Proper grounding for Icom AH-730 tuner

[Teppka]

My setup is the Icom 7300 connected to Icom AH-730 tuner connected to endfed wire. There is a lightening arrester in the middle of the tuner and transceiver coaxial cable that grounds to the ground rod.

Now the question is where should I connect the grounding cable from AH-730 tuner, to the same grounding rod or metal roof? My understanding is AH-730 grounding connection is to eliminate RF and provide ground for the end fed antenna.

Same question to the grounding of Icom 7300 teansiver. My understanding is it needs to be ground to the metal roof to eliminate RF and not to the ground rod that lightening arrester is connected too.

Would appreciate an expert opinion.

Thanks

 

[prcguy]

Do you have a ground plane or counterpoise connected to the antenna tuner ground? That type tuner needs a significant ground plane or multiple wire counterpoise to work against which is separate from and has nothing to do with earth grounding for lightning or static. Without a counterpoise the tuner will try to use your coax as the counterpoise and that will become a radiating part of the antenna just like the antenna wire.

 

[Teppka]

Do you have a ground plane or counterpoise connected to the antenna tuner ground? That type tuner needs a significant ground plane or multiple wire counterpoise to work against which is separate from and has nothing to do with earth grounding for lightning or static. Without a counterpoise the tuner will try to use your coax as the counterpoise and that will become a radiating part of the antenna just like the antenna wire.

That was my idea, to connect a tuner ground as counterpoise with a 5m cable to the steel roof and not the ground rod.

 

[prcguy]

That was my idea, to connect a tuner ground as counterpoise with a 5m cable to the steel roof and not the ground rod.

Its recommended the counterpoise or ground plane be larger than the main antenna wire but there are many ways you can use the tuner. You could run it as a non resonant dipole with equal length antenna and counterpoise wire but you would want to use a good ferrite choke balun at the coax connector on the tuner and also use a choke balun on any control wires right at the tuner. Some people (myself included) have used the tuner at the top of a tower with a horizontal antenna wire and use the entire tower as the counterpoise if the tower mass is larger than the antenna wire. Or some (me) use a vertical whip and wires or mesh on the ground as a ground plane.

Then I see others with a tuner and long antenna wire and no ground plane or counterpoise and they usually ask why they have RF getting into the radio or why the grounded mic hangup button burns them when the transmit, etc. That would be an extreme case of the coax shield becoming a radiating part of the system making the radio, power supply, mic and everything hot.

For grounding lightning protection and human safety grounding I would suggest looking into NEC article 810 which deals specifically with antenna grounding to meet code and your ground rod could become part of that.

 

[Teppka]

Its recommended the counterpoise or ground plane be larger than the main antenna wire but there are many ways you can use the tuner. You could run it as a non resonant dipole with equal length antenna and counterpoise wire but you would want to use a good ferrite choke balun at the coax connector on the tuner and also use a choke balun on any control wires right at the tuner. Some people (myself included) have used the tuner at the top of a tower with a horizontal antenna wire and use the entire tower as the counterpoise if the tower mass is larger than the antenna wire. Or some (me) use a vertical whip and wires or mesh on the ground as a ground plane.

Then I see others with a tuner and long antenna wire and no ground plane or counterpoise and they usually ask why they have RF getting into the radio or why the grounded mic hangup button burns them when the transmit, etc. That would be an extreme case of the coax shield becoming a radiating part of the system making the radio, power supply, mic and everything hot.

For grounding lightning protection and human safety grounding I would suggest looking into NEC article 810 which deals specifically with antenna grounding to meet code and your ground rod could become part of that.

Thanks. That’s what I am planing to do, tuner will have a horizontal wire and counterpoise cable about 6m connected to an entire roof which is made of steel construction. Control cable also have a grond cable which I will connect to the both transciger and tuner. Transceiver will have the ground connection to the same roof.

I also have a power supply which I also plan to connect to the roof to avoid possible RF even though power supply is not switching.

 

[prcguy]

Thanks. That’s what I am planing to do, tuner will have a horizontal wire and counterpoise cable about 6m connected to an entire roof which is made of steel construction. Control cable also have a grond cable which I will connect to the both transciger and tuner. Transceiver will have the ground connection to the same roof.

