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-   -   spectrum analyser (https://www.radiobanter.com/homebrew/20837-spectrum-analyser.html)

payam July 21st 03 03:35 PM

spectrum analyser
 
hi, where can i find practical high fre spectrum analyser circuit?
thanks

Hans Summers July 21st 03 03:50 PM


"payam" wrote in message
om...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


If by High Frequency you mean up to 30MHz, mine is quite practical and goes
up to about 140MHz
(http://www.hanssummers.com/electroni...ctrumanalyser/). If you
want UHF then try a google for "homebrew spectrum analyser", brings loads of
good links.

72 Hans G0UPL



Hans Summers July 21st 03 03:50 PM


"payam" wrote in message
om...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


If by High Frequency you mean up to 30MHz, mine is quite practical and goes
up to about 140MHz
(http://www.hanssummers.com/electroni...ctrumanalyser/). If you
want UHF then try a google for "homebrew spectrum analyser", brings loads of
good links.

72 Hans G0UPL



John Miles July 21st 03 11:52 PM

In article ,
says...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

John Miles July 21st 03 11:52 PM

In article ,
says...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

Joel July 22nd 03 01:02 AM

I built the 'Poor Man's Spectrum Analyzer' a whole lot of years ago. While
it does work, it leaves a lot to be desired.. The resolution isn't very
good and I would hate to make any judgments on equipment performance based
on it. I think it's an interesting project and I'll just leave it at that.

Joel AG4QC



Joel July 22nd 03 01:02 AM

I built the 'Poor Man's Spectrum Analyzer' a whole lot of years ago. While
it does work, it leaves a lot to be desired.. The resolution isn't very
good and I would hate to make any judgments on equipment performance based
on it. I think it's an interesting project and I'll just leave it at that.

Joel AG4QC



Hans Summers July 22nd 03 11:21 AM


"Ian White, G3SEK" wrote in message
...
Hans Summers wrote:

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you

think
it's superior to the poor man's spectrum analysers based on CATV tuners?

The
latter surely have greater frequency coverage. But in what ways are they
inferior


A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.

The problem is that real incoming signals and the analyser's spurious
responses all look very much the same on the screen. When you can't
trust what the analyser says, it becomes very hard to understand what's
really going on.

As with lots of beginner-level test equipment, it sometimes needs an
expert to understand it!

CATV tuners and low-level NE602 mixers are simply not the building
blocks for a high dynamic range receiver. The W7ZOI design uses much
more appropriate building blocks so its readouts are much more
trustworthy.


I used two SA602A mixers in my design (see
http://www.hanssummers.com/electroni...ctrumanalyser/) and get
about 60 or 70dB of on-screen dynamic range. The SA602A approach does have
the advantage of similicity, at the cost of reduced performance. I use one
SA602A with the on-chip oscillator as the VCO swept from 145 to 290MHz with
145MHz IF output. The 2nd SA602A has 153MHz fixed on-chip oscillator and
mixes down to the 8MHz 2nd IF.

Spurious responses in my analyser from strong signals aren't usually a
problem except at the upper end of the frequency coverage. The W7ZOI
analyser covers 0-70MHz, mine 0-140MHz. It would be very interesting to
compare my design against a W7ZOI analyser over the same frequency range,
i.e. place a 70MHz low pass filter ahead of my analyser. I suspect spurious
reponses would be comparable, but on-screen dynamic range somewhat less in
my analyser.

My analyser Mk2 is already under construction and will aim to provide masses
more features, greater coverage, and improved dynamic range performance.


and can you quantify it?

Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


What if you don't have another analyser ;-) Part of my intention with my
simple analyser was to build something straightforward but still extremely
useful, and do so without access to much other test equipment. When I have
the Mk2 up and running it will be interesting to compare.

73, Hans G0UPL



Hans Summers July 22nd 03 11:21 AM


"Ian White, G3SEK" wrote in message
...
Hans Summers wrote:

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you

think
it's superior to the poor man's spectrum analysers based on CATV tuners?

The
latter surely have greater frequency coverage. But in what ways are they
inferior


A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.

The problem is that real incoming signals and the analyser's spurious
responses all look very much the same on the screen. When you can't
trust what the analyser says, it becomes very hard to understand what's
really going on.

As with lots of beginner-level test equipment, it sometimes needs an
expert to understand it!

CATV tuners and low-level NE602 mixers are simply not the building
blocks for a high dynamic range receiver. The W7ZOI design uses much
more appropriate building blocks so its readouts are much more
trustworthy.


I used two SA602A mixers in my design (see
http://www.hanssummers.com/electroni...ctrumanalyser/) and get
about 60 or 70dB of on-screen dynamic range. The SA602A approach does have
the advantage of similicity, at the cost of reduced performance. I use one
SA602A with the on-chip oscillator as the VCO swept from 145 to 290MHz with
145MHz IF output. The 2nd SA602A has 153MHz fixed on-chip oscillator and
mixes down to the 8MHz 2nd IF.

Spurious responses in my analyser from strong signals aren't usually a
problem except at the upper end of the frequency coverage. The W7ZOI
analyser covers 0-70MHz, mine 0-140MHz. It would be very interesting to
compare my design against a W7ZOI analyser over the same frequency range,
i.e. place a 70MHz low pass filter ahead of my analyser. I suspect spurious
reponses would be comparable, but on-screen dynamic range somewhat less in
my analyser.

My analyser Mk2 is already under construction and will aim to provide masses
more features, greater coverage, and improved dynamic range performance.


and can you quantify it?

Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


What if you don't have another analyser ;-) Part of my intention with my
simple analyser was to build something straightforward but still extremely
useful, and do so without access to much other test equipment. When I have
the Mk2 up and running it will be interesting to compare.

73, Hans G0UPL



[email protected] July 22nd 03 02:58 PM


My analyser Mk2 is already under construction and will aim to provide masses
more features, greater coverage, and improved dynamic range performance.


Why not go for the minicircuits +14dBm high level mixers ? ... their quite lossy
(around 9dB loss) but that can be over come. They do need a fair bit of LO
drive though (50mW) but that's no real problem these days, a couple of +18dBm
MMIC's (ERA's etc) in push pull mode should guarantee that level of power and
hopefully give you 3db more than needed so you can use 3dB pad's around the
mixer.

Clive


[email protected] July 22nd 03 02:58 PM


My analyser Mk2 is already under construction and will aim to provide masses
more features, greater coverage, and improved dynamic range performance.


Why not go for the minicircuits +14dBm high level mixers ? ... their quite lossy
(around 9dB loss) but that can be over come. They do need a fair bit of LO
drive though (50mW) but that's no real problem these days, a couple of +18dBm
MMIC's (ERA's etc) in push pull mode should guarantee that level of power and
hopefully give you 3db more than needed so you can use 3dB pad's around the
mixer.

Clive


Hans Summers July 22nd 03 04:33 PM


Tnx, it's certainly one of the things I'm considering. That's more effort
than an LC tank on a couple of SA602 pins. But I guess for higher
performance you need higher complexity.

73 Hans G0UPL

wrote in message
...

My analyser Mk2 is already under construction and will aim to provide

masses
more features, greater coverage, and improved dynamic range performance.


Why not go for the minicircuits +14dBm high level mixers ? ... their quite

lossy
(around 9dB loss) but that can be over come. They do need a fair bit of

LO
drive though (50mW) but that's no real problem these days, a couple of

+18dBm
MMIC's (ERA's etc) in push pull mode should guarantee that level of power

and
hopefully give you 3db more than needed so you can use 3dB pad's around

the
mixer.

Clive




Hans Summers July 22nd 03 04:33 PM


Tnx, it's certainly one of the things I'm considering. That's more effort
than an LC tank on a couple of SA602 pins. But I guess for higher
performance you need higher complexity.

73 Hans G0UPL

wrote in message
...

My analyser Mk2 is already under construction and will aim to provide

masses
more features, greater coverage, and improved dynamic range performance.


Why not go for the minicircuits +14dBm high level mixers ? ... their quite

lossy
(around 9dB loss) but that can be over come. They do need a fair bit of

LO
drive though (50mW) but that's no real problem these days, a couple of

+18dBm
MMIC's (ERA's etc) in push pull mode should guarantee that level of power

and
hopefully give you 3db more than needed so you can use 3dB pad's around

the
mixer.

