http://elecraft.85.s1.nabble.com/K4-S-meter-characteristics-tp7660056p7660077.html
controls, hear the station, work him, move on. I dont need a fancy dbm or
worked the guy. When you contest, who the hell cares, hear him, work him,
move on. In simple terms, I just want selectivity, and no agc pumping and
radio. Love my K3S, great radio. Simple to operate once you learn its
> Now that the K4 has exact knowledge of its gains and losses through the
> preamps, attenuators, splitters, bandpass filters and so forth, could this
> enable an alternate way of visualizing the receiver's range? This alternate
> measurement would be quite useful in setting the controls optimally for any
> situation.
>
> Imagine a scale -- I suppose it would be in dBm -- showing the K4's total
> dynamic range. Say it's 100 dB in total. The lowest point is the minimum
> discernable signal (MDS); the highest point is the damage level, or if
> that's a bit too frightening, call it the maximum ADC level or something
> else to denote it as a Level Not To Be Exceeded.
>
> Since the K4 will know not only what the noise floor of the band you're
> listening to is, but the absolute value of that level in dBm, the scale can
> be annotated with a dynamic marker to show where the band noise falls in
> that 100 dB range. I'm calling it 'dynamic' because it'll vary a few dB as
> band noise does, but it will sit at a calibrated level, relatively
> motionless on the scale as Wayne described the S-meter doing.
>
> As the operator kicks in more gain by turning on preamps or turning up the
> RF Gain, the scale shifts downward by the same amount. For instance, if the
> scale was showing -120 to -20 dBm -- a 100 dB range -- and then the
> operator turns on a 10 dB preamp, the scale must change to -130 to -30 dBm,
> because the preamp has made the receiver more sensitive while also reducing
> the max permissible level.
>
> Conversely, if the operator turned on 10 dB of attenuation, then the scale
> would shift upward to -110 to -10 dBm, indicating clearly that sensitivity
> is being sacrificed for greater large signal handling capability. The noise
> floor, being a relative constant, would move closer to the bottom of the
> window, or rather, the window would move relative to the noise floor in
> such a way as to place it 10 dB closer to the bottom end.
>
> So actually, as I'm thinking about this, the meter wouldn't move at all.
> It's the noise marker that would float higher and lower within the window
> as you varied the controls, just as on an S-meter. I guess what I'm
> describing here is more or less an S-meter calibrated in dBm!
>
> But perhaps the best reason for looking at the receiver this way would be
> to tune the controls precisely for a given noise floor. Twenty meters, with
> its -120 dBm noise floor, will require one combination of preamps and/or
> attenuators. On 80 meters, if the noise is, say, -100 dBm, the operator
> knows (because he can see the graphic) exactly how much attenuation is
> acceptable while still keeping the band noise marker in the operating
> range. It would behoove the operator to keep the noise floor marker near
> the bottom to 1) give him the maximum dynamic range under those conditions,
> and 2) to avoid becoming "my K4 is noisy" guy.
>
> Presumably, as each K4 goes through RF calibration at the factory it will
> know exactly the gain of each preamp, attenuator, filter, and splitter in
> its path. The scale could be custom for each individual unit, although I
> wouldn't want to start any "my K4 is more sensitive than yours" wars.
>
> I leave it to the programmers to decide on the specific eye candy of such
> a readout. I for one would find this type of meter fun and useful in
> getting a mental picture of where in dynamic range space the receiver is
> sitting.
>
> Can anybody see any flaws in this idea? I can foresee at least one. I
> don't know how the front end of the K4 will work, but if it is constantly
> moving the receiver range in response to what it hears, that is, in
> response to the total amount of power incident on its antenna port, then
> perhaps that might pose a real challenge to giving this type of feedback to
> the user. I don't know.
>
> Al W6LX
>
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