I'll take a stab at trying to explain how the s-meter works.
Now the K3 may do it differently since it may be done by the DSP, but in normal analog radios, the IF is tapped at some point and goes to a noise amplifier and detector. This produces a varying dc signal that is used by the AGC circuit to control either RF gain or IF gain or both depending on the design. Usually the s-meter reads this varying dc level. RF gain allow the operator to shift AGC by adding a dc bias up or down, thus it should affect receiver gain. lowering RF gain lowers both noise and signal which may permit the receiver to operate at a better level for extracting the signal (i.e it sounds quieter). But by varying the AGC level the s-meter is fed a constant dc bias as well (typically the s-meter rises). In some designs the noise amplifier also drives the NB. So saying the s-meter is showing the level that would be needed to be heard is a little wrong. S-meter readings with RF gain reduced are just not calibrated and thus of little use. To divorce the s-meter from AGC takes more circuitry and it sounds like the K3 has that ability by use of the ABS mode (I leave it to the K3 experts to explain this if they desire). Loudness of audio and strength of signal are not the same, usually. In SSB there is a more direct connection as there is no carrier transmitted. In FM often audio can be set too low (low deviation) and still see a S9+++++ signal. Data mode don't usually speak in terms of loudness (unless your brain can decode FSK or PSK signals - little joke!). In general loudness is a function of modulation and not signal strength. But obviously this is a gross generalization and not very exact. 73, Ed - KL7UW ------------------------------ Message: 30 Date: Thu, 15 Jul 2010 09:49:27 -0400 From: drewko <[hidden email]> Subject: Re: [Elecraft] K3 S Meter behavior To: The Smiths <[hidden email]> Cc: [hidden email] Message-ID: <[hidden email]> Content-Type: text/plain; charset=us-ascii The way I understand it, turning donw the RF Gain does not "improve" the signal's s-meter strength. The increasing level of the s-meter as you reduce the RF Gain indicates the level that a signal would need to attain in order to be heard. For example, if you turn the RF Gain to 12 o'clock you will only be able to detect signals that are approx S9+30db or greater. Personally, I would prefer that the s-meter not operate in this way in ABS mode. RF Gain should have no effect on the s-meter action when in ABS mode, just as ATT and PRE do not. 73, Drew AF2Z 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-QRT*, 432-100w, 1296-QRT*, 3400-fall 2010 DUBUS Magazine USA Rep [hidden email] ====================================== *temp ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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