RADIO WORLD.

Timaru Herald, Volume CXXIII, 7 April 1927, Page 13

RADIO WORLD.

“By Listener In.”

UNDERGROUND ANTENNA,

The trouble is that we know practically nothing of the radio waves which we impel into space to-day. We do not even know how the wares are propagated, whether the greater part of them goes through our atmosphere, or whether the greater part goes through the earth. It is not known what happens to the waves after they leave the radio -broadcast station and before they strike the receiver aerial. We know that something happens; hut our ideas as to just what does occur are mostly vague, and one guess seems to he as good ns another. In the meanwhile, avo knorv Ave are progressing slowly, hut surely, and the time Avill come, Avitliin the next ten years, Avhen interference between radio broadcast stations AA'ill he an inconA'enience of the past to marvel at, and read of only in antiquated and obsolete text hooks. Right now one of the most interesting possibilities seems to he underground broadcasting. Dr. J. Harris Rogers, of underground radio fame, has done a great deal along these lines, and it is a belief that much more efficiency can he had by burying the broadcasting antenna underground. During the next few months statiou WRNY avill test this theory, whether underground broadcasting is feasible, from its neAV transmitter at Coytesvillc, N.J., Avhere preparations are being made to make underground broadcasting possible. THE “ N ” CIRCUIT. At last Ave have some definite news of the “N” circuit of Sir Oliver Lodge. Details of this “mystery circuit have been held back pending patent and other matters being finalised. The Avell known British weekly, “Popular Wireless,” lias the exclusive rights to publish full descriptions, and readers will find the description of the first successful experimental set in the issue for September 18th. The way m which the set functions is not quite understood. It is considered that static is not nearly so troublesome, nnd that it is practically non-radiating. The tAVO-valve receiver, Avliich is fully illustrated, consists of a detector and one note magnifier. Between the aerial side ot the aperiodic aerial inductance and the grid is, first, a fixed condenser, then, the tuning coils shunted by a tuning condenser, and then a variable grid leak Avliich goes to the A battery negative. The lead from tlio plate goes through the audio transformer and also lias a shunt path to -the earth side of the aerial coil. No bye-pass is used across the transformer, and it is stated that practically only ono type, namely, the Silvcrtoivn, is of any use, and that success Avill not be likely to be reaped with another make. It is quite possible that the reason that the above low frequency transformer is necessary is because its self-capacity is low and does not allow the high frequency oscillations to take. the wrong path. It would be interesting to try other makes of transformers and interpose an H.F. choko on the anode side of the audio primary. One cannot help tlio conviction that this would function quite Avell. Great stress is placed upon the lay-out of the parts, and particularly of the wiring. Reaction is controlled by judicicais use of the filament rheostat, after the grid leak has been properly adjusted. The tuning condenser has only. three plates, and the inductance coil is correspondingly higher in value to compensate for the low amount of capacity used. As plug* in coils, presumably of low self-capacity, are used, both. for the aerial as Avell as tlio tuning coil, it is an easy matter to cover the full broadcast band, Avliich could not be done with a fixed inductance in the grid circuit. In the average receiving set, the condenser has a capacity between 250 and 500 micro-microfarads, and this coA r ers approximately 200 to 500 meters. The throe-plate condenser Avould not cover the same band. Will readers who are specially interested in the “N” circuit, and avlio try qut this noiv device. kindly report results, especially noting whether static is less troublesome. This can be done only by switching over to another set.

NOTES AND NEWS. A correspondent from the north is very appreciative of the notes appearing in the “Herald.” I must thank him for his very candid criticism. He has premised to forward his log book, which will be highly interesting. I wonder how many amateurs in Tirnaru keep a log book? Yon all should have such a hook to keep a list of stations received, weather conditions, and experiments made. | During the past week we have had i seme very fine receptions, particularly | from the Australian stations. | The modulation from 3YA has greatly | improved. IYA is as good as ever. 1 4YA is quite good at intervals. I 2BL is still the best station heard lin New Zealand. The modulation and 1 volume leave nothing to be desired. I You will notice that this station is | very consistent in this respect. The j concert from the Renown on 28th I March was exceptionally clear and | loud. Once again 2BL is to be congratulated on the broadcast from the Jenolan Caves on Thursday, Friday 1 and Saturday. It is about twelve months since this was last done. 2EC has been very busv with the Royal party. The reception in the 'Town Hall was fair: continual roar was duo to the very largo, crowd talking. The opera from His Majesty’s Theatre was patchy, but very enjoyable for all that. 2FC is a very fine station, but has not improved by coming down in its wavelength. 3LO has particularly good modulation, but is not consistent with its volume. 4QG is a very fine station, and puts on some very excellent programmes. 2BD, SCL, and 3A R are fair. The Pacific Coast stations in America are easily tuned in, and the clarity good. Have you renewed your license yet? On taking out, my Ircense I was surprised to learn that I had to make another declaration of secrecy. Fiveyears ago we did this, and you would think that this was sufficient, but the Telegraph Department thinks otherwise.

1 wonder if the 8.8. C. will publish a balance sheet for the past twelve months?

. 2YA Wellington is nearing completion. This station will bo ten times the newer of 3YA. It_is years since wo had good transmissions from the “Windy City,” and Jet’s hope we are In for a treat in the future. I will he pleased if amateurs will and let me know how they receive 2GB;