There is also the 'propagation beyong cutoff' phenomenon that you could be experiencing - the same reason why AM radio stations 'die' underneath bridges and overpasses and why a hand-held AM portable radio signal dies off when taken inside a car ... this is due to the wavelength of the radio signal being MANY time the opening of the aperture comprised of the bridge and thereby NOT conducive to effective propagation. This is especially noted when working with waveguide at microwave frequencies - where waveguide has a definite _lower_ frequency of operation below which attenuation climbs rapidly ... extrapolating to open/free space it can be seen that AM Broadcast signals would be subject to similar effects - with the problem is only worsening at 60 KHz ... With this in mind - are all these clocks in the same location? Jim ----- Original Message ----- From: "Lawrence Lile" To: Sent: Friday, May 24, 2002 9:02 AM Subject: [EE]: Sensitivity training for Engineers > How do people go about testing sensitivity of radio recievers? I've got a > batch of clocks that recieve a time code over WWV, and some of them "seem" > to be less sensitive than others. Some nights I'll see 5 out of 5 lock onto > the WWV signal, other nights only 1 out of 5. I don't have any calibrated, > predictable way of saying "Yes, this reciever is sensitive enough". Niether > me nor my supplier has a good way to do this. > > I am imagining a transmitter, suitably armored in a really good faraday cage > to prevent problems with the FCC, that I can turn way, way down in a > measurable way, and test whether the reciever modules can pick up the > signal. I think this would be quite difficult to build. A transmitter that > fakes a WWV signal and transmits 100 mW would be trivial to build, but how > about one that only transmits 0.01 microwatt? I could see building the > transmitter in a separate can, moving the 100mW signal through a coax to an > attenuator, then through another coax into another can holding my product. > > What is actually a reasonable level of power that a reciever in the US might > get from a transimtter in Colorado? It must be vanishingly small. > > Hmmmm..... > > > -- Lawrence Lile > Sr. Project Engineer > Salton inc. Toastmaster Div. > 573-446-5661 Voice > 573-446-5676 Fax > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.