Clive




John Miles July 22nd 03 10:29 PM

In article ,
says...

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you think
it's superior to the poor man's spectrum analysers based on CATV tuners? The
latter surely have greater frequency coverage. But in what ways are they
inferior and can you quantify it?


Apart from what Ian said, it's also really important to have a stable
LO. If you don't -- i.e., you're relying on an inadequately-stabilized
cable TV tuner -- you can only tell if a signal is present or absent.
You can't tell much about its stability and noise level, or look for
close-in IMD products. Narrow resolution bandwidths require stable LOs.

I haven't used a W7ZOI analyzer myself, but it ought to be at least an
order of magnitude more stable than any CATV implementation. It would
indeed be interesting to see a spec-for-spec comparison between the two.

Either way, they make great educational projects. :)

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

John Miles July 22nd 03 10:29 PM

In article ,
says...

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you think
it's superior to the poor man's spectrum analysers based on CATV tuners? The
latter surely have greater frequency coverage. But in what ways are they
inferior and can you quantify it?


Apart from what Ian said, it's also really important to have a stable
LO. If you don't -- i.e., you're relying on an inadequately-stabilized
cable TV tuner -- you can only tell if a signal is present or absent.
You can't tell much about its stability and noise level, or look for
close-in IMD products. Narrow resolution bandwidths require stable LOs.

I haven't used a W7ZOI analyzer myself, but it ought to be at least an
order of magnitude more stable than any CATV implementation. It would
indeed be interesting to see a spec-for-spec comparison between the two.

Either way, they make great educational projects. :)

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

Avery Fineman July 23rd 03 02:06 AM

In article , "Ian White, G3SEK"
writes:

Hans Summers wrote:

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you think
it's superior to the poor man's spectrum analysers based on CATV tuners? The
latter surely have greater frequency coverage. But in what ways are they
inferior


A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.


"Meaningful results" are subjective to the hobbyist.

NO analyzer means NO results.

If I were designing a spectrum analyzer for the electronic instrument
market, I would shoot for at least meeting Hewlett-Packard Agilent
or Rhode&Schwarz specifications...R&D budget willing. That's a bit
steep for the hobbyist area.

The problem is that real incoming signals and the analyser's spurious
responses all look very much the same on the screen. When you can't
trust what the analyser says, it becomes very hard to understand what's
really going on.


Sigh. A spectrum analyzer, almost ALL of them, is one of the easier
instruments to characterize from the outside, using other instruments.
Frequency span, logarithmic linearity, passband of the final IF are all
relatively easy to determine from the outside.

So what if a spectrum analyzer isn't "perfect?" It is much, much
better than having NO spectrum analyzer.

The majority of spectrum analyzer input signal levels are most likely
to be UNDER -10 dbm. That input level is not - generally - going to
cause all kinds of "imperfections" in the viewed spectrum.

As with lots of beginner-level test equipment, it sometimes needs an
expert to understand it!


I disagree. There are any number of application notes free for the
downloading on the Internet, from Agilent they are copies of older
(two decades at least) FREE paper application notes. Agilent also
has free application notes on the basic building blocks within an
analyzer and much information on the characteristics of those blocks.

CATV tuners and low-level NE602 mixers are simply not the building
blocks for a high dynamic range receiver. The W7ZOI design uses much
more appropriate building blocks so its readouts are much more
trustworthy.


Yes, its possible to "conquer" the dreaded too-high-signal IM mountain
peaks with high-level mixers and higher-milliWatt first LOs. See Mini-
Circuits' catalog as one place for modules.

I haven't seen the "W7ZOI design" so I won't critique it at all. Having
used spectrum analyzers for about 4 decades, the high-input-level IM
bogeyman seldom goes "boo!" for most spectrum observation. That
includes transmitter output monitoring.

and can you quantify it?

Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


Have you priced the used spectrum analyzers lately? Do you expect
others to have ready access to "another" spectrum analyzer?

In checking my own little special-purpose IF strip Sweeper (a quasi-
spectrum-analyzer), I am fortunate to have a pair of H-P rotary step
attenuators (salvaged, checked for calibration by another) to determine
if the Log response curve of the Analog Devices chip is correct...rather
very basic stuff. Unfortunately, the accuracy of the external attenuator
is about the same as the AD accuracy. I'd love to have a Weinschel
Precision Bench Attenuator to use as a comparison, but don't, can't
afford one.

I do have a very good pair of H-P signal generators (very much previously
owned) which have been put in order by a good friend of mine. With the
help of an outboard lowpass filter (easy to make) which is also
characterised by response testing using a linear detector, I can guarantee
an RF signal with all harmonics down 60 dbc. The RF power output of
those generators is also separately characteriseable/calibrateable within
2 db of absolute level at the high-power output (0 dbm) all the way down
to -120 dbm, probably lower. The lower levels are determined by a
waveguide-below-cutoff internal attenuator which hardly ever jumps out of
calibration unless the mechanicals get goofy. The Weinschel attenuation
standard uses the same basic below-cutoff principle.

With all of the above (two generators, overlapping ranges) I can absolutely
guarantee a true "two-tone" testing setup for an analyzer to determine
what the 1 db or the 3 db IM values are of any receiver front end. So far,
I've never ever seen any cause for concern with any input level up to -10
dbm. Have I ever done any such? Of course, even checking out a used
(and rare) Tektronix spectrum analyzer plug-in on a borrow.

I have YET to encounter any receiver input that goes higher than -10 dbm
equivalent input with the one exception of being within two blocks of
local AM broadcast station KMPC pushing 50 KW into their antennas.
I'm sure there are all kinds of "exceptions" to that and I'm sure there will
be commentary coming back on that. :-)

I'm not going to get in about the relationship of sweep rate and final SA
IF resolution...which are VERY important in SA work, particularly in
relatively narrowband observations. Close-proximity signals can "hide"
if wide resolution IFs are in place...that "hiding" visible at input RF
levels
well below ANY intermodulation distortion level. The resolution aspect of
practical SA design is a separate matter but should not be forgotten..

When push comes to shove in all this, I'd say that SOME KIND of
spectrum analyzer is a LOT better than NONE. EOF.

Len Anderson
retired (from regular hours) electronic engineer person

Avery Fineman July 23rd 03 02:06 AM

In article , "Ian White, G3SEK"
writes:

Hans Summers wrote:

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you think
it's superior to the poor man's spectrum analysers based on CATV tuners? The
latter surely have greater frequency coverage. But in what ways are they
inferior


A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.


"Meaningful results" are subjective to the hobbyist.

NO analyzer means NO results.

If I were designing a spectrum analyzer for the electronic instrument
market, I would shoot for at least meeting Hewlett-Packard Agilent
or Rhode&Schwarz specifications...R&D budget willing. That's a bit
steep for the hobbyist area.

The problem is that real incoming signals and the analyser's spurious
responses all look very much the same on the screen. When you can't
trust what the analyser says, it becomes very hard to understand what's
really going on.


Sigh. A spectrum analyzer, almost ALL of them, is one of the easier
instruments to characterize from the outside, using other instruments.
Frequency span, logarithmic linearity, passband of the final IF are all
relatively easy to determine from the outside.

So what if a spectrum analyzer isn't "perfect?" It is much, much
better than having NO spectrum analyzer.

The majority of spectrum analyzer input signal levels are most likely
to be UNDER -10 dbm. That input level is not - generally - going to
cause all kinds of "imperfections" in the viewed spectrum.

As with lots of beginner-level test equipment, it sometimes needs an
expert to understand it!


I disagree. There are any number of application notes free for the
downloading on the Internet, from Agilent they are copies of older
(two decades at least) FREE paper application notes. Agilent also
has free application notes on the basic building blocks within an
analyzer and much information on the characteristics of those blocks.

CATV tuners and low-level NE602 mixers are simply not the building
blocks for a high dynamic range receiver. The W7ZOI design uses much
more appropriate building blocks so its readouts are much more
trustworthy.


