[Elecraft] K2 receive sensitivity

[Paul Del Negro]

Hi to all on the reflector.  I'd like to put something out here and see 
if others experience the same thing or if I possibly have a problem with 
my K2 sn5834.  Someone (I don't remember who) mentioned that a great way 
to test receive sensitivity is to simply check for an increase in noise 
level when switching from a dummy load to a resonant antenna on a dead 
band (like 10m is lately), and I am a great believer in that method.  I 
have used it for years with various commercial and homebrew rigs.
So here's the deal.  K2 set for 10 meters, preamp off, antenna is 
resonant wire (and also used a beam). When switching between dummy load 
and antenna, there is no (or barely perceptible) change in receiver 
noise output.  With the preamp on, the change is noticeable, as the 
noise increases both with dummy load and antenna connected.  What I'm 
concerned about is the preamp off situation, as all other receivers I 
have tested do show a marked change in receiver noise when doing this test.
I have already set the agc threshold so that there is no reduction in 
band noise when turning agc on and off.  Band pass filter alignment was 
done with a minimum signal from a signal generator and IF and filter 
alignments were done with  Spectrogram and everything seemed to check 
out OK.  BTW, the I used two antennas for this test, a 3 el tribander at 
40 ft and a OCF dipole cut for 160 and tuned with ATU. 
Do others have the same or similar results with this test?  I'd really 
like to know if my K2 is behaving normally or I have a problem.  BTW, 
the results improve as you lower the frequency, but the first band that 
shows a really marked increase in noise level with this test is 17m. 
Any and all comments are appreciated.
73, Paul, N2PD