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

"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

"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

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
------------------------------------------------------

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
------------------------------------------------------

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

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

"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

"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

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