Yes, its possible to "conquer" the dreaded too-high-signal IM mountain
peaks with high-level mixers and higher-milliWatt first LOs. See Mini-
Circuits' catalog as one place for modules.

I haven't seen the "W7ZOI design" so I won't critique it at all. Having
used spectrum analyzers for about 4 decades, the high-input-level IM
bogeyman seldom goes "boo!" for most spectrum observation. That
includes transmitter output monitoring.

and can you quantify it?

Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


Have you priced the used spectrum analyzers lately? Do you expect
others to have ready access to "another" spectrum analyzer?

In checking my own little special-purpose IF strip Sweeper (a quasi-
spectrum-analyzer), I am fortunate to have a pair of H-P rotary step
attenuators (salvaged, checked for calibration by another) to determine
if the Log response curve of the Analog Devices chip is correct...rather
very basic stuff. Unfortunately, the accuracy of the external attenuator
is about the same as the AD accuracy. I'd love to have a Weinschel
Precision Bench Attenuator to use as a comparison, but don't, can't
afford one.

I do have a very good pair of H-P signal generators (very much previously
owned) which have been put in order by a good friend of mine. With the
help of an outboard lowpass filter (easy to make) which is also
characterised by response testing using a linear detector, I can guarantee
an RF signal with all harmonics down 60 dbc. The RF power output of
those generators is also separately characteriseable/calibrateable within
2 db of absolute level at the high-power output (0 dbm) all the way down
to -120 dbm, probably lower. The lower levels are determined by a
waveguide-below-cutoff internal attenuator which hardly ever jumps out of
calibration unless the mechanicals get goofy. The Weinschel attenuation
standard uses the same basic below-cutoff principle.

With all of the above (two generators, overlapping ranges) I can absolutely
guarantee a true "two-tone" testing setup for an analyzer to determine
what the 1 db or the 3 db IM values are of any receiver front end. So far,
I've never ever seen any cause for concern with any input level up to -10
dbm. Have I ever done any such? Of course, even checking out a used
(and rare) Tektronix spectrum analyzer plug-in on a borrow.

I have YET to encounter any receiver input that goes higher than -10 dbm
equivalent input with the one exception of being within two blocks of
local AM broadcast station KMPC pushing 50 KW into their antennas.
I'm sure there are all kinds of "exceptions" to that and I'm sure there will
be commentary coming back on that. :-)

I'm not going to get in about the relationship of sweep rate and final SA
IF resolution...which are VERY important in SA work, particularly in
relatively narrowband observations. Close-proximity signals can "hide"
if wide resolution IFs are in place...that "hiding" visible at input RF
levels
well below ANY intermodulation distortion level. The resolution aspect of
practical SA design is a separate matter but should not be forgotten..

When push comes to shove in all this, I'd say that SOME KIND of
spectrum analyzer is a LOT better than NONE. EOF.

Len Anderson
retired (from regular hours) electronic engineer person

Hans Summers July 23rd 03 08:53 AM


"John Miles" wrote in message
...
In article ,
says...

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you

think
it's superior to the poor man's spectrum analysers based on CATV tuners?

The
latter surely have greater frequency coverage. But in what ways are they
inferior and can you quantify it?


Apart from what Ian said, it's also really important to have a stable
LO. If you don't -- i.e., you're relying on an inadequately-stabilized
cable TV tuner -- you can only tell if a signal is present or absent.
You can't tell much about its stability and noise level, or look for
close-in IMD products. Narrow resolution bandwidths require stable LOs.

I haven't used a W7ZOI analyzer myself, but it ought to be at least an
order of magnitude more stable than any CATV implementation. It would
indeed be interesting to see a spec-for-spec comparison between the two.


The W7ZOI analyser uses a mini-circuits VCO. I couldn't find any stability
data on the minicricuits website, do you know of a source?
I suppose oscillator phase noise is also important. I'm interested in why a
minicircuits VCO should be an order of magnitude more stable than a CATV or
UHF TV tuner's VCO? I have a UHF tuner here (470-862MHz). The tuning voltage
(approx 1-25V) is stabilised by a simple zener diode arrangement. Even when
left on for hours tuned to a TV station, no re-tuning is necessary. As far
as I can tell there is no AFC employed.


Either way, they make great educational projects. :)


Agreed!

Hans G0UPL



Hans Summers July 23rd 03 08:53 AM


"John Miles" wrote in message
...
In article ,
says...

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


The W7ZOI project is very interesting. I'm interested in what ways you

think
it's superior to the poor man's spectrum analysers based on CATV tuners?

The
latter surely have greater frequency coverage. But in what ways are they
inferior and can you quantify it?


Apart from what Ian said, it's also really important to have a stable
LO. If you don't -- i.e., you're relying on an inadequately-stabilized
cable TV tuner -- you can only tell if a signal is present or absent.
You can't tell much about its stability and noise level, or look for
close-in IMD products. Narrow resolution bandwidths require stable LOs.

I haven't used a W7ZOI analyzer myself, but it ought to be at least an
order of magnitude more stable than any CATV implementation. It would
indeed be interesting to see a spec-for-spec comparison between the two.


The W7ZOI analyser uses a mini-circuits VCO. I couldn't find any stability
data on the minicricuits website, do you know of a source?
I suppose oscillator phase noise is also important. I'm interested in why a
minicircuits VCO should be an order of magnitude more stable than a CATV or
UHF TV tuner's VCO? I have a UHF tuner here (470-862MHz). The tuning voltage
(approx 1-25V) is stabilised by a simple zener diode arrangement. Even when
left on for hours tuned to a TV station, no re-tuning is necessary. As far
as I can tell there is no AFC employed.


Either way, they make great educational projects. :)


Agreed!

Hans G0UPL



Roy Lewallen July 23rd 03 10:14 AM

Oscillator phase noise will show up as noise sidebands on the signals
you're measuring. They'll limit your ability to use your spectrum
analyzer to judge the noise that's really coming from the signals. As a
very good and professional engineer who spent a number of years
designing some of the best commercial spectrum analyzers made, Wes most
certainly paid a great deal of attention to phase noise and dynamic
range, two of the most important potentially limiting factors of
spectrum analyzer performance.

Roy Lewallen, W7EL

Hans Summers wrote:

. . .
I suppose oscillator phase noise is also important. . .



Roy Lewallen July 23rd 03 10:14 AM

Oscillator phase noise will show up as noise sidebands on the signals
you're measuring. They'll limit your ability to use your spectrum
analyzer to judge the noise that's really coming from the signals. As a
very good and professional engineer who spent a number of years
designing some of the best commercial spectrum analyzers made, Wes most
certainly paid a great deal of attention to phase noise and dynamic
range, two of the most important potentially limiting factors of
spectrum analyzer performance.

Roy Lewallen, W7EL

Hans Summers wrote:

. . .
I suppose oscillator phase noise is also important. . .



Ian White, G3SEK July 23rd 03 11:00 AM

Avery Fineman wrote:
In article , "Ian White, G3SEK"
writes:

A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.


"Meaningful results" are subjective to the hobbyist.

I'm an amateur, not a professional, but have paid my dues in this area.
I have helped develop, and have built and used, two generations of HF (0
- 100MHz) spectrum analysers of the NE602 persuasion. Then a
basket-case Texscan 0-1GHz box came along which I rescued and used for
VHF work. That was followed by the HP-141 series analyser which I'm
currently using (and can now be bought for much less than the price of a
new rig). I also developed a 0-1.5GHz tracking generator for the 141
boxes. Through friends, I have some limited access to modern
professional equipment, and know how to use it.

My experience with the NE602 type is that it's great as a "fun"
analyser, but you can very quickly outgrow it. Yes, it will give you
general indications, like "Is that oscillator working?" or "Is that
final output stage generating harmonics?" Those indications even have
some numbers of MHz and dB attached.

NO analyzer means NO results.

Of course I'd rather have that much information than no analyser at all.
(Len, if you happen not to mention something that is completely obvious,
I still assume that you're completely aware of it. Kindly extend the
same courtesy to me.)


But once you have a "fun" analyser giving you basic indications, it
inevitably draws you into asking more searching questions, like "How
much of a harmonic problem do I really have?" That's where fun analysers
come unstuck, because you don't know how much of those indicated
harmonics are real, and how much is being generated in the analyser
itself.

