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need spectrum analyser

Discussion in 'Electronic Design' started by Jean-Philippe, Dec 31, 2003.

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  1. Hi!

    I wish to build a spectrum analyser (100 kHz to 1GHz - at leas 500
    MHz) and have not found on the net the schematics or sample
    design.

    Is there a site or a place whith such a study ?

    Thanks and best wishes for new year.

    My true adress is : j_p_tremblay(at)hotmail.com
     
  2. Not really.
    It all depends on the finer details.
    A simple machine can be built with a VCO doing the range, a mixer
    a few filters and a logamp. A simple VCO is not able to do 100kHz
    to 1GHz though. It needs someting more sophisticated.

    Questions to be answered first are
    -the sensitivity : is -60dBm sufficient ? If not how much ? -90dBm ?
    -dynamic range : are 60dB sufficient ?
    -noise floor : what is the weakest signal you want to measure ?
    -the bandwidth : is 100kHz filter bandwidth suficcient ? If not what else ?
    -stability of the frequency : and so on ...

    There are quite useable machines at http://www.hameg.com/en/index.htm
    Have a look at the HM5012-2

    Rene
     
  3. Active8

    Active8 Guest

    You need to check the Amateur radio links.

    GBPPR 0 - 1000 MHz Tracking Generator is the closest I can get you
    to a keyword or so. you do use google.com, right?
     
  4. Rick

    Rick Guest

    I looked around for a cheap solution to a SA a few months back, but didn't
    really find anything. For some reason, spectrum analysers tend to hold
    their value much more than other test equipment.

    For example, I can buy a 1Ghz 7104 tektronix mainframe with a few plug-ins
    such as a timebase and amp for about $350-$500 on ebay, yet a 7L12, 7L13, or
    7L14 SA plug-in fetches anywhere from $700 to $1000. The 7104 was much more
    expensive originally than the 7L* plug-ins. Go figure.

    Even HP stuff from the 70s fetches quite a bit of cash. Forget gold as a
    hedge against inflation, buy old spectrum analyzers! :p
     
  5. Hello Jean-Philippe,
    yes, here are some useful links to many other links for self made SAs.

    You should start as usual with Google.

    The magic search phrase has been: AD8307 spectrum analyzer

    Just two links from the first page hit:
    http://www.qsl.net/n9zia/spec/
    http://www.nitehawk.com/rasmit/sa50.html

    There are many other interesting links from this search.

    Best Regards,
    Helmut
     
  6. Jim Yanik

    Jim Yanik Guest

    Better to just buy a used SA or scope mainframe and SA plug-in,like a TEK
    7000 series and a 7L12,7L13,7L14 plug-in,or a stand-alone
    2710,2711,2712,2714,or HP analyzers,regarded as the best used SA's
    available.

    An old TEK 1401A spec analyzer can work with your bench scope and give you
    up to 500Mhz ,but radio hams really love them.
     
  7. mike

    mike Guest

    Make sure you understand your requirements. Your frequency range
    implies that you have some pretty stringent requirement,
    OR
    you haven't a clue and are just throwing out DC to light numbers.

    Think carefully about what you NEED. A SA that has narrow enough
    bandwidth and low enough incidental FM to be effective at 100 KHz and
    still make it to 1GHz. is NOT a DIY project...for most of us.
    Even if you had the schematic, you probably couldn't make it work.
    Ask me about my failed attempt to build a simple YIG tester.
    20MHz/mA. How much FM can you stand?...do the math.

    For overview information, you can get some service monitors with
    built-in spectrum analyzers.
    There have been a lot of designs using TV tuners.
    If you're interested in anything narrow band, many of the DYI designs
    will be useless. The fm noise/drift can be greater than the bandwidth
    you need. You can get some interesting results from 1-30 MHz. with
    a programmable communications receiver. Set frequency, read s-meter,
    repeat as necesary. Slow, uncalibrated, but can be useful.

    mike

    --
    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Honda CB-125S $800 in PDX
    TEK Sampling Sweep Plugin and RM564
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  8. SioL

    SioL Guest

    http://www.vhfcomm.co.uk/matjaz-analyser.htm

    This guy, Matjaz Vidmar, designed a very good spectrum analyzer.
    It can be made at home, but requires a skilled person.

    Have fun!

