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I need a resistor

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W4HWD, Sep 11, 2019.

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  1. W4HWD

    W4HWD Premium Subscriber QRZ Page

    I need a 1000ohm non-inductive resistor to go across my Inverted-L to ground. Max power used is 500w (if that matters). Where to find one? Or, if you have one lying around I'll send you a couple bucks for it and postage. Let me know.

    Harry W4HWD
     
  2. W4KJG

    W4KJG Subscriber QRZ Page

    More info about the antenna is needed. Is the inverted L end fed or center fed? Do you have any idea what the impedance or voltage will will be where the resistor is connected?
     
  3. KD8DEY

    KD8DEY Ham Member QRZ Page

  4. K0UO

    K0UO Subscriber QRZ Page

    Non inductive resistors in the 250 watt design are very hard to find, and they're going to cost several hundred dollars if you try to find a new one.
    Large used one are becoming almost impossible to find.
    I use a number of them on my rhombic and terminated Vee beams.
    It looks like you're trying to shut to ground so you don't need a resistor I need a shunt coil?????
     
  5. NW2K

    NW2K Ham Member QRZ Page

  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    There’s no reason the resistor has to be non inductive in this application. A suitably large inductance works just fine as a DC and static dissipation device and an inductive large value resistor works fine as well.
     
    AG6QR likes this.
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Harry, can you tell us what the resistor is "for?"

    And will it parallel the feedpoint at the bottom of an inverted L?

    I can't think of any reason to do this; "static drain" (to prevent high voltage from appearing on your feedline due to local lightning transients and other weather conditions) doesn't require anything nearly as low resistance as 1000 Ohms.
     
  8. KB1CKT

    KB1CKT Ham Member QRZ Page

    What is the impedance at the antenna base? If it's around 50 ohms, then I'd probably use some 1W carbon resistors in the 100k region. Maybe use some in series if worried.
     
  9. W4HWD

    W4HWD Premium Subscriber QRZ Page

    It is for static drain. I picked 1000ohms because I Googled it and read some old posts.

    Base Impedance is ~41 ohms.
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Probably a typo, or just a mistake.

    If you place 1000 Ohms across your 41 Ohm load, at 500W output power, you'll be dissipating ~20W in the 1K resistor and of course lose that power when you transmit.

    A static drain resistor can be more like 50K Ohms to do this job. Actually, it can be an RF Choke instead of a resistor, and using the right one, it won't dissipate any power at all but will drain static down to 0V.:)
     
    AG5CK, WA7PRC, WB5YUZ and 3 others like this.

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