[Elecraft] [K3] RX Gain Calibration

[Don Wilhelm]

Travis,

I doubt the RX gain calibration will make that much difference, but 
rather I suggest that some alteration of the AGC parameters will make 
the most difference for you.  Take a look at the "Noisy K3" article on 
my website www.w3fpr.com for some guidance in adjusting your settings.   
That article was written before the AGC parameters were expanded, so you 
will have to experiment a bit, but the article should give you some 
guidance on which direction to go.

Turning the preamp off and even turning the attenuator on for lower 
bands where the band noise is higher will make a great difference too.  
If you can hear an increase in band noise when the antenna is connected, 
you have ample gain - turn off the preamp and try connecting the antenna 
again - if there is still a substantial increase, try turning on the 
attenuator.  You are not going to be able to copy signals below the 
noise level, so you don't need the added gain - it just makes everything 
(including the noise) sound louder.

73,
Don W3FPR

On 3/18/2013 8:24 AM, Travis Brown wrote:
> All,
>
>   I put together a K3 kit about 6 weeks ago. Wow, that was an amazing
> project.  Many thanks to Elecraft for making that option available.  The
> problem I am having is that on 180/80/75/40 and sometimes 20, the noise
> floor is about S7-9.  It is about the same on both my antennas (OCF dipole
> and 43' vertical) with the OCF being a smidge quieter.  My first thought
> was that I had some local noise and asked my dad to bring over is KX3 so I
> could walk around the house to find the source of the noise.  I did find
> that the power supply in the iMac is ridiculously noisy, but that wasn't
> getting into my signal, especially since my antennas are almost 100' from
> the house.  What I DID notice was that when I plugged my antennas into the
> KX3, the noise floor was at S0 on 20/40 and around S1 or S2 on 75/80/180
> with the pre-amp off.  That was MUCH better.  Of course, if I fiddle with
> the RX gain knob, I can make the noise go away, but it does mess with the
> S-Meter and it becomes increasingly useless.  So, my thought was that since
> my dad had his KX3 factory built, they did a proper RX Gain calibration.
> Since I didn't have a calibrated signal generator, I just used the factory
> defaults which maybe aren't so great?  My question is this: would it make
> sense to seek out a calibrated RF source and try and run a proper RX Gain
> calibration?  Would it likely solve my problem?
>
> Thanks,
> Travis
> K2NP
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