    SioL
     
  9. mike

    mike Guest

    I was interested in that a while back. If someone posted the actual
    data, it might be useful. A link to buy back issues to find about it
    is...
    mike

    --
    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Honda CB-125S $800 in PDX
    TEK Sampling Sweep Plugin and RM564
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  10. mike a écrit :
    <...>
    You'r right.

    Truely, I am tired to be blind when I build Tx. In fact, only some bands
    are of interest :
    CB (26 to 30 MHz)
    RC (35 to 42 MHz, 70 to 75 MHz)
    Ham (3,5 to 22 MHz, 144 to 146 MHz)
    Data comm (430 to 440MHz, 900 to 1000 MHz)

    resolution should be 1 kHz. A kind of panoramic receiver could be
    sufficient with several band pass (i.e. 3 kHz, 10 kHz, 30 kHz, 100 kHz,
    300kHz an 1Mz). In that way, is it possible to use a scanner as a base
    (noise, sensitivity, stability, etc) ?

    I must say I am a retired electronic engineer and so I have much time (and
    already some equipments : a100Mhz oscilloscope, 40 channel logic analyser
    with 50 MHz sampling, RF generator 500 kHz to 300 MHz, function generator
    1Hz to 11 MHz) and skill in programming (VB, C++, 805x ASM).

    I tried to buy a second hand equipment but it is virtually impossible to
    find something in good condition and less than 10 years old at an
    affordable price (less than 500$). I asked old fellows from Tektronix (I
    was a field engineer some 30 years ago) but their customers (mainly
    administrations) prefer to destroy old equipments rather than to sold them
    to OM's.

    regards.

    Thanks to all for your answers.
     

  11. With some knowledge and connections to useable equpment much is doable.
    Ok, as tracking generator I'd recommend a DDS, such as the Analog Devices
    AD9858 doing 400MHz++, its datasheet has some application samples on how
    to reach 2GHz +-1500GHz.

    Rene
     
  12. mike

    mike Guest

    Take it one step further. What is it about Tx that you're trying to
    determine?
    For transmitters, sensitivity may not be an issue for you.
    Absolute calibration may not be an issue.
    You may be able to get by with 40dB of dynamic range.
    Shielding will be an issue.
    Spurious responses will be an issue if you're looking for spurs.

    Designing a good spectrum analyzer is one of the hardest DIY projects
    I can think of. There's a lot of art that isn't obvious from the
    schematics. Take a look at the front panel of a commercial SA.
    There are a HUGE number of variables to control. And they interact.
    Just the logistics of the human interface is a daunting task.
    I think you have your sights set too high. A 30 year old spectrum
    analyzer is gonna be way better than what you can build yourself.
    It's rumored that the TEK policy has recently been relaxed and you
    can indeed buy old tek stuff once again. Call your buddies in field
    service and have them watch out for you.
    mike


    --
    Return address is VALID.
    Bunch of stuff For Sale and Wanted at the link below.
    Toshiba & Compaq LiIon Batteries, Test Equipment
    Honda CB-125S $800 in PDX
    TEK Sampling Sweep Plugin and RM564
    Tek 2465 $800, ham radio, 30pS pulser
    Tektronix Concept Books, spot welding head...
    http://www.geocities.com/SiliconValley/Monitor/4710/
     
  13. Jim Yanik

    Jim Yanik Guest

    I find it hard to believe that a company would destroy old test gear,rather
    than sell it to a used test equipment company and recover some of their
    investment.Even TEK sold off old test gear by the pallet.They do this
    through Recycling and Material Salvage(RAMS),and have a company store on
    the Beaverton campus when one can pick thru all their scrap stuff.

    I looked on Ebay;
    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2583419214&category=2539
    7
    A HP SA for <$500US.

    Some TEK SAs that are older than 10 years are still good units to have.
    HP has a very good rep for spec analyzers.
    You need to check the used equipment companies,the ones that recondition
    and cal before they sell.A good SA is worth more than $500US,IMO.

    You aren't going to build one nearly as good as a 15 yr old SA.
     
  14. mike a écrit :
    <...>

    I found something interesting (but at lower frequency that I need) at :

    http://www2.arrl.org/tis/info/testproj.html

    There is a set of 2 *.pdf files not reserved to members which describe à50 KHz to 70MHz SA.

    regards
     
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