K2 Ser no. 3181

[Ron Lorenz]

Love this little rig. One slight (mini) probem. Based on over 50 years of
radio operating, amateur, commercial and military I always leave the RF gain
on max for best SNR.

With my K2, turning the control to any position, (max to min and back agin)
makes no difference in gain (Noise) except to shift the position of the S
meter reading, ie, iaw the HI and LO Cal procedure.

Any ideas?

73

Ron VA6RL

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Hello Ron,

Your AGC threshold has a huge effect on  the range of adjustment of the
RF gain control. If the AGC threshold is set too high - meaning that you
are generally operating with very little AGC action - your RF gain
control will have very little effect. If you lower your threshold,
you'll find that the RF gain control will have a much greater effect.

Just a reminder, R1 on the control board is what controls this
threshold, and in the K2 manual, the information relating to this
adjustment is located right next to the info about the S-meter
alignment. (page 46 in my Rev D manual for S/N 3039, so it's probably
the same version as yours).

Hope this helps.

73, Dale / WA8SRA

Ron Lorenz wrote:

>Love this little rig. One slight (mini) probem. Based on over 50 years of
>radio operating, amateur, commercial and military I always leave the RF gain
>on max for best SNR.
>
>With my K2, turning the control to any position, (max to min and back agin)
>makes no difference in gain (Noise) except to shift the position of the S
>meter reading, ie, iaw the HI and LO Cal procedure.
>
>Any ideas?
>
>73
>
>Ron VA6RL
>
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft   
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>Elecraft web page: http://www.elecraft.com
>
>
>  
>

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[Don Wilhelm-2]

Ron,

The 'RF Gain' in the K2 is actually an IF gain control and it only controls
the gain after the selective elements.  All the stages ahead of the IF
amplifier operate at fixed gain levels.

In many receivers where the RF stage is gain controlled, my experience is
that the gain can be made excessive and actually results in added noise when
it is advanced to maximum - this is contrary to your experience, but it goes
to show that the noise floor of any receiver is the result of careful design
for minimum noise.  The K2 is in the category of such careful design.

The K2 AGC works similarly - only the IF amplifier gain is changed with the
AGC.  The 'RF' Gain control changes the resistive network that sets the AGC
level - so the net result is that the RF Gain and the AGC interact to set
the IF amplifier gain.  You may wish to check the AGC threshold just to be
certain (although it does sound like it is set just fine).  Switching from
AGC on to AGC off should cause no increase in the noise level when listening
to a quiet band (local noise sources CAN produce broadband noise, so use a
band where such noise is at a minimum for your location).  If the AGC
Threshold is set in this manner, one can expect little or no change in the
K2 noise floor when the RF Gain control is rotated.

73,
Don W3FPR

----- Original Message -----

> Love this little rig. One slight (mini) probem. Based on over 50 years of
> radio operating, amateur, commercial and military I always leave the RF
gain
> on max for best SNR.
>
> With my K2, turning the control to any position, (max to min and back
agin)
> makes no difference in gain (Noise) except to shift the position of the S
> meter reading, ie, iaw the HI and LO Cal procedure.
>


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