latter ore allowable. Tbe two main circuits that are barred are those using a single coil tuner, and the well-known tickler circuit.

L.8., RICCARTON (second letter), wishes to know the capacity of two variable condensers, one with 15 movable and 16 fixed plates, and the other with 11 movablo and 12 fixed plates, in both cases spaced |-incb. apart. The capacity of the former is 001, and the latter .0005.