Component Identification?

Discussion in 'Radio Circuits, Repair & Performance' started by W4FBI, Sep 18, 2019.

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  1. W4FBI

    W4FBI Ham Member QRZ Page

    I thought I was pretty good at reading schematics. C= capacitance R= resistance, etc.

    I am working on a Flex 5000A Antenna Tuner (schematic attached). It lists L12 as 'W950'. L usually means inductor. In this case, I think it means some sort of Ferrite. Several of the regular inductors are listed in uH (as expected).

    There is no Parts List associated with this schematic - so, I'm not sure what a W950 is.

    Seems there are two types on the schematic; W950 and W650

    It's a surface mount - guessing 1206 size

    Any thoughts on this?

    Attached Files:

    Last edited: Sep 18, 2019
  2. K7JEM

    K7JEM Ham Member QRZ Page

    Probably a ferrite bead over a piece of wire.
    IK8TNG and WA7PRC like this.
  3. K7MEM

    K7MEM Ham Member QRZ Page

    Judging from their position in the circuit they are probably surface mount ferrite beads. The numbers are possibly just part numbers.
  4. W4FBI

    W4FBI Ham Member QRZ Page

    Well, I think you guys are correct.

    I measured the DC resistance of the good W950 - about 0.3 ohms. (Ferrite)

    I now believe the '950' nomenclature might represent the impedance of the device. I looked them up at and they all have a DC resistance of less than an ohm, but the impedance varies with the model of the device.
  5. AA3EE

    AA3EE Ham Member QRZ Page

    W usually indicates a wire jumper. Could be a 0 ohm resistor. Or an SMD inductor, especially where they're at in the schematic. Pick something with a high impedance at HF, it's not a tuned circuit so the value isn't critical. It's there to stop noise.
  6. AG6QR

    AG6QR Premium Subscriber QRZ Page

    That is probably impedance at 100MHz. That's a common way of rating small ferrite beads. The impedance at a different frequency will vary widely, and it's not just a simple formula like it would be for an air core inductor. See the data sheets.

    For example:

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