Satgen 417 More Signals in Noise by GM4IHJ (BID SGEN417) 22 Mar 97 Yamaha Effect. The IHJ residence is in the middle of a quiet Scottish village, where, apart from one or two computer games machines , the radio spectrum is relatively clear of QRM. Except that is at 0715 and 1815 local, when a neighbour leaves for, and returns from work, on his motor bike. Over several years it has become obvious that a particular coincidence , is no coincidence at all. As he passes , satellite signals previously inaudible in background noise, suddenly come through . Their clear tone very evident against the ignition noise of the motor bike. Once he has gone, so have the satellite signals. This is not a new phenomenon. There have been reports in the past from both Moonbouncers and satellite users, but up till now no direct scientific evidence has come to the notice of this author. Now the UK science magazine NATURE Vol 285 for 23 Jan 1997 has a review article on page 291 and a paper on the subject on pages 319 to 321. The title of the paper is "Stochastic Resonance in Non Dynamic Systems without Response Thresholds ". So ordinary folks like us can be excused if at first we do not appreciate its relevance to satellite or EME operating ( or submarine passive sonar operating and other weak signal work where the phenomenon is not unknown). In principle the paper suggests that all we need is our weak received signal, plus an additional source of noise. You can use white noise from another receiver, but experience at IHJ suggests a sequence of randomly generated pulses is optimum. The pulses act as a threshold triggering device , and when signal plus noise exceeds the threshold , the system responds momentarily making the signal audible. Then it relaxes until the next triggering pulse. In practise the signal to noise seems to rise as the level of introduced pulse noise increases. A feature which the loud IHJ motor bike noise demonstrates perfectly, as the bike approaches and passes the shack altering speed as it does so. Needless to say IHJ has no intention of ever complaining to his excellent neighbour about this. Please note that the NATURE paper quoted above, is not for the mathematically faint hearted. Nor is it aimed at radio operators. The authors are more concerned with signal effects of this type in physico-chemical systems, such as semiconductor p-n junctions; mesoscopic electronic devices; voltage dependent ion channels and the like. But those are the authors fields of interest. This phenomenon clearly applies to weak signals in radio communications , as has been recognised for years by several satellite and EME operators. What the paper does do however is that it puts the subject in its proper scientific and mathematical context. The review article mentioned above is much easier reading than the Bezrukov Vodyanoy paper. For those interested in a good amateur radio review of signal in noise topics, the recent discussions on MOON-NET@VM.STLAWU.EDU cover a lot of useful ground in respect of operator hints and tips for weak signal operating.