[Elecraft] K3 Audio Pops

[Randy Farmer]

I used my K3 for the first time in a really serious contest for SS 
CW. The performance was astounding. This is the first receiver I have 
EVER had that would let me put a S9 +40dB signal just on the edge of 
the filter and then copy signals in the filter passband clear down to 
the noise floor with no problem at all.

However, I did notice at times that there were a good many loud 
"pops" that appeared in the audio, seemingly at random. These pops 
were really LOUD, but fortunately very brief (maybe just a few 
milliseconds in duration). Since the pops were so much louder than 
the normal audio, I can't say for sure that their level changed with 
the audio gain setting. They sounded to me like DSP artifacts, as if 
the audio D/A was being driven to the top of its range for short 
periods. I wasn't able to really correlate these pops with anything I 
was hearing within in the receiver passband. During one run period on 
40 meters the pops were especially frequent, coming every few 
seconds. Probably not coincidentally there was a nearby station who 
had some rather prominent key clicks, and I'm guessing the 
combination of his key clicks and local QRN spikes were aggravating 
whatever mechanism is responsible for the pop generation.

The pops were encountered in "plain vanilla" receive mode, no NB or 
NR and mostly with the default 400 Hz DSP bandwidth behind an 8-pole 
400 Hz 1st IF filter, QSK on. I'm running the latest public beta 
firmware (MCU 3.52, DSP 2.43). If it makes any difference, I do have 
my radio set to select the 400 Hz roofing filter when the BW is 
dialed to 500 Hz rather than the default 400 Hz. I heard the pops 
using either of two kinds of high impedance headphones, Sony MD-7506 
(63 Ohms) and Extreme Isolation EX-29 (32 Ohms).

Has anyone else encountered this phenomenon?

73...
Randy, W8FN