This is a time-lapse shot comparing what you think your nice noise floor
is,
and what it REALLY is after letting all the crap accumulate in peak
hold mode.
Regardless, unless there's a pre-amp on the input to this analyzer
(notice the ref level
of 40.4 dBmV), there's still a bunch of noise under the bottom trace
that would make
using this return spectrum rather difficult!
Knowing Jim, I'm guessing a pre-amp is on the input to not only provide
an extra 20 dB
or so, but to also act as a low pass filter (depending on pre-amp brand)
to keep forward
carrier power (depending on test point) from overloading the analyzer
input.
(Courtesy - Jim Kuhns)
Another "decent looking" floor with what looks like a shortwave spike
and some impulse
noise attempting to make a showing. Notice the ref level of 39.7 dBmV.
Again, a pre-amp was also probably used on the input of this analyzer
shot.
Of note: If a 24 or 25 dB gain pre-amp WAS used, the rise in floor
at the lower end
could be a result of the pre-amp response, or a low battery in the
pre-amp if it were
indeed a battery powered unit.
ALWAYS sweep your pre-amp to ensure proper compensation for
its particular characteristics prior to using it in the field!
(Courtesy - Jim Kuhns)
A basic carrier to crap depiction utilizing a CW generator (probably
an old Wavetek - hehe),
and analyzer Delta marker function. Notice the 41.26 dB C/C ratio.
The "crap" appears to be
RF ingress - most likely shortwave. The rest of the floor looks mighty
nice! (Again - providing a
pre-amp was used on the input to the analyzer.) Though the floor looks
pretty and the Delta is nice,
-10 dB for a return floor is still junk unless a 25 dB gain pre-amp
has been used for this shot.
(Courtesy - Jim Kuhns)