An important practical crunch point for amateurs is "Does this
transmitter meet the FCC requirement for 60dB minimum harmonic
suppression?" Now you discover the big difference between 60-70dB
on-screen dynamic range, and 60-70dB *spurious-free* dynamic range. The
first is easy - the second is damned hard to guarantee in a HB design.

If you get to that point - and many people will - then you'll wish you'd
taken the extra trouble to build an analyser that you could trust a
little more. The NE602 type categorically will not hack that kind of
problem, because the equipment under test is probably much cleaner than
it is! The W7ZOI type may just do it, with care, and the same is true of
the 141 generation. Only the best modern analysers will ace the problem
without needing careful attention from the user.

The simple rule of thumb is:

1. If the performance of your test equipment is better - in whatever
ways are important for the measurement in hand - than the performance of
the equipment under test (EUT) then the results will be reliable enough
for amateur work.

2. If your test equipment is comparable with the EUT, you'll get useful
indications.

3. If your test equipment is worse than the EUT, what you're actually
testing is the testgear itself! You'll learn nothing useful about the
EUT, and may actually be misled.

So aim for zone 1, settle for zone 2 if you must, but stay out of zone
3.

and can you quantify it?

Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


Have you priced the used spectrum analyzers lately? Do you expect
others to have ready access to "another" spectrum analyzer?

That comment was mostly to make the point that the cleanest display is
the most real.

The absolute standard of comparison is the perfect spectrum analyser
with no spurious responses. That is an *idea* to which anyone has ready
access, any time.

Before I ever had a real spectrum analyser, I got a lot of good mileage
out of thinking "Now if I had a spectrum analyser, what would it
probably be showing me here?" That isn't empty dreaming - it's a highly
*practical* way of focusing your thinking on a problem in the
here-and-now.

When I built the first "fun" analyser (which had to wait until the
hardware collection had expanded to include a good oscilloscope) I found
it quite disappointing, because it still wasn't showing me reality. I
was still having to think "Now if I had a *good* spectrum analyser, what
would it probably be showing me here?"

Over the years, more and more of the mental testgear has been changed
into hardware, but the mental spectrum analyser still gets switched on
quite frequently - it has instant warmup and it also works very well in
the bath and, er, the other places where I do my best thinking!

Out in the workshop, the real hardware adds real-life numbers to the
ideas, and also checks that there isn't anything happening that I hadn't
thought of.



As with lots of beginner-level test equipment, it sometimes needs an
expert to understand it!


I disagree. There are any number of application notes free for the
downloading on the Internet, from Agilent they are copies of older
(two decades at least) FREE paper application notes. Agilent also
has free application notes on the basic building blocks within an
analyzer and much information on the characteristics of those blocks.

That's not the point. You are talking about the availability of
information, which is not in dispute. I am talking about understanding
and applying it.

By the time you've absorbed the available information - especially the
information about the *imperfections* of spectrum analysers, so you can
understand how much of what you see on-screen is real - you're not a
beginner any more. It will have been a useful learning experience... but
perhaps not the one you'd have chosen right then.

Being a beginner in any area is hard work. When you're ttrying to learn
what it's all about, the last thing you need is to have to fight poor
equipment as well. Musical instruments are very much the same -
so-called "beginner" instruments are actually quite hard work for anyone
to play; in contrast, a better-quality (read: expensive) instrument
feels almost like it's playing itself.

Unfortunately, budget reasons mean that beginners will almost always
have to learn on instruments (test or music) that are hard to use. We
have to accept that, but for heaven's sake let's not pretend to make a
virtue of it!

In this particular case, there does exist a very good, reliable,
second-level design (the W7ZOI). It's a little more expensive to build
than the entry-level stuff, but not significantly more complex. It's
very well designed, so while you're building it you'll learn some very
useful things from a top amateur (and former professional) RF designer.
It's also modular, so you can build it in stages, and upgrade various
parts as and when you want.


Bottom line: having played with the entry-level NE602 stuff myself, my
advice would be:

* If you only want a "fun" analyser, then go for it and have fun.

* But if you want the analyser as a tool to help you develop good radio
gear, go direct to the W7ZOI design.

For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ian White, G3SEK July 23rd 03 11:00 AM

Avery Fineman wrote:
In article , "Ian White, G3SEK"
writes:

A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.


"Meaningful results" are subjective to the hobbyist.

I'm an amateur, not a professional, but have paid my dues in this area.
I have helped develop, and have built and used, two generations of HF (0
- 100MHz) spectrum analysers of the NE602 persuasion. Then a
basket-case Texscan 0-1GHz box came along which I rescued and used for
VHF work. That was followed by the HP-141 series analyser which I'm
currently using (and can now be bought for much less than the price of a
new rig). I also developed a 0-1.5GHz tracking generator for the 141
boxes. Through friends, I have some limited access to modern
professional equipment, and know how to use it.

My experience with the NE602 type is that it's great as a "fun"
analyser, but you can very quickly outgrow it. Yes, it will give you
general indications, like "Is that oscillator working?" or "Is that
final output stage generating harmonics?" Those indications even have
some numbers of MHz and dB attached.

NO analyzer means NO results.

Of course I'd rather have that much information than no analyser at all.
(Len, if you happen not to mention something that is completely obvious,
I still assume that you're completely aware of it. Kindly extend the
same courtesy to me.)


But once you have a "fun" analyser giving you basic indications, it
inevitably draws you into asking more searching questions, like "How
much of a harmonic problem do I really have?" That's where fun analysers
come unstuck, because you don't know how much of those indicated
harmonics are real, and how much is being generated in the analyser
itself.

An important practical crunch point for amateurs is "Does this
transmitter meet the FCC requirement for 60dB minimum harmonic
suppression?" Now you discover the big difference between 60-70dB
on-screen dynamic range, and 60-70dB *spurious-free* dynamic range. The
first is easy - the second is damned hard to guarantee in a HB design.

If you get to that point - and many people will - then you'll wish you'd
taken the extra trouble to build an analyser that you could trust a
little more. The NE602 type categorically will not hack that kind of
problem, because the equipment under test is probably much cleaner than
it is! The W7ZOI type may just do it, with care, and the same is true of
the 141 generation. Only the best modern analysers will ace the problem
without needing careful attention from the user.

The simple rule of thumb is:

1. If the performance of your test equipment is better - in whatever
ways are important for the measurement in hand - than the performance of
the equipment under test (EUT) then the results will be reliable enough
for amateur work.

2. If your test equipment is comparable with the EUT, you'll get useful
indications.

3. If your test equipment is worse than the EUT, what you're actually
testing is the testgear itself! You'll learn nothing useful about the
EUT, and may actually be misled.

So aim for zone 1, settle for zone 2 if you must, but stay out of zone
3.

and can you quantify it?

Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


Have you priced the used spectrum analyzers lately? Do you expect
others to have ready access to "another" spectrum analyzer?

That comment was mostly to make the point that the cleanest display is
the most real.

The absolute standard of comparison is the perfect spectrum analyser
with no spurious responses. That is an *idea* to which anyone has ready
access, any time.

Before I ever had a real spectrum analyser, I got a lot of good mileage
out of thinking "Now if I had a spectrum analyser, what would it
probably be showing me here?" That isn't empty dreaming - it's a highly
*practical* way of focusing your thinking on a problem in the
here-and-now.

When I built the first "fun" analyser (which had to wait until the
hardware collection had expanded to include a good oscilloscope) I found
it quite disappointing, because it still wasn't showing me reality. I
was still having to think "Now if I had a *good* spectrum analyser, what
would it probably be showing me here?"

Over the years, more and more of the mental testgear has been changed
into hardware, but the mental spectrum analyser still gets switched on
quite frequently - it has instant warmup and it also works very well in
the bath and, er, the other places where I do my best thinking!

Out in the workshop, the real hardware adds real-life numbers to the
ideas, and also checks that there isn't anything happening that I hadn't
thought of.



As with lots of beginner-level test equipment, it sometimes needs an
expert to understand it!


