Keep in mind that anything much newer than the 141T will have custom
parts and processors.
This makes the instrument smaller and more versatile, but, less repairable.
The 141T is a workhorse.

I would not trade mine for any number of the processor controlled analyzers.
Having a nice clean analog display is nice and you do not have to
worry about did I get an accurate display of what I am looking at or
did what I am looking for occur between sample on the digital display.

I hope you find what you are looking for. It is hard to beat the 141T
for a spectrum analyzer.

73
Glenn
WB4UIV

At 11:06 PM 10/30/2009, you wrote:

At Microwave Update last week, Hangar 18 Surplus (
http://www.hangar18surplus.com ) had a really clean looking, late-production
Tek 497P on their table for $2500.  That would be a really good match for
what you're asking for.  I was surprised it didn't sell -- you might call
them and see if they still have it.

I don't think you'll miss the 141T if you get one of these.

-- john, KE5FX

On Fri, Oct 30, 2009 at 11:39:37PM -0400, Glenn Little WB4UIV wrote:

I disagree.   Modern analyzers have a LOT of features the 141T

family lacks - starting I guess with full frequency synthesis for near
time nuts level frequency accuracy (most all take external 10 MHz from a
standard and are fully coherent with this).    This makes a REAL
difference if you are interested in observing and analyzing unknown
signals... and allows the analyzer to also serve as a (microwave)
frequency counter.  If you are observing a crowded part of the
spectrum, having say 5 MHz or so frequency accuracy (typical of
unsynthesized instruments at VHF and above)  doesn't cut it AT ALL...
gets to be completely impossible to reliably identify a particular weak
signal or spur with 50 others nearby.

And frequency synthesis also allows precise keypad entry of a

frequency of interest (or via GPIB or other remote control)... try that
on an analog only crank the dial instrument.  At best you will do a LOT
of dial cranking...

Another feature less pre-Cambrian analyzers have is markers...

allowing accurate measurement of level and frequency at a particular
point on the screen, and often differential measurement too (eg so many
db down). Most instruments with markers will also do auto-peak search so
you can find the next left or right peak and read its frequency and
level with one key press.  And usually the marker readout of frequency
and level is significantly more accurate and higher resolution than the
display can be read easily... and often more than one marker is allowed
on screen at once.

And yet another feature modern analyzers have is digital display

memory - which makes it usefully possible to make slow narrow band
measurements with say 100 Hz or  30 Hz bandwidths.  Really antique
analyzers had display storage tubes or similar arrangements as options,
but all even slightly modern ones have fully integrated digital storage
and displays.

And yet another feature that present in all modern instruments

is peak hold, and usually also valley hold... allowing one to look over
time for elusive signals that appear only momentarily, or see how strong
or weak the noise or some signal got in a particular time interval.

Most modern instruments also include extensive self check and

auto-calibration firmware which can compensate for drift and aging of
the various analog circuits and handle temperature and other
environmental changes much better than older instruments without it.

And modern instruments have as at least as an option (usually

installed) some form of remote control allowing software to access the
measured data and control the analyzer - making possible all kinds of SW
applications that process measurements into more useful forms and
perform various corrections. GPIB is very common here.

Another feature absent in 141T era analyzers is plotting or

printing the screen via a printer of some kind (or these days a printer
emulation program such as the excellent ones John Miles provides).
This allows capture of a  fully annotated screen image (these days as a
.png file)...

Really modern instruments (last 10 years or so) also often have

FFT processing for fast narrow band analysis and modulation domain
analysis including digital demodulation and constellation and error
vector displays.

And many more recent instruments have built in firmware

measurements of things like occupied bandwidth and noise power per root
Hz... this all can be done with an attached laptop, but it is nice to
have it integrated and available with a button press.

It is true, of course, that the more recent the instrument the

more likely it is to have at least some proprietary parts that are
probably unobtanium by the time the instrument hits the affordable
surplus market.  And unfortunately many really modern instruments do
not have easily obtained schematics and chip level documentation
available - this alas being true of most T+M gear made recently, not
just SAs.  But lots of instruments with all the features I have
described above that date from the late 80s through 2000 or so are
readily available in your under $3K price range now and ARE documented
by available service manuals and schematics.

--
Dave Emery N1PRE/AE, die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

I bought from Naptech a very clean HP8566B for $2200. I am very happy with
it.

