roth_ritter
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If one grounds the antenna shielding (as in via a Polyphaser lightning arrestor) to a ground rod near the house feed point, is it redundant to ground the receiver as well? Is this basically the same thing?
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Grounding redundancy?
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i don't know about anyone else... but my practices are that i ground the antenna to 1 rod, and my rig to a totally separate ground rod at a different location. But that is just my method and seems to work fine for me.
Grounding
Howdy
I am sure others will offer points of view, but most conventional thinking seems to be to have the grounding system tied together, as to not have different ground potential(s), thus providing a possible different current flow during say a lighting strike, etc.
This is how 'ground-grid' systems are used and most serious systems (military / telco's...) try to get below 10 Ohms (we targeted < 5 Ohms in USAF TAC Comm's) to both reduce noise levels (and COMSEC) and for safety. It was not easy to get below 10 Ohms at times,especially in dry/cold enviroments so we used multiple rods (8' type) and salt-water at times....
Simply put, take an Ohm Meter and measure between the gound(s) /rods and see what the numbers are--lower is better! I recommend gound-grid as it gives you gear better protection and the Poly's are great as well.
That's my view......
Thx
Bill
Howdy
I am sure others will offer points of view, but most conventional thinking seems to be to have the grounding system tied together, as to not have different ground potential(s), thus providing a possible different current flow during say a lighting strike, etc.
This is how 'ground-grid' systems are used and most serious systems (military / telco's...) try to get below 10 Ohms (we targeted < 5 Ohms in USAF TAC Comm's) to both reduce noise levels (and COMSEC) and for safety. It was not easy to get below 10 Ohms at times,especially in dry/cold enviroments so we used multiple rods (8' type) and salt-water at times....
Simply put, take an Ohm Meter and measure between the gound(s) /rods and see what the numbers are--lower is better! I recommend gound-grid as it gives you gear better protection and the Poly's are great as well.
That's my view......
Thx
Bill
roth_ritter
Member
Well the problem I'm having is trying to determine how to administer both types of ground. My polyphaser is going to a ground rod a short distance from the window at entry point for electrical ground. That part is ok I think. The question is the RF ground for the radio, to lower the noise floor. I don't want to be creating ground loops by sinking another, separate ground rod, but using the same electrical ground the polyphaser is using seems like not the thing I want for RF and could make it worse?
prcguy
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What you describe voilates NEC code and will probably increase damage to equipment from a lightning strike over bonding the grounds together.
Look up NEC article 810 for proper ways to ground antennas.
prcguy
Look up NEC article 810 for proper ways to ground antennas.
prcguy
bchappuie
Member
ideally I would think youwould want a single point ground system., so you may want to mount a copper bus bar close to your equipment and tie that bar via a no.2 solid copper wire to the same ground rod used by your electric service.
Do a search for Motorola R56 grounding standards. It is the most used and trusted standard for RF situations.
Motorola R56 grounding for towers and communication sites
Just one example. Get as close as you can to the R56 standard and don't listen to all of the home brew ideas. Good luck.
Motorola R56 grounding for towers and communication sites
Just one example. Get as close as you can to the R56 standard and don't listen to all of the home brew ideas. Good luck.
Here is a GREAT place to start...
http://motorola.wirelessbroadbandsu...ublic.php?id=74b2448282a9e5290e79ce7bbba93fad
http://motorola.wirelessbroadbandsu...ublic.php?id=74b2448282a9e5290e79ce7bbba93fad
roth_ritter
Member
Motorola R56 and NEC I'm sure a sound fundamental references. The problem is, for me and people like me with just a modest wire antenna strung in a tree, that tower grounding procedural references are way above and beyond any practical solution.
I mean 10 gauge copper 50-75 ft. radials with 8 foot ground rods spaced every 10 feet? Uh, no. What about the simple situations out there. Can it even be done?
For the love of god, anybody looking for a headache?
Electrical Code vs. Good RF Grounding
After reading that, my lowly Polyphaser and ground rod appears to be quite worthless.
I mean 10 gauge copper 50-75 ft. radials with 8 foot ground rods spaced every 10 feet? Uh, no. What about the simple situations out there. Can it even be done?
For the love of god, anybody looking for a headache?
Electrical Code vs. Good RF GroundingAfter reading that, my lowly Polyphaser and ground rod appears to be quite worthless.
Im not saying to do it... Get as close as you can for your application. The short answer of your question is YES, ground ALL of your equipment, NO it's not redundant.
All ground rods must be bonded together, and the station ground must be bonded to the ground at the electrical panel. Having separate grounds is an invitation to problems, and would probably result in an insurance claim being denied. R56 is a pretty tight standard, but it's overkill for a home. The NEC is reasonable, and rational for a home installation.
prcguy
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What would be worse, an antenna that is not grounded properly and when storms are approaching you disconnect it, or install some sub standard grounding that will not protect anything but you treat it as if it will?
prcguy
prcguy
n5ims
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Neither would be a good choice, but disconnecting an antenna as a storm is approaching could kill you if the first lightning strike of that storm hit your antenna or even nearby as you were disconnecting the antenna.
Remember that Lightning can strike 10 miles away from the storm so if you can hear the thunder, you're within range of a lightning strike. NWS Lightning Safety Overview
roth_ritter
Member
Ok, so say the ideal goal is to create a single ground potential by bonding the copper rod outside the window to the home AC mains ground, which seems to be the general consensus. How do you deal with the situation (which I'm sure is common) where the home AC mains ground rod is on the other side of the house?
