jgorman01 wrote: > 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
With such a large ratio (34 dB based on 6 dB per S unit) you won't be able to PERCEIVE anything. But theory, nevertheless, applies. S meters are logarithmic indicators, precisely because they have a too wide ratio of signal strenghts to display, say, ideally 94 dB from S0 to S9+ 40 dB, a 2511886431 (two and a half billon times) power ratio Being practical, it is really hard to discern a 1/100th movement on the needle, a 40 dB ratio, being the S meter movement (a D'Arsonval coil or a mimic of it) a linear responding, VOLTAGE sensitive device. To really perceive something, the power ratios have to be much smaller. A logarithmic indicator COMPRESSES the differences. A linear indicator would show a larger response, but would have a much smaller dynamic range. Also, it depends on the S meter dynamics. With a fast attack, slow release AGC loop you will not see any pumping, as the syllabic period of speech on SSB is longer, and the peak holding AGC dynamics will hide any low frequency beats. It takes an old style, AM AGC loop to see any pumping, and a rather small small signals ratio (almost equal signals) to show it. Finally, Dr. McGwier gave a reply on something about the radio characteristics, advancing that future SDR designs should somehow be able to combat BPL QRM. State of the art, conventional radios are nothing else than a more or less expensive black box in the digital communications chain. Of course, it has to have some minimum performance specs, or the chain will break. SDR's should bring some new tricks to our boxes, as they are the only ones really capable to do so, while performing at least equally to hardware defined boxes. Jose, CO2JA __________________________________________ 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/
