Wireless Broadcast

Star (Christchurch), Issue 17525, 30 April 1925, Page 4

Wireless Broadcast

CONTRIBUTED BY

"AERIAL.”

PROGRESS IN HIGH FREQUENCY COMM U NICATION. About a year or so ago there appeared in this column the story of the first trans-Atlantic two-way amateur radio communication. Many radioists will remember that amateurs for months had been vainly endeavouring to work their overseas fellow-amateurs. It was not until some genius suggested I that tests on very short wave-lengths J would prove successful that anything l very satisfactory was accomplished, j This short wave suggestion attracted j the attention of an American amateur i named John Reinartz, who is now world-famous, and still an amateur. This young man gave the problem his attention, and in a surprisingly short rime ho had evolved some very practical circuits, or rather, had modified some existing circuits, so that wireless in the region of 100 metres became ivt once a very pronounced success. I should have mentioned that John Reinartz is the inventor of tlie famous . Reinartz Tuner,” which has been a great favourite among amateurs during the last three and a half years. It was this tuner that first made him famous, and ever since that time be has been the leader in amateur radio ! in IT.S.A. Much has been said and written i lately about short wave eommumca--3 cion, but little “ inside dope ” has come to light. However, " QG'x ” for March and “ Radio News ” iur April tell it very interesting story of highfrequency transmissions. ior the past year Mr Reinartz, whose call signs are IQi*— IXAM, lias been investigating still further into the problems confronting successful short-wave work. During this time Mr Reinartz has been co-operating with XKF, the radio station at the Naval Research Laboratory i ll Bellevue, and together, with the help of several other amateur stations, lias been highly successful in elucidating some baffling mysteries. “ Why,” for instance, “ could signals from IXAM be heard easily at 1000 miles in day- | ■ light, and yet be totally inaudible at a distance of only 400 miles? Why did th<* stations engaged in the tests find that waves below about forty metres were not nearly as good as the eighty metre wave for signalling after dark, and why was the reverse true in day- 1 light?” Such questions as these, and a host of others, all had to be answered correctly before the work was finished. The story of how it was done is very interesting indeed. It is too long, however. go print, here in detail At

first cloud formations were blamed for the peculiar things that happened, but it was found later that the clouds had little or nothing to do with it. and that the sun was almost entirely to blame. For a long time it has been known to* radio engineers the world over that the sun has the power to ionize our atmosphere, and it has always been, held that this is th* reason that u ireless signals travel much better at night than in the davtime. J.he average one and a half kilowatt spark set as usually supplied to ships 7 ol “I'O'.t ->0 to 400 miles. Yet at night, the same set. as a rule, can easily cover a distance or 1000 to 1.500 miles. This snows what a difference to wireless Rl f :eS partly S ih Bnt the sun -weets short waves by reflection. Quoting Mr Reinartz:- “Marconi in his work had pointed out that verv short waves, less than one metre, could be reflected at will by the use of « proper reflector, and at present is doing it on longer waves. This reflection is man-made*. J ~ our short wave tests we were troubled with reflection also, but it was duo to the sun’s influence and could ho put to -i useful service. 1 told you how the twenty-one metre signals could he found at one distance, hut not at a shorter distance. It must be that the short waves are propagated into our higher atmosphere and upon reaching u given height. are reflected from a layer of our atmosphere back to earth Hie radius which they arc initially reflected is that place inside of the circle oi which the signal is „ minus quantity, and outside of which it can be found. The reason for this is the capability of the sun to ’onize our atmosphere. The depth to which this ionization Is possible depends on -die position of the sun w/tli Aspect to any position on earth, chan.-in- with every position of the son during twenty-four hours with respect *■> transmitting station locate,l ...t" one place. As the sun goes farther west a station that is in its - ionization range has to use a longer and longer ■wave to maintain contact with « given station, say, 300 miles away.As well as investigating all the forcexpericnced with the actual apparatus. Gear that was quite all rigid , ivns no good always on GO metres, wbil<* Airwaves below 40 metres som.* brand new circuits were evolved. 'I he final circuit was one which gave ; uml re- } suits; without “murdering” the I rams-

mitting valves, and which could be safely used with fairly high power. Some circuits were so- useless on short waves that hysteresis losses in the glass supporting the tube grid mounting would make the glass conductive and spoil or “ufurder” the tube. AMONG THE AMATEURS. Many well-known Australasian amateurs are following in the footsteps of Reinartz, and are busy experimenting on 40 and 20 metres. The writer has heard Z4AG, Z3AL, Z2AE on 4.0 metres, and the first named station was actually exchanging messages with ICMP who is located near New York. This work was done at night time when waves below 45 metres are supposed to have less carrj*ng power than longer waves at night time. Also the writer If as heard Australian 2DS on 40 metres at night, and last Saturday I heard Australian SM3K in daylight on the same and his signals were easily as strong as his h‘3 metre night-time signals. Last week some information was published about the forthcoming tests on 120-140 metres l>e tween New Zealand and Australia. T promised to publish the full New Zealand details before the tests, but tin unforseen event prevents this. Each New Zealand si a- ! fion lias been given a code word to | transmit, ai** 1 . it would hardly be fair I to publish the code words. '1 ho gc-n- j era! rules, however, are th- same av . the Australian ones given last- week. New Zealand stations will transmit early in tlie evening, that between ! 8 and 10 p.m.. and Australians wiil send between 11.30 p.m. and 1.30 ! a.m. New Zealand time. 'Those who j wish to listen in and report max send i 1 t vie it* logs to Mr R. G /back, * j Z2ISX. 22. Stafford .Street, ten. NEW ADPA RALLS. A local amateur has shown me bis •> latest tuner. ft is of the low-loss j| irari ty, and is a pretty little iustru- j' nvent. An untuned primary j. part ' , of the unit, and the colliding is so ' arranged that it may be set right, and then left. The tickler moves through an angle of 90 degrees, for a dial movement of ISO degrees, giving nice fine adjustment. The coils are wound with green silk covered wire on a skeleton bakelite frame, to reduce dielectric losses. This tuner is made in cither the “amateur wave” or “broadcast wave” and is known as the B-T tuner, made by the makers of the low-loss liremer-Tul!y eondenser. Another handy little “gadget” that some dealers arc now handling is a “safety-first wander-ping.” This plug contains a high resistance which will I pass enough current from the B battery for the plate circuit, but will not pass enough current to damage a valve filament if a wrong connection should be accidently made. It is a cheap plug, and .vhould save many times ics cost in valves.