Grounding question on indoor vertical

[KC4KLM]

Hello Gentlemen.

Newer ham here. I searched around but did not get a solid answer on this.

I have an attic-mounted Diamond X50a that is fed with LMR400 down to the second floor of my house. It has worked very well for me so far. I am not experiencing any noise or hum currently (although I did have some RF interference on 70m from a LCD monitor that I have pretty much controlled).

While it isn't a lightning concern, I would like to hear from someone more experienced as to whether I need to ground this antenna from a RF signal perspective or a safety perspective.

Many thanks

 

[KF5LJW]

Do you ground Rabbit Ears antennas indoors? No, you would not ground any indoor antenna; it serves no purpose. Move that antenna outside; now, you must route the coax to the AC Service and bond the coax shield and ADU to the AC service ground before it enters the house. That protects you from lightning and utility high voltages.

 

[KC4KLM]

Thank you, KF5LJW. We don't use rabbit ears and haven't needed them in 40 years. HOA neighborhood, no outdoor antennas allowed, and outdoor usage was not the question. My antenna is 35' AGL and works beautifully where it is. I have been reading up on grounding, ground planes, and radials and am trying to learn more.

 

[nd5y]

VHF and UHF base antennas don't need an earth ground for RF. That's what the radials are for on an antenna like the X50A. Indoor antennas are as much of a lightning hazard as other metal objects like electrical wiring, plumbing and HVAC ducts.

 

[KC4KLM]

VHF and UHF base antennas don't need an earth ground for RF. That's what the radials are for on an antenna like the X50A. Indoor antennas are as much of a lightning hazard as other metal objects like electrical wiring, plumbing and HVAC ducts.

Thank you for your reply.

 

[KF5LJW]

VHF and UHF base antennas don't need an earth ground for RF. That's what the radials are for on an antenna like the X50A. Indoor antennas are as much of a lightning hazard as other metal objects like electrical wiring, plumbing and HVAC ducts.

All of them are properly grounded by their AC Equipment Grounds. Your radio is powered by an AC-powered DC 12-volt power supply, which has an AC equipment ground that grounds the radio chassis via a DC negative conductor. There is no requirement to ground an antenna in the attic. Look around at all the HDTV indoor TV antennas sold. You can not ground any of them because it serves no purpose. The TV takes care of it with its 3-wire power cord.

Your electrical wiring, plumbing, and HVAC are outside and exposed to the elements, and the NEC has very strict guidelines for everything, including ham radio. An indoor antenna is not exposed.

If you are a ham, you had better run a ground wire from your WiFi antenna to the AC service ground to protect yourself.

 

[mmckenna]

While it isn't a lightning concern, I would like to hear from someone more experienced as to whether I need to ground this antenna from a RF signal perspective or a safety perspective.

Many thanks

Sometimes people forget that a direct lightning strike is not the only concern. Even a nearby strike and induce a lot of energy into nearby antennas, masts or wiring.

Sticking a big metal thing up in your attic can be an issue. The thin layer of roofing material won't stop a lightning bolt that has traveled thousands of feet through the air (air is a pretty good dielectric). It also isn't going to magically stop induced energy from that nearby strike.

Adding a lightning protector on your coax and properly grounding it and the mast is a pretty good plan. Also, having everything at the same ground potential, and not relying on the DC ground from your radio, through the power supply/user, to a little 14 gauge wire that daisy chains through the other outlets in your home, is a good idea. Proper grounding may not address any RFI issues you have, but from a safety standpoint, it's the right thing to do.

 

[KC4KLM]

Sometimes people forget that a direct lightning strike is not the only concern. Even a nearby strike and induce a lot of energy into nearby antennas, masts or wiring.

Sticking a big metal thing up in your attic can be an issue. The thin layer of roofing material won't stop a lightning bolt that has traveled thousands of feet through the air (air is a pretty good dielectric). It also isn't going to magically stop induced energy from that nearby strike.

Adding a lightning protector on your coax and properly grounding it and the mast is a pretty good plan. Also, having everything at the same ground potential, and not relying on the DC ground from your radio, through the power supply/user, to a little 14 gauge wire that daisy chains through the other outlets in your home, is a good idea. Proper grounding may not address any RFI issues you have, but from a safety standpoint, it's the right thing to do.

Good points and makes sense. Seems as though there isn't going to be one agreed-upon standard practice on this, and that is ok.
Thank you for the helpful reply.

 

[mmckenna]

Good points and makes sense. Seems as though there isn't going to be one agreed-upon standard practice on this, and that is ok.
Thank you for the helpful reply.

Yeah, I prefer to err on the side of caution. There's a lot of well documented cases of damage from induced energy from nearby lightning strikes. I've seen it happen at work.