I disagree. There are any number of application notes free for the
downloading on the Internet, from Agilent they are copies of older
(two decades at least) FREE paper application notes. Agilent also
has free application notes on the basic building blocks within an
analyzer and much information on the characteristics of those blocks.

That's not the point. You are talking about the availability of
information, which is not in dispute. I am talking about understanding
and applying it.

By the time you've absorbed the available information - especially the
information about the *imperfections* of spectrum analysers, so you can
understand how much of what you see on-screen is real - you're not a
beginner any more. It will have been a useful learning experience... but
perhaps not the one you'd have chosen right then.

Being a beginner in any area is hard work. When you're ttrying to learn
what it's all about, the last thing you need is to have to fight poor
equipment as well. Musical instruments are very much the same -
so-called "beginner" instruments are actually quite hard work for anyone
to play; in contrast, a better-quality (read: expensive) instrument
feels almost like it's playing itself.

Unfortunately, budget reasons mean that beginners will almost always
have to learn on instruments (test or music) that are hard to use. We
have to accept that, but for heaven's sake let's not pretend to make a
virtue of it!

In this particular case, there does exist a very good, reliable,
second-level design (the W7ZOI). It's a little more expensive to build
than the entry-level stuff, but not significantly more complex. It's
very well designed, so while you're building it you'll learn some very
useful things from a top amateur (and former professional) RF designer.
It's also modular, so you can build it in stages, and upgrade various
parts as and when you want.


Bottom line: having played with the entry-level NE602 stuff myself, my
advice would be:

* If you only want a "fun" analyser, then go for it and have fun.

* But if you want the analyser as a tool to help you develop good radio
gear, go direct to the W7ZOI design.

For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Hans Summers July 23rd 03 02:21 PM


"Ian White, G3SEK" wrote in message
...
Avery Fineman wrote:
In article , "Ian White, G3SEK"
writes:


[...]


But once you have a "fun" analyser giving you basic indications, it
inevitably draws you into asking more searching questions, like "How
much of a harmonic problem do I really have?" That's where fun analysers
come unstuck, because you don't know how much of those indicated
harmonics are real, and how much is being generated in the analyser
itself.


I think it does much better than just give general indications. It certainly
has opened my eyes to a whole new world inaccessible to me before having the
analyser. It's comparable to the change in my hobby life when I aquired my
first oscilloscope. You still enjoy the hobby with no oscilloscope, but when
you get one you feel like you'd been blind before, and can't imagine life
without it.

The other day I looked at the 39.5MHz IF in an old television tuned to a UK
TV station signal. I could see the video and sound subcarriers clearly
identifiable. Tuning the TV I could move the signals out of the Surface
Acoustic Wave (SAW) filter skirts and get a good idea of the shape of the
filter's response curve. Before I might have read about that stuff in
theory, now I can actually see it!

Under many cases it will be possible to identify any spurious signals
generated within the analyser itself. The input attenuator (in my case
0-63dB in 1dB steps) allows quite accurate measurement of the magnitude of
frequency components, and also allows reduction of strong signals. In many
cases this can be used to eliminate many of the spuri.

Or, if the signal being monitored is a VFO output for example, or another
variable frequency source, changing the frequency will often identify the
spurious signals. For example I might increase the VFO frequency, causing
the fundamental frequency peak to move left to right on the screen. If I see
some other peak move in the opposite direction, or if I see a peak moving
across the display very quickly, I know I've seen a spurious response.

Much of the spurious response problems come at the high end of the frequency
coverage range. For lower frequency work one could insert an additional
easily-constructed low pass filter and eliminate much of the problem.

So yes, no doubt the more effort you put in and the more complex the
spectrum analyser, the better the results obtainable. But even with a simple
analyser there's so much you can do.


An important practical crunch point for amateurs is "Does this
transmitter meet the FCC requirement for 60dB minimum harmonic
suppression?" Now you discover the big difference between 60-70dB
on-screen dynamic range, and 60-70dB *spurious-free* dynamic range. The
first is easy - the second is damned hard to guarantee in a HB design.


I could be wrong but I thought the FCC requirement was 40dB minimum harmonic
suppression, or 30dB for transmitters with output powers 5W or less? That's
well within the range of even a simple spectrum analyser. I doubt I'd have
any problem ensuring an HF QRP rig met FCC requirements with my analsyer.


If you get to that point - and many people will - then you'll wish you'd
taken the extra trouble to build an analyser that you could trust a
little more. The NE602 type categorically will not hack that kind of
problem, because the equipment under test is probably much cleaner than
it is! The W7ZOI type may just do it, with care, and the same is true of
the 141 generation. Only the best modern analysers will ace the problem
without needing careful attention from the user.


I'm already working on my Mk2 analyser. Not because I'm unhappy with the
measurements of the Mk1, but because I had so much fun with it, ending up
building it for its own sake, and not ready to stop having fun yet.


The simple rule of thumb is:

1. If the performance of your test equipment is better - in whatever
ways are important for the measurement in hand - than the performance of
the equipment under test (EUT) then the results will be reliable enough
for amateur work.

2. If your test equipment is comparable with the EUT, you'll get useful
indications.

3. If your test equipment is worse than the EUT, what you're actually
testing is the testgear itself! You'll learn nothing useful about the
EUT, and may actually be misled.

So aim for zone 1, settle for zone 2 if you must, but stay out of zone
3.


Not sure I agree completely - if the EUT is *supposed* to be in your zone 3,
but is not functioning properly, then even a simple spectrum analyser could
help you find the fault. It wouldn't help you make precise receiver
performance measurements on it when you corrected the fault, but would help
with diagnosis.

[...]


Bottom line: having played with the entry-level NE602 stuff myself, my
advice would be:

* If you only want a "fun" analyser, then go for it and have fun.

* But if you want the analyser as a tool to help you develop good radio
gear, go direct to the W7ZOI design.


Don't forget the W7ZOI analyser covers 0-70MHz only. You can double that
with a NE602 design. Nevertheless I liked the W7ZOI analyser a lot.


For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


Sounded interesting, but a google search as described turned up 0 results.
In fact a search for S57MV on its own got 0 results. Do you have any other
references?

73

Hans G0UPL




--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek




Hans Summers July 23rd 03 02:21 PM


"Ian White, G3SEK" wrote in message
...
Avery Fineman wrote:
In article , "Ian White, G3SEK"
writes:


[...]


But once you have a "fun" analyser giving you basic indications, it
inevitably draws you into asking more searching questions, like "How
much of a harmonic problem do I really have?" That's where fun analysers
come unstuck, because you don't know how much of those indicated
harmonics are real, and how much is being generated in the analyser
itself.


I think it does much better than just give general indications. It certainly
has opened my eyes to a whole new world inaccessible to me before having the
analyser. It's comparable to the change in my hobby life when I aquired my
first oscilloscope. You still enjoy the hobby with no oscilloscope, but when
you get one you feel like you'd been blind before, and can't imagine life
without it.

The other day I looked at the 39.5MHz IF in an old television tuned to a UK
TV station signal. I could see the video and sound subcarriers clearly
identifiable. Tuning the TV I could move the signals out of the Surface
Acoustic Wave (SAW) filter skirts and get a good idea of the shape of the
filter's response curve. Before I might have read about that stuff in
theory, now I can actually see it!

Under many cases it will be possible to identify any spurious signals
generated within the analyser itself. The input attenuator (in my case
0-63dB in 1dB steps) allows quite accurate measurement of the magnitude of
frequency components, and also allows reduction of strong signals. In many
cases this can be used to eliminate many of the spuri.

Or, if the signal being monitored is a VFO output for example, or another
variable frequency source, changing the frequency will often identify the
spurious signals. For example I might increase the VFO frequency, causing
the fundamental frequency peak to move left to right on the screen. If I see
some other peak move in the opposite direction, or if I see a peak moving
across the display very quickly, I know I've seen a spurious response.

Much of the spurious response problems come at the high end of the frequency
coverage range. For lower frequency work one could insert an additional
easily-constructed low pass filter and eliminate much of the problem.

So yes, no doubt the more effort you put in and the more complex the
spectrum analyser, the better the results obtainable. But even with a simple
analyser there's so much you can do.


