[Elecraft] Regarding the K3 and high QRN levels

[Guy Olinger K2AV]

AGC is instant and dynamic, and does not vary RF gain, PRE/ATT settings
which are static unless the user changes them. RF gain, PRE, and ATT result
in numeric "advice" to the CPU, rather than being in direct control of a
circuit or device as in an analog receiver.  The CPU in turn drives the
actual circuit devices from it's many outputs.  There are many uses for this
indirect linking.

At issue is that the main smart AGC is digital signal processing, and is
*AFTER* the analog to digital conversion (ADC).  The RF gain (which is
really IF gain), PRE and ATT are before the ADC, and improperly setting
those can squeeze the noise into the high numerical range in the conversion
or even engage the defensive hardware AGC which is better off not being
engaged.  The defensive AGC is analog, has no smarts, and unfortunately must
reduce signal-to-noise in doing its job of preventing ADC input overload.

Those who understand how the rig works will throttle back the pre-digital
controls to where noise is at most moderately loud to obtain best operation
of digital features.

What I am suggesting is that in an "AUTO" novice mode a slow (rate of human
turning the RF gain) throttling back can be set (and then left alone) by the
radio for those who are not into the theory and do not recognize the source
of their complaints as being caused/worsened by their misadjustment of RF
gain, PRE and ATT.

Leaving PRE on and RF gain at max on all bands regardless causes the digital
AGC to increase or reduce the noise to the same level as the wanted signal
in pauses.  This reduces the effectiveness of the NR algorithms.

Those who ride their own RF gains would not be using this.

73, Guy.

On Fri, Jul 9, 2010 at 12:37 PM, Wes Stewart <n7ws at yahoo.com> wrote:

> That sounds amazingly like automatic gain control, something I thought you
> "ride the r-f gain control" types studiously avoided.
>
>
> --- On *Fri, 7/9/10, Guy Olinger K2AV <olinger at bellsouth.net>* wrote:
>
>
> Or, perhaps, sinisterly, simply make this happen in the firmware
> without telling anyone.
>
>
>