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Author Topic: Static Discharge and Build Up of..Something...I don't Know  (Read 4897 times)
KB9TYT
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Posts: 5




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« on: July 22, 2012, 12:09:18 AM »

At my QTH in Rockford, Illinois we have had the worst heat wave in a BILLION years.  A little exaggeration.
With the heat wave I have experienced something I never had before.

First, my antenna and radio equipment and radio room is grounded to the HILT but I've been hearing static discharge on my radio that practically knocks it out.  It sounds that way any who.  I'll be listening to a QSO and it sounds like a direct electrical hit like someone is outside touching my antenna with 1000 volts.  Maybe it's a UFO.  HI HI
What is that if I am grounded so well.  Need more grounding???  If I ground anymore than what I have, GOD himself will be sucked into the ground if he strikes.

Second,  I notice lately something I think is loading up on my equipment.  Even though my SWR is 1.2 to 1, some times my Yaesu will kick out and I need to turn the power down to about 70 watts to run without a kick out.  Sometimes not.  I just cannot figure this one out.  Sometimes I by-pass my autotuner and turn off the tuner on the Yaesu and run at 2.5 SWR and sometimes almost 3 and I can run 100 watts.  As soon as I even just use the Yaesu tuner I need to turn down the power to 70 or 80 Watts otherwise it kicks off.  If I don;t use the radio tuner and just use the LDG tuner to bump down the SWR, well, my radio kicks off unless I lower the power.  This all has been happening since the big heat wave.  Maybe just a coincidence. 

Any Elmer's out there that can educate me??

Tim
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TANAKASAN
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Posts: 933




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« Reply #1 on: July 22, 2012, 12:18:35 AM »

A couple of things you can try.

Firstly on RECEIVE ONLY stick a neon bulb across the antenna connection and look for flashes, this will be static on the antenna connection. On transmit this may flash over so do not connect a neon bulb on transmit.

Secondly, put a multimeter (or even better a scope) across your 110V mains supply, that could be where the crud is getting in.

Tanakasan
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KA4POL
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Posts: 2097




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« Reply #2 on: July 22, 2012, 01:52:57 AM »

The dryer the air the lower the conductivity, i.e. the higher the build up of charge. You want to receive something so it is not possible to avoid also receiving the unwanted charging. You hopefully have some overvoltage protection in front of your receiver.
It does not become clear what setup you are using concerning the antenna tuners. You are not using two in a row at one time? You should not be doing that. Where do you measure SWR? It could be misleading if not in the right spot.
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K4SAV
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Posts: 1850




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« Reply #3 on: July 22, 2012, 08:19:20 AM »

You have all the symptoms of a bad connection somewhere in your antenna or in the feedline.  It may be difficult to find since it is intermittent.  A bad solder job in a connector is very common, and the connection of the coax to the antenna is a likely spot.

Jerry, K4SAV
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WB6BYU
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Posts: 13486




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« Reply #4 on: July 22, 2012, 09:18:25 AM »

What type of antenna are you using?  How is it grounded?

I'm going to make a guess that if you put a coax T connector in the coax between your
antenna and tuner and connected a 100K resistor across the open side the problem
would go away.

Here's why:

 Let's say you are using a half wave dipole fed with coax, and the coax shield is well
grounded somewhere.  That doesn't provide a DC ground for static build-up on the side
of the antenna that is connected to the center conductor.

A common T-network tuner has a capacitor in series with the coax center conductor
and a coil from the other side of the capacitor to ground.  The coil doesn't provide
a DC path for the antenna, either, because the capacitor is blocking it.  So the full
build-up of static charge appears across the output capacitor.

When the voltage build-up on the antenna gets high enough, it can exceed the voltage
rating of the capacitor, causing it to arc.  I've had the capacitor in my tuner arc over
every few seconds in particularly bad conditions.  This usually doesn't hurt an air
variable capacitor, but fixed capacitors in a relay-switched tuner might not get off
so easy.

But if your equipment includes a coil across the coax - perhaps part of a filter, or the
input winding on a transformer, that provides a DC ground when the rig is connected
directly to the antenna, though not when there is a tuner in series.

Adding a large shunt resistor (or a suitable RF choke) in the coax between the antenna
and the tuner provides a static drain to ground even with the tuner in line.
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K4SAV
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Posts: 1850




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« Reply #5 on: July 22, 2012, 10:30:12 AM »

You have all the symptoms of a bad connection somewhere in your antenna or in the feedline.  It may be difficult to find since it is intermittent.  A bad solder job in a connector is very common, and the connection of the coax to the antenna is a likely spot.