An important practical crunch point for amateurs is "Does this
transmitter meet the FCC requirement for 60dB minimum harmonic
suppression?" Now you discover the big difference between 60-70dB
on-screen dynamic range, and 60-70dB *spurious-free* dynamic range. The
first is easy - the second is damned hard to guarantee in a HB design.


I could be wrong but I thought the FCC requirement was 40dB minimum harmonic
suppression, or 30dB for transmitters with output powers 5W or less? That's
well within the range of even a simple spectrum analyser. I doubt I'd have
any problem ensuring an HF QRP rig met FCC requirements with my analsyer.


If you get to that point - and many people will - then you'll wish you'd
taken the extra trouble to build an analyser that you could trust a
little more. The NE602 type categorically will not hack that kind of
problem, because the equipment under test is probably much cleaner than
it is! The W7ZOI type may just do it, with care, and the same is true of
the 141 generation. Only the best modern analysers will ace the problem
without needing careful attention from the user.


I'm already working on my Mk2 analyser. Not because I'm unhappy with the
measurements of the Mk1, but because I had so much fun with it, ending up
building it for its own sake, and not ready to stop having fun yet.


The simple rule of thumb is:

1. If the performance of your test equipment is better - in whatever
ways are important for the measurement in hand - than the performance of
the equipment under test (EUT) then the results will be reliable enough
for amateur work.

2. If your test equipment is comparable with the EUT, you'll get useful
indications.

3. If your test equipment is worse than the EUT, what you're actually
testing is the testgear itself! You'll learn nothing useful about the
EUT, and may actually be misled.

So aim for zone 1, settle for zone 2 if you must, but stay out of zone
3.


Not sure I agree completely - if the EUT is *supposed* to be in your zone 3,
but is not functioning properly, then even a simple spectrum analyser could
help you find the fault. It wouldn't help you make precise receiver
performance measurements on it when you corrected the fault, but would help
with diagnosis.

[...]


Bottom line: having played with the entry-level NE602 stuff myself, my
advice would be:

* If you only want a "fun" analyser, then go for it and have fun.

* But if you want the analyser as a tool to help you develop good radio
gear, go direct to the W7ZOI design.


Don't forget the W7ZOI analyser covers 0-70MHz only. You can double that
with a NE602 design. Nevertheless I liked the W7ZOI analyser a lot.


For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


Sounded interesting, but a google search as described turned up 0 results.
In fact a search for S57MV on its own got 0 results. Do you have any other
references?

73

Hans G0UPL




--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek




Mike Andrews July 23rd 03 03:45 PM

Ian White, G3SEK wrote:

For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


I just tried the suggested Google search, and came up dry -- using
both spellings: analyzer/analyser. Since I cut-and-pasted "S57MV"
from your post, I doubt that it was a spelling error.

Any suggestions?

--
I don't need speed-reading,
I need speed-bookcase-building.
(with thanks to Nancy Lebovitz)

Mike Andrews July 23rd 03 03:45 PM

Ian White, G3SEK wrote:

For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


I just tried the suggested Google search, and came up dry -- using
both spellings: analyzer/analyser. Since I cut-and-pasted "S57MV"
from your post, I doubt that it was a spelling error.

Any suggestions?

--
I don't need speed-reading,
I need speed-bookcase-building.
(with thanks to Nancy Lebovitz)

Ian White, G3SEK July 23rd 03 04:23 PM

Hans Summers wrote:

[snipped much on which we either agree, or can amicably agree to differ]

Certainly, build something rather than nothing - as Hans says, it will
really open your eyes!


For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


Sounded interesting, but a google search as described turned up 0
results. In fact a search for S57MV on its own got 0 results. Do you
have any other references?

Sorry, it was S53MV. A lot of the older information has disappeared off
the web, and is now only to be found on the site of VHF Communications
magazine where SM3MV's original article appeared.

http://www.vhfcomm.co.uk/articles.htm

Since the article is said to be too big for the web site (and the web
articles have no diagrams anyway) it seems that you cannot learn
anything useful about this excellent project without buying a back-issue
of the magazine :-(


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ian White, G3SEK July 23rd 03 04:23 PM

Hans Summers wrote:

[snipped much on which we either agree, or can amicably agree to differ]

Certainly, build something rather than nothing - as Hans says, it will
really open your eyes!


For a VHF/UHF HB design - which is obviously going to be a lot more
complex, and really is an advanced project - search Google for: "S57MV
spectrum analyser" (without the quotes, and also look for the American
"analyzer" spelling).


Sounded interesting, but a google search as described turned up 0
results. In fact a search for S57MV on its own got 0 results. Do you
have any other references?

Sorry, it was S53MV. A lot of the older information has disappeared off
the web, and is now only to be found on the site of VHF Communications
magazine where SM3MV's original article appeared.

http://www.vhfcomm.co.uk/articles.htm

Since the article is said to be too big for the web site (and the web
articles have no diagrams anyway) it seems that you cannot learn
anything useful about this excellent project without buying a back-issue
of the magazine :-(


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Avery Fineman July 24th 03 05:22 AM

In article , "Ian White, G3SEK"
writes:

Avery Fineman wrote:
In article , "Ian White, G3SEK"
writes:

A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.


"Meaningful results" are subjective to the hobbyist.

I'm an amateur, not a professional, but have paid my dues in this area.


Okay. Then allow me to state that I've been a professional in radio
and electronics for 51 years AND an electronics hobbyist in my
free time for longer. I've not "paid any dues" in the latter area except
a lot of hours spent having fun in my workshop..

My experience with the NE602 type is that it's great as a "fun"
analyser, but you can very quickly outgrow it. Yes, it will give you
general indications, like "Is that oscillator working?" or "Is that
final output stage generating harmonics?" Those indications even have
some numbers of MHz and dB attached.


? What is wrong with that?

An NE602 or SA602 is just a means to an end. It's a nice little IC
that allows some balanced mixing AND as the active device for the
local oscillator. A single IC, dual function. Used within its limitations
it is AS ACCURATE AS ANY OTHER DEVICE.

NO analyzer means NO results.

Of course I'd rather have that much information than no analyser at all.
(Len, if you happen not to mention something that is completely obvious,
I still assume that you're completely aware of it. Kindly extend the
same courtesy to me.)


I have NO idea of what is "completely obvious" to anyone. Everyone's
mileage varies.

But once you have a "fun" analyser giving you basic indications, it
inevitably draws you into asking more searching questions, like "How
much of a harmonic problem do I really have?" That's where fun analysers
come unstuck, because you don't know how much of those indicated
harmonics are real, and how much is being generated in the analyser
itself.


Let's not lump all the "non-pro" analyzers into the "fun-toy" category,
okay?

Sorry, but I can quickly categorize/calibrate/check ANY analyzer as
to whether or not whatever it shows is "real" or internal. There's lots
of written information available on how to do that...and a bit of thinking
will reveal the very same thing.

An important practical crunch point for amateurs is "Does this
transmitter meet the FCC requirement for 60dB minimum harmonic
suppression?" Now you discover the big difference between 60-70dB
on-screen dynamic range, and 60-70dB *spurious-free* dynamic range. The
first is easy - the second is damned hard to guarantee in a HB design.


Sorry, you've drifted outside of specific spectrum analyzer use. The
harmonic content of ALL transmitters can be measured WITHOUT
any spectrum analyzer, as accurately (in most cases moreso) as with
an analyzer. A spectrum analyzer is much much faster in that
application, but harmonic content measurement is not dependent on
its use.

Good operation and good specifications in homebrew designs are as
good as the designer, as good as the other equipment for calibration
and characterisation that is used. It's all together. It's only "damned
hard to guarantee" if there is nothing available to ascertain operation
and calibration. That can exist equally well for an HP 141 plug-in or
one that you term a "fun" NE602.

If you get to that point - and many people will - then you'll wish you'd
taken the extra trouble to build an analyser that you could trust a
little more. The NE602 type categorically will not hack that kind of
problem, because the equipment under test is probably much cleaner than
it is!


Good grief! There's plenty of instances in metrology where actual
measurements are done to a higher level than what each piece of
test equipment can do. Time and frequency measurement is a good
area for examples in that, other areas' explanations will take more
time to describe than I have at the moment.

