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Author Topic: Station grounding.....RF grounding.....???  (Read 10065 times)
KB8BAB
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Posts: 100




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« on: July 11, 2012, 06:41:47 AM »

I got my station finished (for now) and believe I got it right but......the more I read the more I become confused on station/RF grounding. It seems everyone has their opinion.

from what I've read/learned there are several grounding types:
- Equipment grounding
- RF grounding.

My tower is grounded (ground rods at the base) and bonded to the main ground rod for the house.
A copper bus-bar is mounted on the house (exterior) containing the lightning arrestors. This copper bus-bar is bonded to the tower ground.

From there my feed-line into the house is aprox. ~30ft. The entry is through the wall near the tower, but then have to run the feed-line around the room to get to my station.
The equipment is electrically grounded through a surge suppressor plugged into the house 120VAC outlet.

I did nor run a separate ground wire from the (external) bus-bar to the equipment (station)......as it is already electrically grounded through the house...

At this point I don't believe I have RF in the Shack:
- No TVI when transmitting (on any of my tv's)....
- No "radio"voice" coming through any stereo equipment.....
- My PC does not go nuts (right next to the transmitter).....
- I don't get "zapped" by the mic...

But how can I be sure? Is there a way to test / monitor it (without getting "zapped")....

- Is the ground connection from the bus-bar to the equipment essential for RF grounding purposes? Mine would be ~ 30ft...

73's

Bart

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WX7G
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Posts: 5918




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« Reply #1 on: July 11, 2012, 09:16:13 AM »

You have no RF issues that would indicate an RF ground issue. No problem requires no solution.
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K8AC
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Posts: 1465




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« Reply #2 on: July 11, 2012, 04:22:23 PM »

You didn't mention lightning ground at all, but I suggest that, if you haven't already done so, you tie your equipment chassis/cabinets (including PCs) to a common ground point at the operating desk.  I wouldn't depend on the fact that everything is grounded to the electrical service through the plug pin.  The important thing here is to minimize or eliminate the difference in potential between units when a strike hits nearby.  This isn't the only lightning ground consideration of course, but one that, if overlooked, can have unpleasant consequences.

73, Floyd - K8AC
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K9KJM
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Posts: 2416




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« Reply #3 on: July 11, 2012, 09:25:34 PM »

I agree with K8AC.     The most important part of lightning protection is BONDING all grounds together.

Also, A "whole house" surge arrestor installed in the main power breaker box is important.

For some tips on how to do it on a budget:


http://www.scribd.com/doc/14868226/lightning-protectiontaming-thors-thunderon-a-budget


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KB8BAB
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Posts: 100




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« Reply #4 on: July 12, 2012, 04:38:25 AM »

Thanks for the info....

I've got everything bonded together....and am going to look into the whole house surge protection....good idea...
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K1CJS
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« Reply #5 on: July 12, 2012, 10:21:48 AM »

Your ground cable should be as short as possible, and if you have to run the cables around your room to get from the cable entry to the operating desk, then you may have some issues with that ground cable acting as part of your antenna system.  That ground cable should never be more than 5 or 6 feet long.  Then again, you may have no problem.  The only way to see is to put it in and use it.
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W2WDX
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« Reply #6 on: July 13, 2012, 03:57:42 PM »

BTW grounding schemes of any kind (or size) will NOT protect you from a direct lightning hit. If you are hit directly the coax or feedline will most likely vaporize and the remaining charged particles will form the path for the rest of the lightning pulse, along with your tower (which should not vaporize :-). This is because the breakdown voltages of these cables is miniscule compared to voltages of a lightning pulse. The gear will also be seriously affected since it offers a path to ground for the pulse. Don't be misled; the only safety against lightning going into your house is physically disconnecting any wires or cables leading into your home.

Lightning arrestors are only good for relieving energy in near hit or for EMP protection from lightning or very high static discharges. If the arrestor is a gas discharge type only, then repeated pulses of near hits will exhaust the gas over time and then afford no protection of this limited type. A better arrestor has a shunting coil and resistor to ground to discharge voltages directly, without the need for the gas discharge tube firing extending its usefulness. Also a high voltage DC blocking cap is a good addition for this, unless you are using an antenna switch that uses DC on the coax. A series cap like this would block that unless it is injected on the antenna side of the capacitor. And the lack of RF in your shack is probably more a function of you having a well tuned antenna and feedline system then from a lack of grounding.