Jerry, K4SAV

Add to my list of bad connection possibilities, a bad connection in the tuner.  

I have never seen a transmitter fold back power because of static build up on an antenna.
« Last Edit: July 22, 2012, 10:36:08 AM by K4SAV » Logged
N4NYY
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Posts: 4818




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« Reply #6 on: July 22, 2012, 11:42:48 AM »

Are you hearing static on the radio? Or are you talking about ESD? ESD will knock out your radio permantently, if you have a lot of SMD components. One way to reduce ESD, is to get the humidity level to about 50% or so.

If that is not you problem, and you are hearing snap, crackle, and pops on your radio, I would agree with the others, and you have a problem in the feed or antenna. 
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AA4PB
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« Reply #7 on: July 22, 2012, 12:17:34 PM »

I've had cases where dry air blowing over a wire dipole antenna caused a static charge to build up until it reaches a high enough voltage to arc across something. Suddenly the S-meter pegs and I hear a high frequency "whine" that gradually decreases in strength and then suddenly stops. The solution is to put a 100K resistor across the antenna to ground connection in order to discharge the static and prevent it from building up to a high enough voltage to arc.

The 100K value is large enough that it won't disipate much power (even a 1/2W resistor is okay) in a 50 Ohm antenna system - but it draws enough current to keep the static charge from building up.

If you are still using that vertical, just put the resistor between the base of the antenna and the ground connection.
« Last Edit: July 22, 2012, 12:21:13 PM by AA4PB » Logged
N0SYA
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Posts: 369




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« Reply #8 on: July 22, 2012, 01:02:14 PM »

I've had cases where dry air blowing over a wire dipole antenna caused a static charge to build up until it reaches a high enough voltage to arc across something. Suddenly the S-meter pegs and I hear a high frequency "whine" that gradually decreases in strength and then suddenly stops. The solution is to put a 100K resistor across the antenna to ground connection in order to discharge the static and prevent it from building up to a high enough voltage to arc.

The 100K value is large enough that it won't disipate much power (even a 1/2W resistor is okay) in a 50 Ohm antenna system - but it draws enough current to keep the static charge from building up.

If you are still using that vertical, just put the resistor between the base of the antenna and the ground connection.


Great advice. Add a gas discharge tube of some type and be done with it.
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If you have a clumsy child, you make them wear a helmet. If you have death prone children, you keep a few clones of them in your lab.
W0BTU
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Posts: 1803


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« Reply #9 on: July 22, 2012, 06:26:20 PM »

Great advice. Add a gas discharge tube of some type and be done with it.

Yup!

Neon lamps cannot take nearly the impulse surge current that a good gas discharge tube (GDT) will. I've seen NE-2s (etc) explode and scatter glass all over the place without much voltage at all applied to them. It's hard to bead a good ceramic GDT and a proper resistor in parallel.

The resistor will not only keep the voltage lower than if we used a GDT by itself, but it will greatly prolong the life of the GDT.

Here's general data on the GDTs I use in my Beverage antenna boxes: http://www.bourns.com/data/global/pdfs/2027.pdf
« Last Edit: July 22, 2012, 06:31:57 PM by W0BTU » Logged

KA4POL
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Posts: 2097




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« Reply #10 on: July 22, 2012, 09:39:38 PM »

I'd still like to see his setup and use of antenna tuners.
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K6AER
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Posts: 3530




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« Reply #11 on: July 22, 2012, 09:54:14 PM »

Put a 2 watt 2 Meg resistor from the antenna center lead to ground. On a balanced line use two resistors to ground. That is what we do in Colorado where the humidity is about 20%.
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KA4POL
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« Reply #12 on: July 22, 2012, 10:12:56 PM »

Hopefully non inductive ones  Grin
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K4SAV
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Posts: 1850




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« Reply #13 on: July 23, 2012, 06:11:23 AM »

Did you guys even read the original question?  How are these added resistors or "gas discharge tubes" going to keep his transmitter from "turning off" when the tuner is used?
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KA4POL
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Posts: 2097




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« Reply #14 on: July 23, 2012, 06:21:51 AM »

Did you read my question about the tuners? It is still without answer. We need to see what he is doing.
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