[Elecraft] K1 Noise Blanker

[Morrow, Michael A.]

From: Trevor Jacobs 

> Now upon building the NB I installed the LED rather than the second
> diode to give it a higher level of noise attenuation. The LO setting
> works great, but the HI setting doesn't do anything. The LED is
> installed as it should be (that was my first thought).
>
> The way I am reading things, I should see more noise attenuation 
> in the HI mode, OR, does it mean a HIgher threshold?

The HI setting sets the **threshold** higher.  A higher noise pulse
amplitude will be required to activate the NB, compared to the LO (low
threshold) setting.

Further, by installing the green LED option at D2, you have moved the HI
threshold even **higher** than what it would have been had you installed the
normal 1N4148 at D2.  You may want to go back and install the 1N4148
instead.

Thus, it is no surprise that you now hear very little effect when you are in
the HI setting.  It now takes a very large noise pulse to activate the
blanker.  As page seven of the KNB1 manual states, the LED should be used
only if you are in a high noise environment (i.e., the noise pulse
amplitudes are high).

73,
Mike / KK5F