The station grounding which if made to be able to pass RF energy easily (by keeping its impedance low ... or is it high? Opps brain fart) will not only help keep everything at the same potential, but as a result of this, may decrease ambient background noise in your receiver and potentially help reduce hums in the receiver and audio on transmit ... sometimes. It's not a precise predictable science.
« Last Edit: July 13, 2012, 04:09:32 PM by W2WDX » Logged

KB8BAB
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Posts: 100




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« Reply #7 on: July 13, 2012, 06:27:15 PM »

Thanks for the info....

I realize what I have done will not protect against a direct strike....and as you mentioned I disconnect the cables during bad weather.

RE: My station grounding..
Since the run from the cable entry to the desk is long (~30ft), a direct grounding wire may act as a radiator....not something I'd want...

Searching the web, I found this solution....looks interesting...should work...(See Alternative 2 -The RF Suppressor Ground System in the following link)

http://kc.flexradio.com/KnowledgebaseArticle50426.aspx

Bart

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K9KJM
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Posts: 2416




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« Reply #8 on: July 13, 2012, 11:25:14 PM »

BTW grounding schemes of any kind (or size) will NOT protect you from a direct lightning hit. If you are hit directly the coax or feedline will most likely vaporize and the remaining charged particles will form the path for the rest of the lightning pulse, along with your tower (which should not vaporize :-). This is because the breakdown voltages of these cables is miniscule compared to voltages of a lightning pulse. The gear will also be seriously affected since it offers a path to ground for the pulse. Don't be misled; the only safety against lightning going into your house is physically disconnecting any wires or cables leading into your home.

Lightning arrestors are only good for relieving energy in near hit or for EMP protection from lightning or very high static discharges. If the arrestor is a gas discharge type only, then repeated pulses of near hits will exhaust the gas over time and then afford no protection of this limited type. A better arrestor has a shunting coil and resistor to ground to discharge voltages directly, without the need for the gas discharge tube firing extending its usefulness. Also a high voltage DC blocking cap is a good addition for this, unless you are using an antenna switch that uses DC on the coax. A series cap like this would block that unless it is injected on the antenna side of the capacitor. And the lack of RF in your shack is probably more a function of you having a well tuned antenna and feedline system then from a lack of grounding.

The station grounding which if made to be able to pass RF energy easily (by keeping its impedance low ... or is it high? Opps brain fart) will not only help keep everything at the same potential, but as a result of this, may decrease ambient background noise in your receiver and potentially help reduce hums in the receiver and audio on transmit ... sometimes. It's not a precise predictable science.

That is flat out B.S.!!!!!!!!!!

THINK it over!   Commercial repeater tower sites, Cellphone towers, Broadcast stations, Police, Fire, Ambulance, Etc. and MANY hams with TALL towers take direct lightning strikes MOST EVERY storm, With NO damage to equipment!

To say that "nothing will protect" from a direct strike is flat out old wives tales ignorance!

While it does take some time and effort to install a good protection system, LOTS of folks do.
(Good BONDING of ground systems is the most important vital part to get right. The "arrestor" is really pretty low on the importance scale)

Anyone telling you to "disconnect" coax without putting them to a good ground is giving very poor, DANGEROUS advice!

Leaving a disconnected antenna coax just laying about is about like leaving a stick of dynamite on your table, Unless you GROUND it properly!

Check out W9JI's site, Along with K9STH's for good plans on some tips to build low cost grounds, And:
http://www.scribd.com/doc/14868226/lightning-protectiontaming-thors-thunderon-a-budget

(Give that site plenty of time to load)
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K1CJS
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« Reply #9 on: July 14, 2012, 08:17:09 AM »

BTW grounding schemes of any kind (or size) will NOT protect you from a direct lightning hit....

That is flat out B.S.!!!!!!!!!!

THINK it over!   Commercial repeater tower sites, Cellphone towers, Broadcast stations, Police, Fire, Ambulance, Etc. and MANY hams with TALL towers take direct lightning strikes MOST EVERY storm, With NO damage to equipment!

