[Elecraft] K3 AGC dead spot

[Chuck Shefflette]

Guy,

Actually, the RF gain control does have an affect on the analog, as does the
AGC. There are 2 types of AGC in the K3, the first is the more obvious that
is controlled by the AGC Slow/Fast/Off and the second is a hardware AGC that
protects the A/D converters. The "normal" AGC is summed with the hardware
AGC to control the gain of the IF amplifier that immediately precedes the
2nd mixer stage. The "normal" AGC is also more than likely used in some of
the DSP calculations but that is a little less obvious to the outside
observer.

The Pre and Att controls, on the other hand, have real effects on the
electronics. The Pre is used to switch the PIN diodes that control the
signal path through our around the 11 dB RF Pre-amplifer stage. The Att
switches relay K10 which physically switches in and out a 10 dB attenuator
circuit.

Granted, all these controls result from switch presses (the Att/Pre) or the
A/D results of the RF gain pot that are decoded by the MCU and transmitted
to the appropriate control circuits, but they do really have an affect on
the radio's operation, not just in the software.

However, you are right when you say this isn't a traditional analog radio,
at least beyond the 2nd IF stage!

73,
Chuck, AA3CS
K3 #s 4072 & 4407


Guy, K2AV wrote:
> 
> The thing to note here, this ain't your daddy's analog radio, the only
> actual "stage gain" adjustments you have are ATT and PRE.  The rest is
> all in the numbers, as the front panel knobs are just numerical advice
> to the firmware.  They don't directly control anything.
> 
> ...
> 

-----
73 - Chuck, AA3CS
-- 
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