[Elecraft] [K3] High internal noise level

[Pete Smith]

Thanks to Bill and everyone else for their suggestions.  I implemented 
N1EU's AGC settings - not much different from the defaults, but a 
little, and the receiver seems quieter.  Also switched off the 
peak-reading S meter, and the S-meter indication on a dummy load is now 
zero.  That may be the biggest psychological factor in the "quieter 
RX."  But boy, the S-meter seems scotch by comparison - I have done the 
calibration routine from the manual, though, and I'm satisfied that it's 
just honest - hi.

I guess my analog roots are showing - I have grown up used to running RF 
gain full on, and turning off AGC when I had to ride the RF gain.  But I 
notice that, as in an analog radio, the S meter is effectively disabled 
when you turn the RF gain down very far.  I guess I can live without it.

73, Pete N4ZR

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On 8/28/2010 7:21 AM, Bill W4ZV wrote:
>
> Pete Smith N4ZR wrote:
>    
>> Ever since I got my K3, I have been a little surprised at what seems to
>> be a relatively high noise level with no antenna connected (or on a
>> dummy load).  Very unscientifically described, on 20m it registers 1-2
>> bars on the S meter, and the background is quite loud on the speaker
>> with the audio gain set at 12 o'clock (RF gain full, AGC - fast,
>> bandwidth 200Hz with a 500 Hz roofing filter in, no noise blanker or
>> noise reduction).
>>
>>      
> Pete this is a common issue for new users.  It's actually not unique to the
> K3...Orion had the identical issue for the same reasons.
>
> 1.  Your gain settings are incorrect.  If AF Gain is at 12 o'clock it's too
> high, and RF Gain should almost never be at maximum.  My settings are
> typically AF Gain at 9-10 o'clock with RF Gain around 1-3 o'clock (but that
> depends on the specific antenna and band).  This has been covered many times
> and Barry N1EU has a nice explanation including a summary of how to set both
> gains here:
>
> http://n1eu.com/K3/K3_agcgain.htm  (scroll to Gain Adjustment)
>
>
> 2.  The K3's S-meter is more accurate than most rigs, especially at the low
> end of the meter scale.  Typical FT-1000 meters will read S1 at a -104 dBm
> level.
>
> http://www.n6rk.com/FT1000_S_meter.doc
>
> By contrast, a properly calibrated (and accurate) K3 meter will read S4 at
> the same level!
>
> http://www.n6rk.com/S_unit_definitions.doc
>
>
> The combination of #1 above (setting RF Gain to max) and #2 (an accurate
> meter which indicates higher than many rigs at low levels) leads many new
> users to think the K3 is noisy.  In fact it isn't but we need to learn how
> to properly set gain to take maximum advantage of the K3's dynamic range.
> K3NA's version is very detailed, but N1EU's version above is much simpler.
>
> BTW for those of you with a P3, setting it's Ref Lvl just at or slightly
> above the noise floor is the equivalent of what you're doing in the K3
> above.  When done properly with the K3, you'll hear weak signals at the
> noise floor and still have the full ~100 dB of dynamic range above that
> level.  If you set RF Gain too high, the rig will sound noisy and you'll be
> wasting some dynamic range by extending the K3's low end below band noise
> levels.
>
> 73,  Bill
>