[Elecraft] K3 Rf gain tracking (main vs. sub)

[Joe Subich, W4TV]

 > Contrary to my earlier statement my K3's main RX does show an RF gain
 > non-linearity.

I certainly don't see any non-linearity here in either the K3 or KRX3.
Using your "angle" references (RG/RG$ are the RF Gain values reported
by the CAT protocol):

         --- MAIN ------       ---- KRX3 ------
         RG;  ADC   dBV        RG$;   ADC   dBV
   CW    250  239      0       250    239      0
    0    228  210  - 0.5       231    213  - 0.1
   45    182  164  - 4.2       181    169  - 4.2
   90    130  114  -16         132    124  -17
  135     90   77  -34          91     86  -35
  180     47   46  -51          50     49  -51
  CCW      0   02  -85           0     02  -85

The compression at the "top end" is expected since the -73 dBm signal
is well above the AGC threshold until the RF/IF gain is reduced to
about the 12:00 (90 degree) position.

K3 s/n 1450 firmware 4.14, DSP 2.60.  Both receivers are calibrated
using the XG-2 on 20 meters with K3 Utility 1.1.10.15.

73,

    ... Joe, W4TV


On 10/26/2010 3:23 PM, hb9brj wrote:
>
> After reading all comments, I performed an RF calibration using a -73dBm
> source and the K3 Utility 1.3.10.15. First run with factory defaults, second
> run using my signal source. A picture tells more than a lot of numbers:
> http://home.datacomm.ch/hb9brj/RFgain.jpg
>
> X axis = RF gain position angle in degrees: 0 = 3 o'clock, 90 = 12 o'clock,
> 180 = 9 o'clock
> Y_left = CONFIG:SW TEST SCN ADC readout of RF gain pot
> Y_right = DISP AFV in dBV
>
> Contrary to my earlier statement my K3's main RX does show an RF gain
> non-linearity.
>
> Markus
> 1505