Ken -

RF can be a real nightmare to work on.  I have seen/designed PCBs that were
"tune-able" by adding a blob of solder in the "right" place, or by angling a
component across the pads instead of mounting it square. I once saw a tech
turn a non-polarized cap end-for-end to get the circuit to work in spec. The
real problem is not the tolerance of the board or the tolerance of the
component but the net tolerance of the system (if you have a few spare
months(?) maybe you could work this out). What I am saying is that a tighter
tolerance may reduce the number of components that function marginally but
it probably will not eliminate the problem all together. And just think this
will only get worse as frequencies go up and size goes down.

An eternal optimist,
Jeffrey A. McGlaughlin
PCB Designer
Battelle Memorial Institute
Columbus Ohio
[log in to unmask]


        -----Original Message-----
        From:   Ken Patel [SMTP:[log in to unmask]]
        Sent:   Thursday, 26 August, 1999 17:51
        To:     [log in to unmask]
        Subject:        [TN] Any connection: Impedance Control value & RF
Board

        Experts,
        We have couple of RF boards which are relatively new to us. Many
times, we
        have to replace passive components to make it work. Hence, I have
this
        hypothetical question for you. Is it due to not having correct
impedance
        value even though measured value on coupon falls within 50+/-10
ohms%? Do
        you think we may to have tighten our current impedance specification
        (50+/-10 ohms%) if there is a relationship?

        Being a mechanical kind of guy this question may sound stupid! Hope
to hear
        from many of you.

        re,
        ken patel
        ______________________________________________________
        Ken Patel                       Phone:  (408) 490-6804
        1708 McCarthy Blvd.             Fax:    (408) 490-6859
        Milpitas, CA 95035              Beeper: (888) 769-1808

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