Just a few things, not in any order.
A single ground rod is almost worthless as a safety ground (as opposed to an RF ground). The idea is to dissipate current to 'dirt', which means a fairly 'large' amount of surface area contact. That 'contact' doesn't have to be deep, just deep enough so you don't trip over it or wind it up in the lawn mower.
The National Electrical Code (NEC) is a very nice reference for grounding of all kinds (in the USA, not necessarily in other countries). It's typically the minimum standard for things (as in insurance companies?). You may not like, or agree with what it recommends, but there's a reason for it being a 'standard' (although a 'minimum' one).
The typical "spark-gap" type arrestors are NOT worth having. By the time they 'spark' to ground, the current has already gotten to what you're trying to protect, RATS!
There are a bunch more things to lightning protection, most are covered in that NEC...
- 'Doc
A single ground rod is almost worthless as a safety ground (as opposed to an RF ground). The idea is to dissipate current to 'dirt', which means a fairly 'large' amount of surface area contact. That 'contact' doesn't have to be deep, just deep enough so you don't trip over it or wind it up in the lawn mower.
The National Electrical Code (NEC) is a very nice reference for grounding of all kinds (in the USA, not necessarily in other countries). It's typically the minimum standard for things (as in insurance companies?). You may not like, or agree with what it recommends, but there's a reason for it being a 'standard' (although a 'minimum' one).
The typical "spark-gap" type arrestors are NOT worth having. By the time they 'spark' to ground, the current has already gotten to what you're trying to protect, RATS!
There are a bunch more things to lightning protection, most are covered in that NEC...
- 'Doc
roth_ritter
Member
Let me digress for a moment since my original topic has ballooned into something bigger...
I know that nothing is going to be a guarantee against a direct lightning strike. First I'm just looking for a little transient static discharge safety for the rigs. I just got a Polyphaser for this and it needs to send this charge somewhere. That somewhere is a close by 8' rod. The first task I have is to make sure that this is going to work or whether it will be a waste of time because of the ground rod not being bonded to the house mains.
Second is tackling an RF ground for the radio, but first thing is first.
I know that nothing is going to be a guarantee against a direct lightning strike. First I'm just looking for a little transient static discharge safety for the rigs. I just got a Polyphaser for this and it needs to send this charge somewhere. That somewhere is a close by 8' rod. The first task I have is to make sure that this is going to work or whether it will be a waste of time because of the ground rod not being bonded to the house mains.
Second is tackling an RF ground for the radio, but first thing is first.
prcguy
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Is this for an HF system or VHF/UHF?
I'll throw out an opinion for discussion and please don't take this as how to build your system.
My opinion is if it's an HF antenna (especially a lengthy wire) that is lower than surrounding lightning targets or otherwise unlikely to receive a direct hit, there is still a good chance the radio can be damaged from a nearby strike from induced currents in the antenna even if it has a lightning protector.
For a VHF/UHF system the antenna capture area is small and there is much less chance of a nearby strike damaging a VHF/UHF/800 radio.
I have seen many Polyphaser protected VHF and UHF repeaters that received direct hits and destroyed the antenna but the radio equipment is just fine. This is at commercial mountain top repeater sites where the grounding system was designed for lightning survival.
prcguy
I'll throw out an opinion for discussion and please don't take this as how to build your system.
My opinion is if it's an HF antenna (especially a lengthy wire) that is lower than surrounding lightning targets or otherwise unlikely to receive a direct hit, there is still a good chance the radio can be damaged from a nearby strike from induced currents in the antenna even if it has a lightning protector.
For a VHF/UHF system the antenna capture area is small and there is much less chance of a nearby strike damaging a VHF/UHF/800 radio.
I have seen many Polyphaser protected VHF and UHF repeaters that received direct hits and destroyed the antenna but the radio equipment is just fine. This is at commercial mountain top repeater sites where the grounding system was designed for lightning survival.
prcguy
ridgescan
Member
I have my HF antenna grounded to the nearby fire escape at the rooftop, which is bolted to the Ibeam structure of the 10-unit building. Then I have antenna switches equipped with surge pills and neutral switches, and those switches and all radios are grounded at the cold water pipe in the bathroom next to my radio desk. Would these be considered adequate?
KC4RAF
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Grounding should be continual.
Both Alliance01TX (Bill) and SurgePGH are correct. If you have seperate grounding that are not electrically a unit of 1, then you have chance of different potentials at the ground level. That's bad news to your equipment. Bond all grounds together.
SurgePGH gave a website that goes in detail very well about grounding:
here it is again for your information:
Motorola R56 grounding for towers and communication sites
Both Alliance01TX (Bill) and SurgePGH are correct. If you have seperate grounding that are not electrically a unit of 1, then you have chance of different potentials at the ground level. That's bad news to your equipment. Bond all grounds together.
SurgePGH gave a website that goes in detail very well about grounding:
here it is again for your information:
Motorola R56 grounding for towers and communication sites
roth_ritter
Member
As I mentioned before, I'm not dealing with a tower here and the rigorous lengths required to pull that off. I'm familiar with the Motorola R56 page and for the most part it doesn't really apply to my situation. I have a simple dipole hanging from a tree with 100' of coax, that's it. The main thing that DOES correlate is bonding the grounds together, but as I raised earlier there is a bit of a conundrum when the house AC mains ground rod is on the other side of the house. I know that must be the case in many scenarios but I haven't seen a solution.
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