[Elecraft] [K3] High internal noise level

[Bill W4ZV]

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
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