I have done the same thing to calibrate my vfo's. But remember, when you are right on frequency, there is nothing to indicate that there is another signal there. And, I'll be honest, I've never seen my s-meter add the two signals together which would indicate that the powers are being added in the receiver. I have had to reduce the vfo signal to keep it from overriding WWV which is kind of my point. In fact, I just did this using my RF generator. WWV at 5 Mhz is about 10 over S9. The generator is at about S5 with no antenna connected and the lead just resting on top of the transceiver. When I switch the generator on, the S-meter moves not a bit. You would expect it to jump considerably if the RF signals were being added together.
Jim WA0LYK --- In digitalradio@yahoogroups.com, "Jose A. Amador" <[EMAIL PROTECTED]> wrote: > > jgorman01 wrote: > > > I may be wrong but I beleive your theory doesn't assume that the RF > > energy at your reciever's antenna is not additive. In other words, > > the signal from the transmitter you want to hear and the interfering > > signal do not add together. > > Do you mean that superposition theorem does not apply? You are wrong, Jim. > > > You can only discern the strongest signal. > > In psychoacoustics, that's called "masking", if both signals are close, > but on different frequencies. > > > An example is, that if you put a carrier on the air and I > > receive it at S9 and then someone else puts a carrier on the exact > > same frequency but it only arrives at S8, I'll never know it is > > there. > > It is not the case. Two coherent signals, one 6 dB weaker than the other, > when added up give rise to a signal 0.972 dB stronger than the stronger > one. You may not perceive it, but it does not deny the superposition > theorem. > > I doubt they can add up coherently from two separate VFO's (unless you > have two > GPS locked DDS's) ...you would get a very low frequency beat, and if > it is below > 20 Hz (or your audio's low frequency cutoff), you will see the S meter > dancing, > and hear nothing at all. > > I used to calibrate my crystal calibrators that way. > > > Therefore, when you remove the interfering signal, you also remove > > any possibility of retreiving information from the signal you want to > > hear. > > ??? > > > Consequently, you will never have a coherent signal to decode. > > It will always have missing information. > > What information does an umodulated carrier carry ? > > > Any other assumption means noise, especially random noise, would not > > be a problem, and that you could always subtract a signal from it. > > Every mode I know of, digital or analog, has a minimum signal to > > noise ratio that is required to decode it. > > Analog signals do not need to be decoded, are they just perceived. > Maybe you can specify a certain minimum SNR for comfort, that's all. > > > Jim WA0LYK > > > > __________________________________________ > > XIII Convención Científica de Ingeniería y Arquitectura > 28/noviembre al 1/diciembre de 2006 > Cujae, Ciudad de la Habana, Cuba > http://www.cujae.edu.cu/eventos/convencion > Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
