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

It's not clear to me what noise you're trying to measure. If you're
trying to measure the thermal noise of a good resistor, you're SOL --
anything you try to measure it with will add its own noise, which you'll
end up measuring instead. You can easily calculate the thermal noise,
though. If you're trying to measure the internal noise of the spectrum
analyzer, the answer is on the screen and, as you've found, it's a
function of the filter bandwidth. If you're trying to measure the noise
coming from a receiver, it has to be considerably greater than the SA's
internal noise, or you'll never see it. That means you'll have to
amplify it until you can see it, with an amplifier that's quiet enough
that the noise it adds isn't significant. The noise figure of the SA
itself is typically much worse than a decent receiver -- it's been
traded for dynamic range.

Once you get whatever noise you're trying to measure up to the level you
can see it on the SA, you'll find that its magnitude also varies with
the SA filter bandwidth, if the noise is broadband. You can get any S/N
ratio you want, if you can tolerate an arbitrarily narrow bandwidth. A
real receiver has some particular bandwidth to accommodate the incoming
signal. It's usually this bandwidth at which the S/N ratio is measured.

Roy Lewallen, W7EL

Bill B. wrote:
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

Hi Bill,

Welcome to the wonderful world of posting.

I'd expect noise levels to be specified in (nano)volts per sqrt(Hz),
or (femto)watts per Hertz. This can be experessed in dBm, too, of
course. If you know the noise bandwidth of the filter the SA is
putting the signal through, then you just take the measured noise
floor and adjust it by the ratio of that bandwidth to 1 Hz. So if it
were a 10Hz noise bandwidth, the noise per Hz would be 10dB below what
you see. If the filter is 100Hz, it would be 20dB below. Now, is the
noise bandwidth of the filter the same as the resolution bandwidth?
Not necessarily, but it should be fairly close, generally within a few
percent. We build FFT-based spectral analysis equipment, and have to
document the noise bandwidth of the effective filters, but we also
generally have a way to directly display "noise density" which is
already in v/rt(Hz) or w/Hz or dBm -- so it's worth looking to see if
the analyzer MIGHT have such a function. -- It's worthwhile because
of the variation from measurement to measurement to use as much
averaging as is convenient. This might be called "video filtering",
but is done after the signal filtering and detection. Lessee...what
else. Normally, the base level noise of the analyzer would be
measured with the input terminated in its input resistance, usually 50
ohms.

Footnoote about the bandwidths: the noise bandwidth (or noise power
bandwidth) says if you have an input signal of, say, 1.000 picowatts
per Hz, and it's uniform power density per unit bandwidth (a flat,
broadband noise), and you measure 12.345 picowatts coming through your
filter, then the noise bandwidth is 12.345Hz. That may differ from
the -3dB bandwidth of the filter, though generally not by a huge
amount. With analog filters, it's probably expecting a lot for it to
be really the same from analyzer to analyzer of the same model, but
with digital filters (not necessarily even FFT-based), it should be
spot-on the same from one to the next.

Cheers,
Tom

(Bill B.) wrote in message . com...
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

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

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

I assume these unit are the unlicensed variety and use spread spectrum
technology (frequency hopping)? If interference is the cause, it may be
hard to find since you probably don't know the discreet frequencies used
in the hops. If I am understanding you correctly, you are looking for
the ambient level of noise coming down your coax to the radio? I know
just enough to be dangerous as far as spectrum analyzers go. We just
plug the coax into the analyzer and see where the "fuzz" is located at
the bottom of the display, i.e. -108 dbm.

I am not familiar with the radio you are using, but if it like the ones
we use, can you swap frequency bands such as Band A or Band B? We have
some Lynx and Tsunami 2.4 GHz T1 radios where the back filter unit comes
off and we invert it to select another band of frequencies. Might be
worth a shot if you can do it (to both ends of course!)...

Good luck! Let us all know what you find!!

Scott
N0EDV


Bill B. wrote:
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
.com...

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

Your Software Must be robust enough to accept, reject and process corrupt
packets as you will Always get them with wireless, always. --You will ALWAYS
have bad/corrupted packets with any wireless system.-- The 5 band antennas
have very splintered patterns, and ducting from point to point. and you will
have +20dB one second and -20 the next second, your firmware, and software
must handle this stuff, RF cannot do it alone. Mother nature set the rules
on this one.

The MFGR will tell you the max range, and the dishes to use, rain degrades
the signal, as well as heat (ducting) The big boys use 4 dishes for a link
ATT @ 11 Gigs two on each side spaced vertically some so when ducting
occures, the other dish picks it up. If the cost is low enough, you could
put in another entire link as backup. Also % of packets getting though is
an indicator of SNR, but that can depend on how you have the link hooked up,
as a LAN extention, you have timing constraints, and so on. 90% or better
is great. Less than 20% you may have a link or LAN timing problem (path too
long, pointing is off, ducting, SW lame).

On a roof in Boston, your 5 gig unit may be susceptible to radio and TV
interference, the scan may be detected on a junction in the unit. Signal
blasts through the case and so on. Urban RF is a dirty world, and we can't
see it either!




"Bill B." wrote in message
...
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

"Roy Lewallen" wrote in message
...
[...snip...]
If you're trying to measure the noise
coming from a receiver, it has to be considerably greater than the SA's
internal noise, or you'll never see it.


Assuming classical "noise" as we are all probably thinking...
First, a minor correction to the above "considerably greater", Roy. If the
EXternal noise is just 6dB above the SA's INternal noise (I guess 4 times
can be considered 'considerable'), then the resulting displayed value will
be only 1 dB higher than the incomming noise actually is. Noise power (when
combining in one receiver) simply adds. To see the math, think this way. A
1 dB increase amounts to 1.25 times the power. That extra 25 percent is one
fourth the original power. 25% of the power is 6dB down from the original.
SO adding some power which is -6 dB (or 25% the original) will raise the
total 1 dB.

However, The poster used the term "noise", but doesn't know the source of
his problem. His data hits can be caused by other than what we are thinking
is noise. It can be (sounds like since it recently started) spurious
signals in his channel OR it could be IM being caused from strong signals
getting into his receiver. The spurious in-band stuff could be narrow
signals or wideband. Typical CDMA signals behave much like simple wide-band
noise as we think of noise. A narrow band signal/spur is different.

From a later post I see that he is trying to measure some junk that has
appeared on the link frequency causing interference. In any case, the
front-end noise floor (noise figure) of the SA will determine how far down
you will be able to see and if it is not low enough, then you won't see the
interference. I can not comment on the Advantest sensitivity. If you have
access to a low noise amplifier of the type used in your system, it can be
used in front of the SA and *MAY* raise the sensitivity (lower the noise
figure/floor) enough to see yout interference.

Good luck. We've had a strange low level (around -123 dBm)spur on our
repeater input since last fall and can't locate it...wish I had lotsa time.
--
Steve N, K,9;d, c. i My email has no u's.