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of John Miles
Sent: Friday, October 30, 2009 11:06 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] OT: Spectrum Analyzer

At Microwave Update last week, Hangar 18 Surplus (
http://www.hangar18surplus.com ) had a really clean looking, late-production
Tek 497P on their table for $2500.  That would be a really good match for
what you're asking for.  I was surprised it didn't sell -- you might call
them and see if they still have it.

I don't think you'll miss the 141T if you get one of these.

-- john, KE5FX

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The HP8569 is a good moderate-price choice that goes up to 18GHz.  It's
new enough to have digital display, so you can do trace math like
normalization, and dump plots via GPIB.  However, you cannot set
commands via GPIB.

The LO is stabilized (not synthesized) so frequency accuracy isn't too bad.

One weakness is that the rotary switches have plastic components that
get brittle with age.  Pieces can snap off leaving some switch positions
non-functional.  However, these can be repaired with care.

I haven't priced one recently, but I would think you could find one in
the $2K range or possibly lower.

John

Brent Gordon said the following on 10/30/2009 11:06 PM:

On 10/31/09 5:26 AM, "John Ackermann N8UR" jra@febo.com wrote:

Since you're thinking about building something, how about somewhere in
between a piece of lab gear and total homebrew.  The PC controlled receivers
like the Icom PCR1000 work pretty well as a spectrum analyzer and tune DC to
1 GHz-ish.  So a good LO and a mixer in front of this might be a way to go.
Yeah, you won't get the whole 3 GHz in one span.  For smaller resolution BW
than the narrowest filter in the PCR1000, you can run the audio output with
the receiver in SSB mode into a spectrogram program.

Instead of the PCR1000, you could use one of the SDR widgets out now (like a
softrock), but that's going to be a LOT more homebrew.

The LO for mixing down from microwaves could be done a bunch of ways.
There's PLL eval boards which have a USB interface, for instance.

Since Jim opened the door, I should mention that one of the projects
underway for the High Performance SDR group (http://www.openhpsdr.org)
is "Cyclops" which works with the existing HPSDR Mercury receiver board
to provide a DC - 1 GHz spectrum analyzer and tracking generator.  Not
sure when it will become available; alpha boards are currently being
built and tested.  I am guessing that the system will be <$1500.

More details at http://openhpsdr.org/wiki/index.php?title=CYCLOPS.

John

Lux, Jim (337C) said the following on 10/31/2009 08:37 AM:

Hi Brent:

Spectrum analyzers can be used in different ways.  For example if you know
there's a signal and want to characterize it.  The other case is where you're
looking for some unknown signal that may be (or may not be present) down near
the noise threshold.

The first case is straight forward and any of the modern analyzers will do a
good job.  In the search case analyzers like the HP 70,000 series or the 4395A,
4396A/B can search orders of magnitude faster than conventional units.
http://www.prc68.com/I/4395A.shtml

Note that the 4395A uses a 12 MHz wide analog IF feeding a fast DSP based
receiver.  This allows things like a real 1 Hz IF bandwidth and also allows
real power [SQRT(I^2 + Q^2) detection].  All analog SAs use peak detection
since they have no way of detecting power.

Have Fun,

Brooke Clarke
http://www.prc68.com

Brent Gordon wrote:

Another major difference between the older (sweeping) analyzers and the more modern ones (FFT) is that the sweep type analyzers only look at one particular frequency once per sweep, and for a short time, while the fft types pretty much look at the entire span continuously. That makes the fft type much more capable of identifying low duty cycle transmitters. If the signals you are interested in are CW, it will not make much difference, but that is not always the case.

Didier KO4BB

------------------------ Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Brooke Clarke brooke@pacific.net
Date: Sat, 31 Oct 2009 13:03:29
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Subject: Re: [time-nuts] OT:  Spectrum Analyzer

Hi Brent:

Spectrum analyzers can be used in different ways.  For example if you know
there's a signal and want to characterize it.  The other case is where you're
looking for some unknown signal that may be (or may not be present) down near
the noise threshold.

The first case is straight forward and any of the modern analyzers will do a
good job.  In the search case analyzers like the HP 70,000 series or the 4395A,
4396A/B can search orders of magnitude faster than conventional units.
http://www.prc68.com/I/4395A.shtml

Note that the 4395A uses a 12 MHz wide analog IF feeding a fast DSP based
receiver.  This allows things like a real 1 Hz IF bandwidth and also allows
real power [SQRT(I^2 + Q^2) detection].  All analog SAs use peak detection
since they have no way of detecting power.

Have Fun,

Brooke Clarke
http://www.prc68.com

Brent Gordon wrote:

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