I also have a power supply which I also plan to connect to the roof to avoid possible RF even though power supply is not switching.

Not sure if bonding everything to the roof is the best idea. The metal roof can certainly be part of the antenna counterpoise but it might be a hotbed of noise from RFI generating devices in your house. It may also complicate lightning protection if you bond the radio to the metal roof. If the antenna/roof were to get hit by lightning the radio bonding is a direct path through the radio to ground for a lightning strike. You would typically have a lightning arrestor at the coax entry point of the building that is bonded to the main building ground bringing in less lightning problems into the house from the antenna getting hit by lightning. Bonding the radio to the metal roof would bypass any lightning grounding on the feedline.

I'll go out on a limb here and say if the metal roof is part of a counterpoise, which is a radiating part of the antenna then noise picked up by the roof from computers and stuff in the house can flow to the tuner into the coax and to your radio to be received. Looking at this from another perspective, if you planted a whip antenna vertical in the center of the metal roof fed by the tuner and the tuner was bonded to the metal roof, that should pick up less noise from the roof under the same conditions because a ground plane that goes outward in all directions from the base of the antenna is not a radiating part of the antenna like the same metal roof connected to a single counterpoise wire that goes to the tuner. At least that's my opinion but based on some factual stuff.

 

[Teppka]

Not sure if bonding everything to the roof is the best idea. The metal roof can certainly be part of the antenna counterpoise but it might be a hotbed of noise from RFI generating devices in your house. It may also complicate lightning protection if you bond the radio to the metal roof. If the antenna/roof were to get hit by lightning the radio bonding is a direct path through the radio to ground for a lightning strike. You would typically have a lightning arrestor at the coax entry point of the building that is bonded to the main building ground bringing in less lightning problems into the house from the antenna getting hit by lightning. Bonding the radio to the metal roof would bypass any lightning grounding on the feedline.

I'll go out on a limb here and say if the metal roof is part of a counterpoise, which is a radiating part of the antenna then noise picked up by the roof from computers and stuff in the house can flow to the tuner into the coax and to your radio to be received. Looking at this from another perspective, if you planted a whip antenna vertical in the center of the metal roof fed by the tuner and the tuner was bonded to the metal roof, that should pick up less noise from the roof under the same conditions because a ground plane that goes outward in all directions from the base of the antenna is not a radiating part of the antenna like the same metal roof connected to a single counterpoise wire that goes to the tuner. At least that's my opinion but based on some factual stuff.

Thanks for detailed reply. Would it make sense then to not connect transiver to anything else? Tuner will have lightening arrester connected to the building ground, ground of tuber wi be connected to the metal roof as counter pose and transceiver will be connected to the tuner ground through the control cable ground wire.

 

[prcguy]

Thanks for detailed reply. Would it make sense then to not connect transiver to anything else? Tuner will have lightening arrester connected to the building ground, ground of tuber wi be connected to the metal roof as counter pose and transceiver will be connected to the tuner ground through the control cable ground wire.

If you read some NEC article 810 examples it will show an lightning arrestor in the feedline where the feedline enters the building and that would be bonded to the house AC entry panel ground with a short run of wire. If you installed any additional ground rods they would be bonded back to the house AC entry panel ground, etc. The radio can be grounded via the power supply and third prong on the AC power cord or back to the house AC entry panel ground. The tuner power/control cable connecting right to the radio is a problem and there are lightning arrestors for that. I would recommend following the NEC but just be aware its for human safety and not necessarily for lightning protection. Its almost impossible to protect from a direct strike but building to NEC should help with nearby strikes and resulting induced HV onto your antenna wire.

Its also good to RF choke the coax and control cable right at the tuner and if the coax is small like RG-58 or 8X you can wrap 9 turns of coax through an FT-240-31 ferrite toroid. If you can also fit 9 turns of the tuner control cable through the same toroid great or get another just for the control cable. That will isolate the antenna, tuner and cables from the radio and help reduce RFI from riding up the coax or control cable to the antenna then getting received by the radio. Or buy a good commercial common mode choke for the coax but a ferrite core is about $9 and a good commercial choke with coax connectors can cost $90 or more.

