[Elecraft] K3 Receiver Noise Level -- Evaluation and Adjustment

[Wayne Burdick]

The K3 has a lot of overall gain. This is necessary to provide  
sufficient speaker output in operating locations with high ambient  
noise levels.

But you can adjust the amount of gain, and shape it, to meet your needs.

If you feel that the noise level of your K3's receiver is excessive,  
please try the following:

1. Turn off the preamp. In many cases it is not needed (especially  
below 20 m), because the receiver is still very sensitive working  
directly into the mixer.

2. If overall AF gain is higher than needed for your headphones or  
speaker, set CONFIG:AF GAIN to LOW. This makes the K3's audio output  
level (and overall gain) very similar to a K2.

3. Use the factory defaults for AGC. These were carefully chosen to  
adjust gain in the presence of significant band noise.

4. Use narrow filter bandwidths when listening to narrow-band modes  
(CW or DATA). Noise output is proportional to bandwidth, and in narrow- 
band modes, reducing WIDTH can dramatically reduce the signal-to-noise  
ratio. I strongly recommend installing at least one narrow crystal  
filter (500 Hz or lower) if you use CW or DATA modes. The K3's entire  
receiver philosophy is built around the use of roofing filters that  
are matched to the operating mode.

5. Use noise reduction. NR is specifically designed to reduce wideband  
stochastic (white) noise. I suggest using the lowest setting (F1-1) to  
obtain a modest noise-reduction benefit with minimum impact on signal  
characteristics.

6. If you're sensitive to high-pitched noise, consider installing (or  
having us install) the new DSP low-pass filter (LPF) module. (Contact  
k3support for details.) This filter rolls off everything at about 4.5  
kHz, including some low-level AF sampling artifacts from 10-14 kHz  
that some operators with excellent ears can hear. The LPF module,  
which is easy to install, can improve the overall listening  
experience. It has already been phased into production.

7. If you still feel that noise level is too high, try doing an MDS  
(minimum-discernable signal) test to see if the receiver is meeting  
spec. You can use your own signal generator or an Elecraft XG1 or XG2,  
in conjunction with the K3's built-in true-RMS AF voltmeter (see  
alternate VFO B display modes in the owner's manual).

73,
Wayne
N6KR