Antenna grounding & placement

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KO4IPV

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I have the Can-Scan-III the base is the Larson High frequency magnetic mount for this antenna designed basically for mobile use but for a short time maybe a week I have it placed on my roof as a base antenna & I have it placed on a dryer vent (Metal) is this sufficiently also grounded ? Could this become a problem in bad weather Lightning? Damage to my radio !
 

prcguy

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The vent is probably big enough for a ground plane at 800MHz but not lower in frequency. For use down to VHF hi band try to keep the ground plane at least 3ft in diameter or across. Its impossible to lightning proof that type of setup and if you get a direct hit the radio will be the least of your worries.

I have the Can-Scan-III the base is the Larson High frequency magnetic mount for this antenna designed basically for mobile use but for a short time maybe a week I have it placed on my roof as a base antenna & I have it placed on a dryer vent (Metal) is this sufficiently also grounded ? Could this become a problem in bad weather Lightning? Damage to my radio !
 

mmckenna

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I have the Can-Scan-III the base is the Larson High frequency magnetic mount for this antenna designed basically for mobile use but for a short time maybe a week I have it placed on my roof as a base antenna & I have it placed on a dryer vent (Metal) is this sufficiently also grounded ? Could this become a problem in bad weather Lightning? Damage to my radio !
RF grounds and lightning grounding are two different things.

For your RF ground, the magnetic mount is capacitively coupling to the metal in the vent. Not ideal, but you are getting something. Ideal would be an NMO mount permanently installed in a metal sheet at least 1/4 wave in length in all directions under the antenna. On VHF frequencies, this would be about 38-40 inches diameter.

Lightning ground is creating a path to a ground rod. As prcguy said, it's difficult to lightning proof any sort of residential antenna install that won't result in some level of damage.
To do a lightning ground, you'd need to have the antenna base grounded directly to a ground rod under the antenna. You'd also want a lightning suppressor on your coaxial feed line where it enters the house. The ground rods need to be bonded to your homes electrical ground rod. Complex, costly and takes some design work.
 

KO4IPV

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RF grounds and lightning grounding are two different things.

For your RF ground, the magnetic mount is capacitively coupling to the metal in the vent. Not ideal, but you are getting something. Ideal would be an NMO mount permanently installed in a metal sheet at least 1/4 wave in length in all directions under the antenna. On VHF frequencies, this would be about 38-40 inches diameter.

Lightning ground is creating a path to a ground rod. As prcguy said, it's difficult to lightning proof any sort of residential antenna install that won't result in some level of damage.
To do a lightning ground, you'd need to have the antenna base grounded directly ta ground rod under the antenna. You'd also want a lightning suppressor on your coaxial feed line where it enters the house. The ground rods need to be bonded to your homes electrical ground rod. Complex, costly and takes some design work.
The NMO Mount you are referring to : I believe I can achieve this by installing a Larson BSA kit mast mount, please tell me if I am incorrect in that assumption. Will I still need a ground setup with the NMO Mount? And as far as a lightning suppressor we’re do I get one and does this go into the coax?
 

mmckenna

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The NMO Mount you are referring to : I believe I can achieve this by installing a Larson BSA kit mast mount, please tell me if I am incorrect in that assumption. Will I still need a ground setup with the NMO Mount? And as far as a lightning suppressor we’re do I get one and does this go into the coax?
The LarsEn BSA kit will provide a suitable RF ground plane under the antenna.

Grounding the antenna for nearby lightning strike safety will require properly grounding the mast the antenna is mounted on and installing something like a Polyphaser where the coaxial cable enters the home. https://www.theantennafarm.com/catalog/polyphaser-is-50nx-c2-1913
 

KO4IPV

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The LarsEn BSA kit will provide a suitable RF ground plane under the antenna.

Grounding the antenna for nearby lightning strike safety will require properly grounding the mast the antenna is mounted on and installing something like a Polyphaser where the coaxial cable enters the home. https://www.theantennafarm.com/catalog/polyphaser-is-50nx-c2-1913
Grounding the mast ! That mast would be the bracket the antenna is attached to correct ? And that polyphaser wow very expensive ! So that goes into my coax feed we’re it enters the house I think I have it if I am incorrect please inform me would appreciate all your help.
 

KO4IPV

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Grounding the mast ! That mast would be the bracket the antenna is attached to correct ? And that polyphaser wow very expensive ! So that goes into my coax feed we’re it enters the house I think I have it if I am incorrect please inform me would appreciate all your help.
And how do I make a proper ground for mast ? What are the parts and procedures
 

mmckenna

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Grounding the mast ! That mast would be the bracket the antenna is attached to correct ? And that polyphaser wow very expensive ! So that goes into my coax feed we’re it enters the house I think I have it if I am incorrect please inform me would appreciate all your help.
Right. The mast needs to be grounded.
Polyphasers are expensive, and you could probably get by with a cheaper brand. Polyphasers are common in the two way radio industry and are well respected.

The protector is placed where the coax enters the house to help reduce impact of a nearby strike.
 

KO4IPV

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Depends on the mast. You want a good electrical connection. How you do that depends on the materials used for the install.
I was intending to attach the mask and the antenna to a PVC pipe and that PVC pipe attached to the facia of my home would that be grounded that way with the PVC pipe ?
 

mmckenna

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PVC pipe is an insulator, so it's not going to do you any good to attempt to ground it. If you do use PVC pipe, then run the ground wire to the metal clamp that attaches the antenna to the pipe.
 

KO4IPV

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PVC pipe is an insulator, so it's not going to do you any good to attempt to ground it. If you do use PVC pipe, then run the ground wire to the metal clamp that attaches the antenna to the pipe.
Great got it Thankyou for your help and patience with my lack of knowledge on this subject
 

prcguy

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Here is some info on grounding antennas to the NEC. Read this several times and it should answer your grounding questions. Pay particular attention to grounding the antenna back to your house AC entry point and any ground rods you add must be bonded back to the AC entry point ground with no less than 6ga copper wire. If its a long run you must upsize the wire.


After all that if you get a direct lightning hit plan on replacing most of the electronics in your house if it doesn't burn down. Its just not practical to lightning proof any antenna on a residence unless the house and electrical system was designed for lightning from the ground up (pun intended).

I was intending to attach the mask and the antenna to a PVC pipe and that PVC pipe attached to the facia of my home would that be grounded that way with the PVC pipe ?
 

KO4IPV

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Here is some info on grounding antennas to the NEC. Read this several times and it should answer your grounding questions. Pay particular attention to grounding the antenna back to your house AC entry point and any ground rods you add must be bonded back to the AC entry point ground with no less than 6ga copper wire. If its a long run you must upsize the wire.


After all that if you get a direct lightning hit plan on replacing most of the electronics in your house if it doesn't burn down. Its just not practical to lightning proof any antenna on a residence unless the house and electrical system was designed for lightning from the ground up (pun intended).
I plan on grounding my bracket that holds my antenna to the ground. The mast will be PVC pipe only 19 in. As far as the coax I might go with the polyphaser maybe, or will be disconnecting my coax in a thunderstorm,
 

e737

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After all that if you get a direct lightning hit plan on replacing most of the electronics in your house if it doesn't burn down. Its just not practical to lightning proof any antenna on a residence unless the house and electrical system was designed for lightning from the ground up (pun intended).
Exactly! Mine isn't grounded but I do disconnect it when storms are around.. 536 sits in the attic
 
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