 

[Teppka]

If you read some NEC article 810 examples it will show an lightning arrestor in the feedline where the feedline enters the building and that would be bonded to the house AC entry panel ground with a short run of wire. If you installed any additional ground rods they would be bonded back to the house AC entry panel ground, etc. The radio can be grounded via the power supply and third prong on the AC power cord or back to the house AC entry panel ground. The tuner power/control cable connecting right to the radio is a problem and there are lightning arrestors for that. I would recommend following the NEC but just be aware its for human safety and not necessarily for lightning protection. Its almost impossible to protect from a direct strike but building to NEC should help with nearby strikes and resulting induced HV onto your antenna wire.

Its also good to RF choke the coax and control cable right at the tuner and if the coax is small like RG-58 or 8X you can wrap 9 turns of coax through an FT-240-31 ferrite toroid. If you can also fit 9 turns of the tuner control cable through the same toroid great or get another just for the control cable. That will isolate the antenna, tuner and cables from the radio and help reduce RFI from riding up the coax or control cable to the antenna then getting received by the radio. Or buy a good commercial common mode choke for the coax but a ferrite core is about $9 and a good commercial choke with coax connectors can cost $90 or more.

I live in a multi story building and not in the US. So grounding is a little more complicated. I’m using RG213 coaxial cable, so wrapping it around anything is out of question. I may use snap-on toroids if necessary though. Total length of coaxial cable is 8m, so I think maybe I would not even need common mode choke.

AH-730 control cable has separate cable to connect ground tuner to ground radio. I think I will not be connecting it yet then and see if I will have RFI first.

Now the main question would be to connect radio ground to the roof or not to ground at all. Connecting it to the same ground rod with lightening arrester seems to be calling for trouble.

 

[Teppka]

If you read some NEC article 810 examples it will show an lightning arrestor in the feedline where the feedline enters the building and that would be bonded to the house AC entry panel ground with a short run of wire. If you installed any additional ground rods they would be bonded back to the house AC entry panel ground, etc. The radio can be grounded via the power supply and third prong on the AC power cord or back to the house AC entry panel ground. The tuner power/control cable connecting right to the radio is a problem and there are lightning arrestors for that. I would recommend following the NEC but just be aware its for human safety and not necessarily for lightning protection. Its almost impossible to protect from a direct strike but building to NEC should help with nearby strikes and resulting induced HV onto your antenna wire.

Its also good to RF choke the coax and control cable right at the tuner and if the coax is small like RG-58 or 8X you can wrap 9 turns of coax through an FT-240-31 ferrite toroid. If you can also fit 9 turns of the tuner control cable through the same toroid great or get another just for the control cable. That will isolate the antenna, tuner and cables from the radio and help reduce RFI from riding up the coax or control cable to the antenna then getting received by the radio. Or buy a good commercial common mode choke for the coax but a ferrite core is about $9 and a good commercial choke with coax connectors can cost $90 or more.

Would it he a good idea to connect ground of IC-7300 to a ground of Diamond GSV-3000 power supply unit located on it’s back? Power supply unit is grounded through the power socket to the building electric grid ground so I assume it would provide ground connection to IC-7300 through the power supply unit.

 

[prcguy]

Would it he a good idea to connect ground of IC-7300 to a ground of Diamond GSV-3000 power supply unit located on it’s back? Power supply unit is grounded through the power socket to the building electric grid ground so I assume it would provide ground connection to IC-7300 through the power supply unit.

Many power supply 12v outputs are floating from the power supply case and AC side ground, so bonding the radio chassis to the power supply chassis should place the radio at ground potential.

The antenna the way you will be using it and the radio do not need any grounding to operate and grounding will not improve radio or antenna performance. In this case the grounding would be for safety and to give induced voltage on your antenna wire from a nearby lightning strike a path to ground. Not being in the US you do not have to build to NEC standards but you should build to meet you local electrical codes if any.