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USB spectrum analyzer

Discussion in 'Electronic Design' started by Raveninghorde, Oct 3, 2009.

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  1. I'm looking for a USB spectrum analyzer for occasional use.

    My immediate requirement is to cover the range 100kHz to 3MHz but up
    to 30MHz would be good.

    Any recommendations based on personal experience?
  2. Joerg

    Joerg Guest

    It's an unserved market. You can get one based on a Winradio but IIRC
    it'll set you back north af $1500. Then there's the Icom R1500 for $600
    or sans controller pod as the PCR1500 for around $500. Not much out
    there in terms of (reliable) spectrum analysis software, so to make it
    fancy you'd have to write some.
  3. Hammy

    Hammy Guest

    If you feel ambitious this is a home brew 1GHz one.

    Then again if you have a DSO they come with FFTmay be good enough for
    your purpose.
  4. Nico Coesel

    Nico Coesel Guest

    Most DSO have spectrum analyses capabilities. Just don't expect a wide
    dynamic range.
  5. Joerg

    Joerg Guest

    Problem is, there isn't any market for this so you'd have to roll your
    own. Even 9kHz and up for regular pre-compliance is considered too small
    a market by some. Although I am convinced they are wrong about that
    because nobody has test-marketed any serious <$1k gear there.
  6. Joerg

    Joerg Guest

    Not very. +/-3dB would be good enough for most EMC pre-compliance.
    Dynamic range must be as large as possible though because you may have
    to hunt a wee spur inside an OEM system you don't know.

    Not so much for EMC work. But when designing switchers or when people
    aren't careful with conducted EMI measurements, yes, it can die fast.

    1GHz usually suffices. If you include 2.45GHz that creates a much larger
    market, that of all the "PC doctors" with their refurbed ambulances.
  7. Joerg

    Joerg Guest

    AFAIK it does not, like most VNA's don't :-(

    Usually there's an I/Q detection with pretty much zilch in bandpassing
    before it. So they aren't very useful for that to begin with.
  8. Hello,
    You can try them :
    we have bought one of their RF series (HF6060-V4), usable for qualitative
    measurements at least if you connect it to a PC (the local LCD is, well,
    limited). Not top range performances, but cheap.
  9. Joerg

    Joerg Guest

    Thanks, that's better because there was not hardware link. But 250 Euros
    for max 30MHz? I can't really get very far with that. Might be ok for
    the OP though.

    I wonder why they are still advertising DRM. AFAICT that's pretty much
    dead. As I had been predicting ... :)
  10. Joerg

    Joerg Guest

    A limiter? Well, maybe I should get cracking on the design then. Oh
    wait, I live in Taxafornia, darn ;-)

    Just a diode clipper ain't cutting it for spectrum because you get
    intermodulation galore. Neighbor answers his cell ... ka-crash.
  11. Joerg

    Joerg Guest

    Would be nice if they made one for the typical EMC pre-compliance range
    from 150kHz to 1GHz. Had a chat with the key designer, and it seems they
    either don't see that market or don't want to play there (which would be
    very weird).

    How does yours behave in the presence of large inband signals?
  12. Joerg

    Joerg Guest

    Yeah, I was told it does go lower than the datasheet. However, the V4 is
    priced quite steeply.

    This is pretty cool:

    Anyhow, it all pre-compliance and doesn't replace the trip to the EMC
    lab. The measurement precision is quite a bit different there. The last
    step must be unobstructed free range and properly weighted receiver
    logging. In winter that's not always pleasant but it has to be done.
  13. Hello all, hello Joerg,

    I've done a quick test of our Spectran HF6065V4 with a dual tone input
    signal (two clean CW signals, 926MHz and 925.9MHz, -10dBm and -12dBm
    respectively). I've measured the output both with the Spectran and with an
    Agilent E4406A as a reference with similar setup (1MHz span, 1KHz RBW, full
    VBW, 0 dB ref level, 100dB range, preamplifier off for the spectran).

    Have a look here for the results :

    Well, as I said the Spectran is usable and the measured values are nice, no
    visible mixing products in that test, however the noise floor is, well,
    quite different... The equipment price too ! That doesn't mean that a low
    cost product as the Spectran shouldn't be used, we bought it and we are very
    pleased, but it should be used carefully, and in partical when phase noise
    is important... Do you agree ?

  14. Joerg

    Joerg Guest

    Ouch, that comparison gave the Spectran a black eye. Although it
    probably would have been more fair if the Spectran was connected to a PC
    for display.

    I've heard from people that it really has a hard time when you must
    measure inside a crowded bands with dozens of other strong signals, such
    as the FM band near a large city. Anyhow, I could not live with that
    sort of noise floor.

    Thanks for the comparison, Robert.
  15. Joerg

    Joerg Guest

    Quite expensive. I mostly use a computer-controlled scanner (Icom R1500)
    for spectrum, about $500-$600 depending on whether you want a standalone
    feature or just PC-based. For 5000 Euros I could get a nice full-blooded
    spectrum analyzer off Ebay.

    Accuracy is good but I am more concerned about performance in the
    vicinity of lots of other (legitimate) RF.
  16. Joerg

    Joerg Guest

    It's still a lot of money. AFAIR the antenna they usually ship is a
    shark-fin shaped sort, looks like a shortened log-per might be in there
    but that I dont' know.

    That is very commendable of them. Although except for some of the big
    mfgs that's quite customary these days. When I bought my last DSO I was
    pleasantly surprised about a note in the accompanying docs saying that
    free PC-control software could be downloaded for the scope. No more USB
    stick file ferrying in the lab.

    Thanks, Mark. Kind of hard to see because the resolution doesn't allow
    reading the scale factors. I wonder whether the raised noise floor from
    your DUT (green) on the left side is really there or analyzer-caused. My
    common job is that I have to find a really tiny noise peak inside a
    thicket of other legitimate signals, in order to reduce self-pollution
    in a system. Other jobs are finding potential EMI issues without having
    a screen room available. The toughest was a place right next to a busy
    runway. There, any sort of receiver or analyzer has to be able to
    swallow all this without a raise in noise floor or intermodulation.
  17. Joerg

    Joerg Guest

    Yes, indeed. On most sites that's indicated with a zoom marker but not
    here. Was this taken in a screen room? Reason I ask is that the dynamic
    range is set very low and the usual FM band spectrum chunk isn't there.

    The typos in the menu are kind of funny, like "Bandwith", "Profil"
    (that's definitely German ...) or "Referenc". But it's the same on my
    Taiwan-engineered DSO, just a different accent ;-)

    A bicone? They aren't all that great above 300MHz unless theirs is
    special. You can often buy bicones for a few hundred Dollars at auctions
    but you'd have to make sure the joints aren't too tired or bent. Those
    things tend to fall over a lot.
  18. Joerg

    Joerg Guest

    You could probably whip up your own amp around an MMIC if the Spectran's
    sensitivity isn't good enough. Same for antennas, the only challenge is
    to get them calibrated against a rental with current cal sheets or

    No FM stations? Wow. Do you live somewhere in the boonies in Nevada or
    Arizona? At least there is a signal in the airband so you aren't alone
    out there :)

  19. I managed to borrow an HP 8558B for a few days. It does more than I
    need for this problem.

    It is a shame it is so heavy.
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