EVERY single piece of test equipment MUST be used within its
limitations. That INCLUDES your "HP 141" racks, Anritsu analyzers,
etc., and whatever else is there.

The W7ZOI type may just do it, with care, and the same is true of
the 141 generation. Only the best modern analysers will ace the problem
without needing careful attention from the user.


Nonsense. Each and every "user" had damn well pay close attention
to using whatever they have within its equipment's limitations. That
holds true for the best of Rhode & Schwarz wares AND for the "fun"
SA602/NE602 analyzers.


Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


Have you priced the used spectrum analyzers lately? Do you expect
others to have ready access to "another" spectrum analyzer?

That comment was mostly to make the point that the cleanest display is
the most real.


You're going to have to explain that better..."clean" is highly subjective
and subjective judgement in any metrology effort is a no-no.

The absolute standard of comparison is the perfect spectrum analyser
with no spurious responses.


Okay, show me one. They must be in storage with bottles of the
"universal solvent" and other fine ideas...


When I built the first "fun" analyser (which had to wait until the
hardware collection had expanded to include a good oscilloscope) I found
it quite disappointing, because it still wasn't showing me reality. I
was still having to think "Now if I had a *good* spectrum analyser, what
would it probably be showing me here?"


That's nice. But you are drifting towards extreme categorization of
equipment. Simple, low parts count home projects are "fun" (in your
terms, like toys or something for recreation. The only "GOOD" gear
is semi-pro, expensive, etc., etc., etc.


Out in the workshop, the real hardware adds real-life numbers to the
ideas, and also checks that there isn't anything happening that I hadn't
thought of.


In MY workshop, nearly everything I do and use is pure FUN. If I use
them within their limitations, then they give me REAL numbers as
valid as anything I use from a small pro lab's $400K capital collection.


In this particular case, there does exist a very good, reliable,
second-level design (the W7ZOI). It's a little more expensive to build
than the entry-level stuff, but not significantly more complex. It's
very well designed, so while you're building it you'll learn some very
useful things from a top amateur (and former professional) RF designer.
It's also modular, so you can build it in stages, and upgrade various
parts as and when you want.

Bottom line: having played with the entry-level NE602 stuff myself, my
advice would be:

* If you only want a "fun" analyser, then go for it and have fun.

* But if you want the analyser as a tool to help you develop good radio
gear, go direct to the W7ZOI design.


So...bottom line is that spectrum analyzers with NE602s in them are
kiddie toys useable only for entertainment and recreation?!?

Not a good characterization, that. Used within its limitations, the
"kiddie" instrument is as accurate as anything else. Input level
displayed linearity is a direct function of the successive detection
logarithmic chip used in the back end...has very little to do with the
front end. Resolution is again a back-end concern and is a direct
function of the filtering of the final IF in the analyzer...and the sweep
rate and sweep span (all related). If you want linearity in the
horizontal as to frequency, then you have to pay a lot of attention to
VCO (or equivalent) control and that has little to do with messing
about with the front end mixer.

The front end of any spectrum analyzer is the place where your
spurious responses are generated, if any at all. If you are going for
the very best in higher-level inputs then you absolutely need a high-
IM-rated mixer, which also probably needs a high-level LO. Both of
those cost a great deal of money...and the higher input level free of
spurious responses may or may not be worth it. It may not be
worth it when one of those "fun" analyzers don't exhibit any false
signals or spurii below a specific input level.

Len Anderson
retired (from regular hours) electronic engineer person
formerly an Associate Editor with HAM RADIO Magazine

PS: I once or twice used an HP 141. It always had "ordinary"
oscilloscope plug-ins in it to make it overall an oscilloscope. Shrug.

Avery Fineman July 24th 03 05:22 AM

In article , "Ian White, G3SEK"
writes:

Avery Fineman wrote:
In article , "Ian White, G3SEK"
writes:

A spectrum analyser is simply a frequency-swept receiver with a
dB-scaled output to a screen. To give meaningful results, that receiver
must have a very high dynamic range with very low spurious responses.


"Meaningful results" are subjective to the hobbyist.

I'm an amateur, not a professional, but have paid my dues in this area.


Okay. Then allow me to state that I've been a professional in radio
and electronics for 51 years AND an electronics hobbyist in my
free time for longer. I've not "paid any dues" in the latter area except
a lot of hours spent having fun in my workshop..

My experience with the NE602 type is that it's great as a "fun"
analyser, but you can very quickly outgrow it. Yes, it will give you
general indications, like "Is that oscillator working?" or "Is that
final output stage generating harmonics?" Those indications even have
some numbers of MHz and dB attached.


? What is wrong with that?

An NE602 or SA602 is just a means to an end. It's a nice little IC
that allows some balanced mixing AND as the active device for the
local oscillator. A single IC, dual function. Used within its limitations
it is AS ACCURATE AS ANY OTHER DEVICE.

NO analyzer means NO results.

Of course I'd rather have that much information than no analyser at all.
(Len, if you happen not to mention something that is completely obvious,
I still assume that you're completely aware of it. Kindly extend the
same courtesy to me.)


I have NO idea of what is "completely obvious" to anyone. Everyone's
mileage varies.

But once you have a "fun" analyser giving you basic indications, it
inevitably draws you into asking more searching questions, like "How
much of a harmonic problem do I really have?" That's where fun analysers
come unstuck, because you don't know how much of those indicated
harmonics are real, and how much is being generated in the analyser
itself.


Let's not lump all the "non-pro" analyzers into the "fun-toy" category,
okay?

Sorry, but I can quickly categorize/calibrate/check ANY analyzer as
to whether or not whatever it shows is "real" or internal. There's lots
of written information available on how to do that...and a bit of thinking
will reveal the very same thing.

An important practical crunch point for amateurs is "Does this
transmitter meet the FCC requirement for 60dB minimum harmonic
suppression?" Now you discover the big difference between 60-70dB
on-screen dynamic range, and 60-70dB *spurious-free* dynamic range. The
first is easy - the second is damned hard to guarantee in a HB design.


Sorry, you've drifted outside of specific spectrum analyzer use. The
harmonic content of ALL transmitters can be measured WITHOUT
any spectrum analyzer, as accurately (in most cases moreso) as with
an analyzer. A spectrum analyzer is much much faster in that
application, but harmonic content measurement is not dependent on
its use.

Good operation and good specifications in homebrew designs are as
good as the designer, as good as the other equipment for calibration
and characterisation that is used. It's all together. It's only "damned
hard to guarantee" if there is nothing available to ascertain operation
and calibration. That can exist equally well for an HP 141 plug-in or
one that you term a "fun" NE602.

If you get to that point - and many people will - then you'll wish you'd
taken the extra trouble to build an analyser that you could trust a
little more. The NE602 type categorically will not hack that kind of
problem, because the equipment under test is probably much cleaner than
it is!


Good grief! There's plenty of instances in metrology where actual
measurements are done to a higher level than what each piece of
test equipment can do. Time and frequency measurement is a good
area for examples in that, other areas' explanations will take more
time to describe than I have at the moment.

EVERY single piece of test equipment MUST be used within its
limitations. That INCLUDES your "HP 141" racks, Anritsu analyzers,
etc., and whatever else is there.

The W7ZOI type may just do it, with care, and the same is true of
the 141 generation. Only the best modern analysers will ace the problem
without needing careful attention from the user.


Nonsense. Each and every "user" had damn well pay close attention
to using whatever they have within its equipment's limitations. That
holds true for the best of Rhode & Schwarz wares AND for the "fun"
SA602/NE602 analyzers.


Very easily, in the same ways as you test a receiver for strong-signal
handling.... but most graphically by looking at the same spectra with
two analysers side-by-side. The one showing fewest signals is the one
you can rely on most.


Have you priced the used spectrum analyzers lately? Do you expect
others to have ready access to "another" spectrum analyzer?

That comment was mostly to make the point that the cleanest display is
the most real.


You're going to have to explain that better..."clean" is highly subjective
and subjective judgement in any metrology effort is a no-no.

The absolute standard of comparison is the perfect spectrum analyser
with no spurious responses.


Okay, show me one. They must be in storage with bottles of the
"universal solvent" and other fine ideas...


