RADIO NOTES

Manawatu Standard, Volume XLV, Issue 100, 28 March 1925, Page 12

RADIO NOTES

(]!y “Squealer.”) During the past week, Mr Johnson (2GA) lias seen operating on Morse and, although apparently no local amateurs have it ggeu him, nas successfully worked seveial Now Zealand stations. On Tuesday night using 3 watts input lie raised 4 1 L (Mr A. H. Grubb, 53 Sligo Terraci, Koslyn) who reported that his sigrals were clear. Mr Johnson has also 1 een in communication with 2BU, 2BX, aid 2AW. On low wavelengths, Mr Johnson has found considerable “fadi: g” wiien working South Island static ns and is experimenting further with the object of testing the theory that there is a ‘'silent area’ between the .wo islands. There may be some ground ; for the supposition as it is a reniarka >le tact that Auckland stations can be more easily heard than those in Wellington, which is, of course, much nearer this town. Perhaps in tho mountain raiges between here and Wellington t lere is a deposit of some mineral whii h affects the waves. In Wales such i “silent area” exists and music broadc ist from London cannot be heard there. Further experiments may throw some light oil this interesting problem. Tho local c ub license has at last come to hand and it is anticipated that the station will bo put into commission shortly. The call-sign is 2GI, and the wave lengths allotted are ICO, 170, and 180. The m iximum input is 15 watts but it is inti nded to work on 10 watts at first.

Most amati urs when starting on valve work imagine that any valve will work quite well so long as the filament lights up. But as t matter of fact good detectors are mrd to find, and should be treasured. It is almost axiomatic that soft vc Ives are better detectors than hard vi.lves, but this proposition needs some qualification (says a writer). For instance >n C.W. telegraphy a hard valve makes n excellent detector, since it is used ii an oscillating condition and the actii n is really not that of a detector at a 11. The signals are heard in the phon s by reason of the fact that the incoming oscillations and the local oscillat ons heterodyne one another and ca ise an audible beat note. The same be it occurs with two clocks ticking at v iry nearly blit not quite the same, sp sed. A valve used for heterodyning is not rectifying the oscillations in the same way as a valve used to detect sp :ech or spark signals. It should then fore be remembered that because a vt ive brings in C.W. notes with good sf -ength it does not follow that it will v irk equally well on music. Quite a nun oer of amateurs remark that they cai get a strong carrier wave but very poc r music, and while sometimes this is duo to a poor percentage of modulatio at the transmitting end, it is very of en due to the fact mentioned above that a valve is not necessarily a go d detector because it heterodynes stn ngly. Tho two functions are quite in- ependent of one another, although in practice they are easily confused. Ti o theory of the soft valve is as yet no properly understood but it is well sc itled that the soft valve gives tho be t results on faint music, it is certain y much more critical and requires ver accurate adjustment of filament curi int and plate voltage, but the results /arrant tho extra care needed. Wii h the introduction of dull emitter valve s the soft valve is tending to lose popu arity in England and the U.S.A., for he reason that the addition of a stage or high frequency amplification is qi ite cheap. Quite a number of American sets now use UVI99 or 0299 valv s for high frequency, detection, and low frequency stages. The reason is of course that very accurate control of tie valves is quite unnecessary and th 3 assists the tendency towards simplit cation which become greater every da; . In this country, however, where ;)X work is still essential, tho supersensitive detector valve will probably hoi i the field for some time. Most New Zi aland 1 amateurs cannot afford to empioy several high frequency valves to in: ke up tho deficiencies of their detecto s.