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RF signal generators

Discussion in 'Electronic Design' started by George Herold, Dec 12, 2012.

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  1. My boss is looking to spend some of this years profit. He’s been
    lusting after an RF signal generator. (We could use something that
    would go above 50MHz.)
    I know very little about them, and so I am looking for any
    recommendations, or brands to stay away from.

    Any thoughts on an Agilent EE4436B? (250 kHz to 3GHz.)

    Thanks

    George H.
     
  2. E4436B ? Obsolete.. you might get a good deal. The replacement is
    $45K, glad to hear that there's enough profit for it to be a problem.
    ;-)
     
  3. Grin, Well there is some profit sharing at the end of the year. Just
    don't tell the other employee's that we buy new tech 'toys' before
    figuring what the profit is/ was.

    Say if I have a GHz spectrum analyzer with a tracking generator can I
    just use the tracking generator as a swept RF source? That might be
    better than a signal generator for lots of things. (Can you park the
    tracking generator at one frequncy?)

    George H.
     
  4. Yeah some for a few $k on ebay.

    George H.
     
  5. TTman

    TTman Guest

    My boss is looking to spend some of this years profit. He’s been
    lusting after an RF signal generator. (We could use something that
    would go above 50MHz.)
    I know very little about them, and so I am looking for any
    recommendations, or brands to stay away from.

    Any thoughts on an Agilent EE4436B? (250 kHz to 3GHz.)

    Thanks

    George H.

    What would be the use of 50MHz ? 500MHz maybe....What RF stuff runs at<50MHz
    ?
     
  6. Nico Coesel

    Nico Coesel Guest

    AFAIK yes and yes. The only downside is that you probably can't
    modulate the signal. Rigol has a bunch of new spectrum analysers for
    very reasonable prices so you can buy new for half the price of second
    hand.
     
  7. Guest

    LOADS of RF stuff runs at <50Mhz!

    I got a sweet deal on a used 10hz to 5.4Ghz Tek sig gen the other day. Paidonly $195 for it! It does have a problem with the PSU section, though, theseller said. Needs a fancy new electrolytic that Tek wants about $250 for.Not sure why it's so expensive, but since I'm only a hobbyist I could probably get away with a regular electrolytic cap for a fraction of the price, I reckon. If anyone knows better and I'm likely to screw the thing up, please disabuse me of my ignorance!
     
  8. Well sure I've got a DDS func. gen. that does DC to ~50MHz.

    If audio stops at 100k - 1MHz,

    Then there's plenty of stuff to do.

    pulsed nmr in permanent magnets ~20MHz.

    diode laser modulation, there's phyiscis from 1MHz to 6.8GHz.

    (Hmm, other stuff too... but most of it's on the same theme,
    an electron (atomic) spin resonance at lowish fields,
    or a nuclear spin at ~1T fields.)

    George H.


    There's this coax-impedance matching, 1/4 wavlength
     
  9. (Unless I hack it... I was just watching David Jones do a tear down of
    the
    Rigol on his eevblog.)

    Rigol has a bunch of new spectrum analysers for
    I downloaded their manual, but haven't read through it yet...

    So if I park the TG, I get something like a noisy VCO output at the
    right frequency? That could work.

    I must admit a spectrum analyzer, would be more useful than a signal
    generator.

    (maybe we should get both!)

    George H.
     
  10. Hmm, see if you can find out what the 'fancy' part of the spec is,
    more or less ESR would be my niave guess. Then, given the specs,
    someone here may be able to recommend a cheaper one.. with maybe some
    testing on your end to find a good cap in the lot. (You use the
    others for other projects.)
    I've been picking the low esr 'cheeries' out of our 10uF tant, bin to
    use in this LT voltage regulator. (I sometimes think I should just
    trash it. It's fussy and noisy.)

    George H.
     
