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

John Smith wrote:
"The big boys use 4 dishes for a link."

Yes. It is for space diversity which dramatically improves reliability
on many paths. Paths tend to fade independently when they are
significantly separated, say by 10 wavelengths.
More than just 2 antennas at a path end is required for diversity
reception. Separate receivers are required too.

Two dishes connected together just make an antenna array. If both
receive the same signal, it is probable a time will come when the signal
sum is zero even though either signal is usable.

Two receivers or more must be used for space diversity reception. A
special combiner must be used to select the best signal and reject all
others. Individual receivers are connected with individual antennas and
selection is made from among the receiver outputs. All other receiver
outputs are completely rejected.

The shortwave broadcaster I worked for in the 1950`s relayed its
programs via HF radio. There were 3 rhombic receiving antennas,
separated by about 10 wavelengths broadside, at the lowest frequency.
This was repeated for each reception direction. Each rhombic fed its own
multicoupler in the receiving station. A receiver for each frequency
being received was connected with an output from a multicoupler.The
receivers were all Hammarlund SP-600`s.

Three receiver outputs, representing signals from each of three antennas
were fed to a "triple diversity combiner" (Crosby or Pioneer). The
combiner selscted the best of the three signals and rejected all others.
This is a triple diversity reception, "TDR System".

In the 1960`s, I built a diversity microwave system into the Gulf of
Mexico from onshore. Water can often reflect well enough for complete
signal cancellation at microwave frequencies, so I used space diversity,
two dishes vertically separated on the towers, feeding separate
receivers at each path end. Only one transmitter at each end of a path
operates at a time., but both receivers work with a combiner which
functions like that used at HF for the TDR. Output is a video type
spectrum rather than audio output as from the TDR combiner. The video
combiner picks the better of the two received demodiulated microwave
signals and rejects the poorer signal. It works like Gangbusters.

Best regards, Richard Harrison, KB5WZI