Loading ...
Sorry, an error occurred while loading the content.

Re: 112.36 MHz crystals shipped January 28

Expand Messages
  • Ray Anderson
    When considering the series resonant frequency of decoupling capacitors bear in mind that the SRF shown in the data sheet is a function of the capacitors
    Message 1 of 3 , Jan 29, 2008
    • 0 Attachment
      Softrock-40 Interest Group

       

      When considering the series resonant frequency of decoupling capacitors bear in mind that the SRF shown in the data sheet is a function of the capacitors nominal capacitance and the intrinsic parasitic inductance. In actual use you’ll find the SRF to be lower since the resonant frequency will depend on the mounted loop inductance which is greater than just the capacitor’s parasitic inductance. The mounted inductance is comprised of the following partial inductances: the capacitors inductance, the mounting pad escape inductance, via inductance and plane spreading inductance. So even though a capacitor may show 100MHz SRF on the data sheet, the actual resonant frequency can be considerably lower.

       

      -Ray  WB6TPU

       

       

       

      Re: 112.36 MHz crystals shipped January 28

      Posted by: "Bill Dumke" billd@...   billspiro1

      Mon Jan 28, 2008 6:38 pm (PST)

      Tony,

      Thanks for the crystals.

      Once I designed a very low pulse-stretching video amp that achieved a -3
      dB passband from 5 kHz to 430 MHz. It used 6 transistors, but the
      bypass capacitors AND coupling capacitors were ALL 1.0 uF SMT chip
      caps. And it worked great. Very flat frequency response as well.

      So I kind of doubt the 0.01 uF caps will change much of anything. But
      it would be interesting to see if more output voltage can be obtained
      from the daughter board. I would think that would be the best test.

      I have used series resonant capacitors in microwave power amplifiers as
      well. So they certainly had some good utility, when I needed to run
      high RF currents, and the chip caps were larger than the normal ones
      available in those days, with much more inductance.

      Bill wa9pwr

      kb9yig wrote:

      > Good Morning All,
      >
      > The 112.36 MHz overtone crystal for the 10m RXTXv6.2 beta kit are
      > packed to be mailed today, January 28.
      >
      > Included with each crystal is a strip of twenty-two 0.01uF 1206 size
      > SMT caps for use on the 10m daughter board and some locations on the
      > RXTX board.
      >
      > The 0.1uF SMT caps supplied with the 10m kit pair have a 20 MHz
      > series resonant frequency but still have worked satisfactorily with
      > 10m kits built so far. The 0.01uF SMT caps have a series resonant
      > frequency around 100 MHz so in the interest of doing what is better
      > practice the 0.01uF caps are sent out.
      >
      > Recommended locations for use of the 0.01uF caps include the
      > following:
      >
      > All SMT caps on the daughter board
      > On the RXTXv6.2 board: C53, C54, C55, C56, C57, C58, C59, C60, C61,
      > C66, C67, C69, C70 and C73.
      >
      > Please post your experience with the 10m RXTXv6.2 beta kit.
      >
      > Thanks and 73,
      > Tony KB9YIG

    Your message has been successfully submitted and would be delivered to recipients shortly.