Don Wilhelm wrote:
Paul,
I am not certain your test is entirely valid. If there is no atmospheric
noise on the band you are using, you should notice no difference in level
switching from a dummy load to an antenna.
The bandwidth of the receiver will make a great difference as well, and that
is both the IF bandwidth and the front end bandwidth. The K2 does have the
low pass filters at the receiver front end - some other receivers run with a
wide open 'DC to Daylight' front end which will pick up more wideband noise.
You are not necessarily comparing apples to apples with such a simplified
subjective measurement.
It would be much more informative to actually measure the MDS at a given
receiver bandwidth and at the frequency of interest. Measurements of that
nature should be controlled and can be used for valid comparisons.
73,
Don W3FPR
-----Original Message-----
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.
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11:04 AM
Thanks for your reply, Don... it has been my experience that there is
always some level of atmospheric noise on 10 meters, even when the band
is not open. The method of sensitivity quick-test I described was
endorsed by many notable amateurs, including the late Doug DeMaw, W1FB,
who I'm sure you have heard of. That's where I got the method from.
But I guess what I'm asking of the guys on the reflector is whether or
not they are experiencing the same result using this quick-test with the K2.
72 Paul N2PD
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