To say that "nothing will protect" from a direct strike is flat out old wives tales ignorance!  <snip>

Check out W9JI's site, Along with K9STH's for good plans on some tips to build low cost grounds, And:
http://www.scribd.com/doc/14868226/lightning-protectiontaming-thors-thunderon-a-budget

(Give that site plenty of time to load)


It is true that there are grounding schemes that will protect from even a direct strike, but there is still a very good possibility of some sort of damage unless good, top of the line equipment is used in the installation.  Unfortunately, all too many hams scrimp and cut corners, getting cable and equipment that will do the job without planning and getting the good equipment to do it right.  Then they come and say there is nothing that will protect against a direct hit.

THAT is where the fallacy comes in, and that is why these wives tales are told.  Spend the money to do it right, and you won't have to worry about doing it again.  That is what some hams AND all of the commercial sites do, they overprotect sometimes, but they do it right.  Think about it--Why do you think that commercial and public service radio installations (such as police and fire department installations) cost so much?  73!
« Last Edit: July 14, 2012, 08:20:17 AM by K1CJS » Logged
WX7G
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Posts: 5918




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« Reply #10 on: July 15, 2012, 07:10:13 AM »

Here is a good paper on lightning protection.

http://www.sbe24.org/WBA-SBE-Shows/archives/Clinic2009/Welton-Nautel-Lightning-2009.pdf

As shown, the AC power ground and the antenna coax should be tied together before the coax is routed to the station equipment. With a dedicated transmitter building this can be designed in from the start. With a house the antenna and coax is often on the side opposite the AC power entrance. This presents a problem when the coax is routed directly to the station far from the AC power entrance. Lighting charge can then flow down the coax and through the house AC power wiring to the AC service ground. Ideally the coax should be routed outside the building to the AC service ground where the coax shield is bonded. Then the coax is routed to the station.
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K1CJS
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« Reply #11 on: July 16, 2012, 06:31:07 AM »

A single point ground doesn't refer to one ground rod, it refers to one ground potential for a ground rod system.  That is why the NEC demands that all ground rods be bonded together with at least a number six cable.  Also, tower installations require their own grounding system, usually a trio of ground rods for each tower leg.  ALL of these ground rods are required to be bonded together AND to the electrical ground of the building tha tower serves.

There is no need or reason to run co-ax to the house ground rod and then to the shack.  You can install a ground rod outside the entry point of the co-ax cables to the building and bond it to the building electrical ground.  That gives you your single point ground, and satisfies the NEC requirements.  Good luck and 73!
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WX7G
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« Reply #12 on: July 16, 2012, 07:26:47 AM »

With the coax entering the building far from the AC service ground a path exists for lighting charge to flow through the AC power wiring in the building. With a number 6 wire shunting the path through the house the current through the house is reduced only by a factor of two. With the coax routed to the AC service ground first (and add all the ground rods you want between the antenna and the AC service ground, they will help) the lightning current through the house is only that which charges house wiring capacitance to ground. This is very roughly a few hundred amps.

http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf
« Last Edit: July 16, 2012, 08:00:58 AM by WX7G » Logged
WX7G
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« Reply #13 on: July 16, 2012, 08:29:00 AM »

Pages 8-10 of the IEEE guide point out the routing of cables to the AC service ground.
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K1CJS
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« Reply #14 on: July 17, 2012, 04:34:57 AM »

Two things, Dave.  You neglect to realize that the cable bonding the ground rods is secondary--each rod, properly installed, is a dissipation point for electrical charges.  The cable acts to keep the rods at the same potential--nothing more.  It is NOT intended as a path for the entirety of the charge being dissipated--not at all.

Second, that bonding cable should not be run through the house as YOU stated--unless it is unavoidable--and with a properly designed and installed grounding SYSTEM, it is never unavoidable to run a grounding cable inside the house.  Some hams--and many professionally installed sites--have a grounding halo around the building, a heavy cable with spaced ground rods that increases protection in the event of a lightning strike.

Are you seriously suggesting that a tower and everything else that may be included in a ham shack, whether it be in a home or by itself, rely on one single ground rod?  If you are, my friend, you should review tower and shack installation and set-up procedures, and not rely on your interpretation of one single article put out by the IEEE.  73.
« Last Edit: July 17, 2012, 04:46:08 AM by K1CJS » Logged
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