  11. Phil Allison

    Phil Allison Guest

    "George Herold"

    My boss is looking to spend some of this years profit. He’s been
    lusting after an RF signal generator. (We could use something that
    would go above 50MHz.)
    I know very little about them, and so I am looking for any
    recommendations, or brands to stay away from.


    ** The Wavetek 3000 is one to avoid.

    Unless you just want something to prop the door open with....




    ...... Phil
     
  12. miso

    miso Guest

    Since the spectrum analyzer has a tracking filter, the built in signal
    generator may not be as pure as a stand alone signal generator. However,
    this should all show up in the specs. The same goes for step size. I
    have seen some spectrum analyzers with modulation sources. I think it
    was a Marconi.

    You do know that a network analyzer is way sexier than a spectrum
    analyzer. You can do stuff like model chip components, or better yet,
    evaluate chip components to see which are better. You would need to
    insure the network analyzer has an impedance bridge and a suitable
    fixture for chip components.

    As a bonus, you can sweep your homemade antennas on the network
    analyzer. Just don't tell the FCC since this is basically QRM unless you
    have a anechoic test facility.
     
  13. o pere o

    o pere o Guest

    It depends a lot on what you want to do with it. If you want plain basic
    functionality (CW, AM, FM) an old Agilent 8648C would fit.

    The 4436B, although obsolete as others have pointed out, is a great
    instrument (I have an 4431B here, sadly only up to 2 GHz missing the 2.4
    GHz band). Depending on what you want, you may like some of the options.
    We have the internal baseband generator for IQ generation which might be
    interesting depending on the application.

    Then, you have the 8267 models, which are big $$... BTW, we have to ship
    our unit back to troubleshoot, thank god we had a warranty extension!

    We also have an older Rohde&Schwarz SMIQ04. A good instrument with a
    particular user interface.

    Regarding failures: We have had a significant number of failures with
    Agilent equipment. Had to have the 4436 and now the 8267 repaired. Same
    with a 20 GHz VNA (PNA-L). We had two of the nice 33250A 80 MHz function
    generators failing. A power supply was sent back twice until it started
    working properly for the first time... IMO this should not happen with a
    vendor of good reputation. Regarding Rohde's, we had to send in the
    generator because of an LCD issue.

    Pere
     
  14. o pere o

    o pere o Guest

    You may consider one of the handheld network analyzers that are
    available. They are not top notch in terms of performance but they are
    quite versatile.

    Pere
     
  15. JW

    JW Guest

    Here's a nice bit of info for anyone with those LCD problems (lines, etc)
    The Rohde CMD80 uses the same display and can be had for peanuts on Ebay.

    I have an SMIQ02 that had a bad display with tons of lines in it. Took a
    chance and bought a CMD80 off Ebay and it dropped right in and worked
    perfectly.

    It's currently for sale if the OP is interested. Been sitting on it for
    awhile and would sell it for $850 + shipping CONUS only.
     
  16. Oh there was a fancy HP/ Agilient network analyzer at the Vanderbilt
    FEL when I was there. But it was under someone elses supervision and
    I wasn't allowed to play with it. I think it cost north of ~$50k
    circa late 90's.

    George H.
     
  17. Thanks Pere. Glad to hear that you like the 4431B. There are several
    on ebay for not too much money. Part of the problem is that we have
    only nebulous plans of what to do with it. A swept RF source would be
    useful for some experiments.

    George H.
     
  18. OK thanks JW, I'll give it a look see.

    George H.
     
  19. So do you have a favorite spectrum analyzer with TG? (Say 1 to 2
    GHz.)

    George H.
     
  20. I was watching David J. play with the Rigol TG on his eevblog... The
    TG had an ugly amplitude vs. freq shape, ~ +/-1.5 dB (a +/-3dB spec.)
    I guess that's somewhat expected given the cost/source.
    OK thanks, (Of course whatever band is free-running will be the one
    I'm someday most intereseted in.)

    George H.
     
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