When I built the first "fun" analyser (which had to wait until the
hardware collection had expanded to include a good oscilloscope) I found
it quite disappointing, because it still wasn't showing me reality. I
was still having to think "Now if I had a *good* spectrum analyser, what
would it probably be showing me here?"


That's nice. But you are drifting towards extreme categorization of
equipment. Simple, low parts count home projects are "fun" (in your
terms, like toys or something for recreation. The only "GOOD" gear
is semi-pro, expensive, etc., etc., etc.


Out in the workshop, the real hardware adds real-life numbers to the
ideas, and also checks that there isn't anything happening that I hadn't
thought of.


In MY workshop, nearly everything I do and use is pure FUN. If I use
them within their limitations, then they give me REAL numbers as
valid as anything I use from a small pro lab's $400K capital collection.


In this particular case, there does exist a very good, reliable,
second-level design (the W7ZOI). It's a little more expensive to build
than the entry-level stuff, but not significantly more complex. It's
very well designed, so while you're building it you'll learn some very
useful things from a top amateur (and former professional) RF designer.
It's also modular, so you can build it in stages, and upgrade various
parts as and when you want.

Bottom line: having played with the entry-level NE602 stuff myself, my
advice would be:

* If you only want a "fun" analyser, then go for it and have fun.

* But if you want the analyser as a tool to help you develop good radio
gear, go direct to the W7ZOI design.


So...bottom line is that spectrum analyzers with NE602s in them are
kiddie toys useable only for entertainment and recreation?!?

Not a good characterization, that. Used within its limitations, the
"kiddie" instrument is as accurate as anything else. Input level
displayed linearity is a direct function of the successive detection
logarithmic chip used in the back end...has very little to do with the
front end. Resolution is again a back-end concern and is a direct
function of the filtering of the final IF in the analyzer...and the sweep
rate and sweep span (all related). If you want linearity in the
horizontal as to frequency, then you have to pay a lot of attention to
VCO (or equivalent) control and that has little to do with messing
about with the front end mixer.

The front end of any spectrum analyzer is the place where your
spurious responses are generated, if any at all. If you are going for
the very best in higher-level inputs then you absolutely need a high-
IM-rated mixer, which also probably needs a high-level LO. Both of
those cost a great deal of money...and the higher input level free of
spurious responses may or may not be worth it. It may not be
worth it when one of those "fun" analyzers don't exhibit any false
signals or spurii below a specific input level.

Len Anderson
retired (from regular hours) electronic engineer person
formerly an Associate Editor with HAM RADIO Magazine

PS: I once or twice used an HP 141. It always had "ordinary"
oscilloscope plug-ins in it to make it overall an oscilloscope. Shrug.

Mario July 25th 03 06:30 PM

John Miles wrote in message ...
In article ,
says...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


Here is an updated version of the W7ZOI spectrum analyzer on the same site:

http://www.qsl.net/n9zia/spec/index.html

Mario July 25th 03 06:30 PM

John Miles wrote in message ...
In article ,
says...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


Here is an updated version of the W7ZOI spectrum analyzer on the same site:

http://www.qsl.net/n9zia/spec/index.html

Michael Black July 25th 03 06:43 PM

Mario ) writes:
John Miles wrote in message ...
In article ,
says...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


Here is an updated version of the W7ZOI spectrum analyzer on the same site:

http://www.qsl.net/n9zia/spec/index.html


For that matter, Wes Hayward has his own webpage, and he has some material
related to the project at:
http://users.easystreet.com/w7zoi/SA.html
According to that page, one can download the original articles from
the ARRL website, in pdf format, but doing a search over there, I don't
get a hit on the articles.

I don't see it in the 2001 Handbook (the only recent one I have), but
perhaps it's in that new Hayward book, "Experimental Methods in RF Design"
but I've yet to order my copy.

And of course, Kanga, http://www.bright.net/~kanga/kanga
has boards for the project, and they have some additional information
on their website.

Michael VE2BVW


Michael Black July 25th 03 06:43 PM

Mario ) writes:
John Miles wrote in message ...
In article ,
says...
hi, where can i find practical high fre spectrum analyser circuit?
thanks


The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.


Here is an updated version of the W7ZOI spectrum analyzer on the same site:

http://www.qsl.net/n9zia/spec/index.html


For that matter, Wes Hayward has his own webpage, and he has some material
related to the project at:
http://users.easystreet.com/w7zoi/SA.html
According to that page, one can download the original articles from
the ARRL website, in pdf format, but doing a search over there, I don't
get a hit on the articles.

I don't see it in the 2001 Handbook (the only recent one I have), but
perhaps it's in that new Hayward book, "Experimental Methods in RF Design"
but I've yet to order my copy.

And of course, Kanga, http://www.bright.net/~kanga/kanga
has boards for the project, and they have some additional information
on their website.

Michael VE2BVW


John Miles July 26th 03 06:33 PM

In article ,
says...

Here is an updated version of the W7ZOI spectrum analyzer on the same site:

http://www.qsl.net/n9zia/spec/index.html


Mmm. Postscript documents. Real useful. NOT... :(

Sounds like an interesting variation on the project, but without
documentation in a standard, open format, his audience is going to be
limited.

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------


John Miles July 26th 03 06:33 PM

In article ,
says...

Here is an updated version of the W7ZOI spectrum analyzer on the same site:

http://www.qsl.net/n9zia/spec/index.html


Mmm. Postscript documents. Real useful. NOT... :(

Sounds like an interesting variation on the project, but without
documentation in a standard, open format, his audience is going to be
limited.

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------


Bob Headrick July 27th 03 12:19 AM


"John Miles" wrote in message
...
In article ,
says...

Here is an updated version of the W7ZOI spectrum analyzer on the same

site:

http://www.qsl.net/n9zia/spec/index.html


Mmm. Postscript documents. Real useful. NOT... :(

Sounds like an interesting variation on the project, but without
documentation in a standard, open format, his audience is going to be
limited.


Postscript is about as open and standard a format as you will find.
http://www.cs.wisc.edu/~ghost/ has free ghostscript viewers for most popular
platforms (windows, Linux, Mac, OS/2, VMS, etc).

- 73 Bob W7OV



Bob Headrick July 27th 03 12:19 AM


"John Miles" wrote in message
...
In article ,
says...

Here is an updated version of the W7ZOI spectrum analyzer on the same

site:

http://www.qsl.net/n9zia/spec/index.html


Mmm. Postscript documents. Real useful. NOT... :(

Sounds like an interesting variation on the project, but without
documentation in a standard, open format, his audience is going to be
limited.


Postscript is about as open and standard a format as you will find.
http://www.cs.wisc.edu/~ghost/ has free ghostscript viewers for most popular
platforms (windows, Linux, Mac, OS/2, VMS, etc).

- 73 Bob W7OV



Richard Hosking July 27th 03 01:29 PM

I have a HP 141 series device which is reasonable from the point of view of
strong signal handling.
It is surprisingly easy to produce intermodulation effects at levels lower
than you would expect.
A "forest" of signals at -20 dBm will produce IM effects by the additive
effect of all their amplitudes.(you could easily get this from a 40M dipole
at night for example)
In fact, my friend Rod Green has done an article for QEX on a "figure of
merit" device to test receiver strong signal handling which consists of a
"comb generator" with harmonics every 20 KHz, and a bandpass filter covering
the band of interest - say 7.0 to 7.2 MHz. At a comb level of -20dBm most
receivers will be overwhelmed.

Richard

If I were designing a spectrum analyzer for the electronic instrument
market, I would shoot for at least meeting Hewlett-Packard Agilent
or Rhode&Schwarz specifications...R&D budget willing. That's a bit
steep for the hobbyist area.

The problem is that real incoming signals and the analyser's spurious
responses all look very much the same on the screen. When you can't
trust what the analyser says, it becomes very hard to understand what's
really going on.


Sigh. A spectrum analyzer, almost ALL of them, is one of the easier
instruments to characterize from the outside, using other instruments.
Frequency span, logarithmic linearity, passband of the final IF are all
relatively easy to determine from the outside.


Len Anderson
retired (from regular hours) electronic engineer person





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