[Elecraft] K3 receiver on 50 MHz

[Dave G4AON]

There have been some queries on the receive performance of the K3 on 50 
MHz and the possible need to improve it with an external pre-amp. I've 
just done a side by side comparison between my K3 and a Kenwood 
TS-480SAT on 50.1 MHz.

Mode CW, bandwidth on K3 400 Hz (400 Hz 8 pole filter). TS-480SAT has 
the YF-107C (500 Hz) filter. Pre-amp switched on in both transceivers.

There is nothing to choose between them, on my "uncalibrated" Marconi 
2018 signal generator, with 20 dB attenuator, The minimum signal level 
that I could copy a CW signal was -135 dBm on both (I could discern a 
slightly weaker signal, but that isn't really relevant for operating 
purposes). I'm not sure if -135 dBm is what everyone is expecting, but 
on the 480 I've worked plenty of DX and hearing stations is not an 
issue, even on an electrically quiet hill. To save anyone looking up the 
conversion to micro Volts, -135 dBm = 0.04 uV.

73 Dave, G4AON
K3 #80