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Bleeding off static from a vertical

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K3RW, Jan 6, 2018.

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  1. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    The static wics I sell and install are very high resistive elements of 20K to 50K ohms, and some antennas have them incorporated on the trailing edge at the tip.

    Without a wic, you can see and hear the static drain off various parts of an airplane, and it is worse when you listen with an AM radio. With the wics, you can still see the static discharge, but without any noise in the radios. The plasma glow is different as well.

    The wics are installed at the extreme ends of the wings, elevators and rudder, because the static charge builds on the skin of the aircraft, and as it is all 'like charges' the static repells itself to the extreme tips of the aircraft structure, including the antennas.

    After I install the wics, I can test them to verify the wics are working by using a VERY high voltage power supply. Normally, I use 30,000 volts with 100 to 150 microamps of current. I have accidently touched the wand to my leg, and it delivers a painful shock, more than scuffing your feet on carpet in the winter time...
     
  2. W5DXP

    W5DXP Ham Member QRZ Page

    You're right, but the DC path does eliminate the arcing caused by static buildup which was my biggest problem in Arizona.
     
    N0TZU likes this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    AM radios are what are used in aircraft...

    In an aircraft without static-wicks installed, the Corona forms right at the tip of the Comm antennas. They are dc-grounded to the airframe, and they have the sharpest "point", so that is where the air ionizes to create the Coronal Plasma, and almost all of the charge that the aircraft accumulates as it flies through clouds of charged particles (rain droplets or snow) is dissipated right there. Corona is less on wingtips and rudder tip because they have a huge radius of curvature compared to the tips of the antennas.

    The reason why static-wicks are installed near the wing-tips and rudder-tip on aircraft is because those places get the plasma as far away from the comm antenna as possible... I have installed lot of them....
     
    Last edited: Jan 10, 2018
  4. W9GB

    W9GB Ham Member QRZ Page

    Of Course ... since an AM Broadcast Transmitter is “one-way communication” (broadcasting) to the general public. Amateur Radio, as stated in Part 97, is two-way communications.
    The “real world” example was to demonstrate that atmospherics produce a substantial “charge” on vertical radiators — that will dissipate to its best path to ground.
     
  5. K0OKS

    K0OKS Ham Member QRZ Page

    Jack in the Box antenna balls: reducing coronal discharge for twenty years.
     
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    ok... Conductive sphere. Maybe you could wrap those in aluminum foil...
     
    NH7RO likes this.
  7. AI0K

    AI0K Ham Member QRZ Page

    Which has absolutely nothing to do with the fact that your spark gap doesn't help with static noise on reception except possibly make it worse.
     
  8. KD8WU

    KD8WU Ham Member QRZ Page

    In the spring I'm planning on installing (probably) a 4BTV on a 10' tripod on top of my garage (tripod already there from my 10/15m antenna), so I looks like I should have SOMETHING to bleed off the static and may go this route. So, am I correct in "assuming" that it doesn't matter which end of the coax this goes?


    Thanks,
    Bob - KD8WU
     
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    Imagine that you have an Ohmmeter with 100ft test probes. Put one probe on the active antenna element (usually where the center-conductor of the feedline connects). Put the other on the ground rod at the base of the antenna structure (i.e. connected to earth). If the Ohmmeter reads infinite resistance (open), then add a bleeder (anywhere you like) such that the Ohmmeter shows some continuity to earth.

    If you are relying on your transceiver having an internal DC resistance across its SO239, then the path would be from the active antenna element, down the coax center conductor, through the radio, back out the coax shield, to whatever lightning grounding system the coax passes through.

    The transceiver likely has multiple ground paths from its chassis to other things that likely connect to the earth ground rod that is part of your electrical distribution panel.

    If you have an earth-grounded entrance panel on an outside wall of your ham shack where all of your antenna coaxes come through (maybe with gas gaps), then shunt each coax with a megOhm resistor at that point...
     
    Last edited: Jan 12, 2018
  10. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    No it doesn't matter in general but it might depending on your setup.

    Mine is right at the vertical for two reasons. First, because the auto tuner and relay/loading coil box is at the base of the vertical and I want to bleed the static beforehand. Second, because I don't want to get a little static shock if I'm working on the antenna in dry windy conditions.
     

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