Thank you so much for all your help (Crazy George, Roy, Tom, John)!! Per
Crazy George's suggestion, I am picking up some books tomorrow at Borders
grin. However, the posts that I received were very helpful. Let me explain
a little more what I am trying to do, just to see if I am even close to the
right track. We have a Microwave link that operates at 5 GHz... specifically
one sides transmits between 5.25-5.25GHz and receives at 5.725-5.825 GHz.
The product we are using for this link is a Stratum 100 (
http://www.commputercations.com/products/wsstratum.htm - The only datasheet
I could find ). This link went down hard a few days ago, so we switched
polarization (From Horizontal to Vertical). Things got much better, but we
still were taking corrupt packets. So, we went out there with an Advantest
R3465 SA ( http://www.ntecusa.com/graphics/pdf/WE106.pdf ), an Omni antenna,
and 10 degree directional dish, with the hopes to (1) look at the "same"
noise floor that the Stratum sees and (2), try to track down any single
direction (And hopefully antenna) that is causing interference. Now, I
thought I knew this stuff grin, at least enough to retrieve somewhat
accurate results. Boy was I wrong! I scanned the receiving frequencies using
the following settings:

Start Freq: 5.725GHz
End Freq: 5.825GHz
Span: 100MHz
RBW: 5 MHz
VBW: 1 MHz
Sweep Time: 50ms
ATT: 10dB
REF: 0.0dBm (10dB/)

Knowing what I know now, I would have kept the RBW value MUCH lower (Like
10kHz). But what I saw was a "noise floor" - Which I was assuming to be (I
believe) the Thermal noise floor which I now know to be the Filter Noise
Floor, peaking out at about -64dBm. Now our receive strength when the radio
is on is -65dB... So I figured "Hey, there is our problem... the receiver in
the Stratum unit is seeing the noise floor so loud that it can hardly see
the actual signal". What makes this even more believable is that these
readings were taken in the middle of Boston on the 26th floor roof. So I
packed up and went home... Then I tried the same test at my fairly isolated
house... and got the same results!

Now I know there is at least one answer to how to avoid this embarrassing
situation in the future... read a book (Which I will start tomorrow)...
however, I really would like to get this link up in short order and need to
know these numbers. Am I correct in saying that I need to (1) contact the
manufacture of the Stratum unit, and find out what their Bandwidth filter
looks like and then (2), Set my RBW to the same or lower setting as their
radio and do the test again?

If the above two steps are correct than great... I can do that... but I
really would like to make use of the measurements I already took if
possible.

Again, I really appreciate the comments from before. While I don't yet
understand all of it, these really point me in the right direction, and I
will keep reading/researching until it all comes together.

Thank you,
Bill B. - N1SNI

"John Smith" wrote in message
...
What is the "Bandwidth" of the "stuff" you are trying to measure?
You could set the analyzer to that or a little less, and then use relative
measurements.
You may need more gear if you are trying to measure a very low noise
wideband preamp.
Depends on what you are trying to measure.
Bigger bandwidth=higher noise floor, simply kTB. and it is a ratio if you
change kTB1/kTB2= B1/B2 (10 log it of course)

If you have the analyzer on, then connect the gizmo without signal and the
noise floor rises up 10 dB or more, you could probably ignore calculating
what the SA contributes. just add signal and it should be 6 dB or more
above
noise floor established by your gizmo.

If not, then It is possible to calculate almost exactly the noise floor
on
the analyzer to verify what is displayed is good, but you need a number or
two from the MFGR of the analyzer, which takes into account the filter
shape
of the analyzer. (0.8 ot 1.6 something like that)

SAs are cool! What type do you have, makes a big difference, (depending on
what you are trying to measure) Some will not do it.


"Bill B." wrote in message
om...
Hello,
I need some help in figuring out how to properly use a Spec. Analyzer.
I have done several hours of research online now, and have somewhat of
an idea of what I am doing, but I just can't get down one piece of the
puzzle. In my line of work, we use simple devices that give us the
noise floor level in dB. I (stupidly) expected to be able to get this
same information easily out of a SA. As you may have guessed by now, I
ran into a problem when switching the RBW value. After much... much
reading, I fully understand *WHY* it changes (Filters increasing in
size cause a greater internal noise level, etc.) but I can't figure
the best way to get a "base" noise level reading. And as much as I
would like to fully understand the theory, what I really need is a few
more examples... IE: If you are looking a 100 MHz span and your RBW is
1MHz simply ___Fill in the Blank____ to find the base noise floor. To
further explain what I am trying to do, we are setting up a link that
requires a SNR of at least 6dB... I need to get the noise floor level
to compare with my projected signal strength for this link.

Please be nice... This is my first post grin

Thank you! Thank you!

Bill B. - N1SNI