[Elecraft] [K3] RX Gain Calibration

[Travis Brown]

Thanks Don.

I will definitely tweak the AGC settings. Someone else recommended that
too. However, I thought the KX3 and K3 had basically the same receiver, and
if I hook the KX3 up to the same antenna that to which my K3 was connected,
the S-meter should report the same values regardless of the AGC setting,
correct?

Thanks,
Travis


On Mon, Mar 18, 2013 at 9:11 AM, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> 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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