A Question From a Dummy - Regarding : [Elecraft] Noise generator

[Ron D'Eau Claire]

The "noise generators" referred to here are actually "white" noise
generators. That is, they produce random noise that is uniform in =
amplitude
across a large portion of the RF spectrum. If you look at their output =
on a
spectrum analyzer, the display turns "white" with the broad-band RF =
"noise"
across the RF spectrum, which is what gives them their name.=20

Such a noise generator is useful for "peaking" the tuning of r-f =
amplifiers
in receivers and evaluating the bandpass characteristic of RF/I.F. =
stages.
In the case of the Elecraft rigs, it finds its greatest use with
"spectrogram" - a software spectrum analyzer that runs on a personal
computer - to adjust and observe the bandpass characteristic of the I.F.
amplifiers. If you tried to do that with a normal signal generator, =
you'd
have to sweep the frequency slowly across the bandpass and note the =
output
from your K2 every few Hz to plot the "curve" of the I.F. filters by =
hand.
The noise generator produces uniform RF at all of the frequencies of
interest at once, so you can see the whole bandpass at a glance.=20

A noise generator is handy but not at all essential for aligning a K2. =
There
is PLENTY of noise on the lower HF bands for this purpose. But using one =
has
some advantages:  It eliminates the need to hook up an antenna to pick =
up
the noise. It avoids finding signals in the bandpass which can confuse
readings. And it ensures that the noise is uniform and broad.=20

Where a noise generator really becomes important is when you get above =
the
frequencies at which there is plenty of "atmospheric" noise. When the =
bands
are quiet, it can be hard to find enough atmospheric noise above 21 to =
30
MHz at times. Above 50 MHz, it becomes very rare to hear enough
"atmospheric" noise to align a receiver and a good "noise generator" is
essential.=20

And, don't forget, Elecraft is about to break loose with some =
transverter
kits for the 50 MHz and up range... <G>

Another way a noise generator is quite useful is in troubleshooting. You =
can
make up a test probe (with a d-c blocking capacitor to be sure you don't
short any d-c voltages) and touch it to the inputs of stages in the =
RF/I.F.
sections of a receiver to see if each stage is working. By comparing the
loudness of the noise in the speaker when it is injected at each stage, =
you
can get a rough idea of whether or not the stage has gain. If you start =
at
the product detector and work toward the antenna touching the probe to =
the
input of each stage a 'dead' stage is obvious because suddenly the noise
will disappear or the level will be much lower than it was.=20

Ron AC7AC
K2 # 1289

-----Original Message-----
Hi,
  Can someone tell me if I should be interested in acquiring a noise
generator? (my kids are grow, and I kind of like the peace and quiet).
Serously, though, what will it do?  Is it similar to a signal generator =
to
be used for tracing signals?

Inquiring minds want to know.

Thanks for any help on this, from a clueless ham.

Tom McCulloch
WB2QDG
K2 s/n 1103 (silent while patiently awaiting a new MCU :((   )