[Elecraft] Alligators

[Ron D'Eau Claire]

Good points, Jim, but WHY run the pre-amp on 80? The K2 has a noise =
figure
way, way below the band noise on even a short piece of wire on 80 meters
without the pre-amp.

The pre-amp is needed to pull really weak signals up above the receiver
noise floor on 15 or 10 meters, but it shouldn't be needed below that.=20

The K2 noise blanker is effective against clear 'impulse' noise (like a =
few
cheap lamp dimmers in my neighborhood) and that is one place where I =
will
occasionally turn on the pre-amp on the lower bands. Sometimes, even on =
low
threshold, the pulses don't trigger the NB unless I boost everything =
with
the pre-amp. Then the pulse noise drops out even though the overall =
noise
floor is much higher than needed. Still, it improves copy.=20

The noise blanker, because it is a non-linear device literally "chopping
holes" in the received signal can also add "noise" of it's own in the =
form
of an increased background level.=20

Ron AC7AC

-----Original Message-----
Subject: [Elecraft] Alligators
...it's also important to remember that many guys are stuck with some =
pretty
high noise levels. That's my problem on 80 and 40 -- my dipole at 45 ft =
sees
an S8 on 40 and S9 on 80 with crystal filter set to use the SSB filter =
and
the preamp on. Of course I can pull that level down a lot by going to
narrower bandwidths, but the noise level generates a lot of ringing due =
to
the filter slopes.  Signals were quite good on 40, especially Friday =
night,
so I was able to work a lot of DX on that band in spite of the noise. =
But I
could only hear a few of the stongest DX signals on 80, and made only =
about
25 QSO's there.=20

For all practical purposes, the noise blanker in my K2 does nothing at =
all
with this noise. The blanker in my Omni V is somewhat effective, =
sometimes
reducing it by a couple of S-units. When I have time, I'm going to
experiment with an active antenna noise canceller that I bought on EBay. =


Jim Brown
K9YC