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Scope probe UHF test points

Discussion in 'Radio and Communications' started by Mosaic, Oct 6, 2016.

  1. Mosaic

    Mosaic Well-Known Member

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    Hi all
    This may pertain to the > 300Mhz range but I am looking into mass manufacturing replacements for these:
    http://www.alliedelec.com/tektronix-131-4353-00/70137194/

    Both SMT and thru hole options.

    With a goal of perhaps 0.25 to 0.50 each, brass (quantities of 25) . Suitable for a range of O'scope probe diameters to eliminate most lead inductance issues when experimenting and tracing signal paths or even permanent test points in finished products.

    Any input/feedback is appreciated.
     
  2. Mikebits

    Mikebits Well-Known Member

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    Generally, in RF signal chains, adding test points is a bad idea as it would cause an impedance mistmatch, thus degrading the circuit performance. Additionally, adding any sort of stub in a circuit path will resonate as some frequency causing EMI issues, frequency peaking at some point along the frequency domain among other problems. In short it is just a bad idea.
    Further, adding the scope probe into the signal path will cause loading issues. Typically if you want to break into a signal chain, you would cobble some sort of pigtail into the chain just for test, then return the circuit back to its normal configuration when done.

    One method of sampling off a port would be to use something like a RF coupler (also would add loss in chain), thus maintaining an impedance match. Even in this case SMA connector or similar would be the interface of choice.

    I am not sure how you would be using these connectors, but at the frequencies you have mentioned, I would say your wasting your time to mass produce as most designers would not use them for UHF applications.
     
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  3. tronitech

    tronitech Member

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    I feel sure if you search the Chinese have probably already beat you?
     
  4. dave

    Dave New Member

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  5. Mosaic

    Mosaic Well-Known Member

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    @ tronitech :Well, I've been looking awhile.

    @ Mikebits. What you're saying is not entirely true. There are fixed test points of the type I am discussing in the signal chain in my Agilent E4432B digital 3GHZ signal gen.
    If test points are designed to remain in the signal chain, the stubs are compensated for in the circuit design...an easy matter for the AWRDE suite for RF dev. No frequency peaking would occur. RF couplers and 50 ohm SMA connectors as a replacement for for a testpoint introduce higher cost, physical bulk & loading much greater than my TDS694C. active FET probe, and a test point.
     
    Last edited: Oct 12, 2016

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