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Earthing and the radio amateur

Stewart Mason
I've recently joined the IET forums. I replied to a  topic regarding amateur radio and PME on the old forum. Unfortunately I cant access the old forum anymore so I thought it would be best to start a new topic.


So. On the bench there is a transceiver with a metal case. Next to the transceiver there is a antenna tuning unit which is connected to a antenna system which is using an earth rod. Am I right in saying there is a chance of a potential difference between the two metal cases of the equipment regardless if it is a TT, TNS or TNCS?


What would be the ideal solution?  Put the shack on it's own TT supply and bond all the radio equipment back to the MET of the TT and if a earth rod is used for the antennas connect that back to the MET also?


If the TT system was not an option what would be best if the supply was a PME and you didn't want to use balanced antennas removing the use of an earth rod? 


To be honest I've never really given PME's and amateur radio much thought which in hindsight was probably a mistake. I do remember when I did my training an earth rod was recommended for the radios.


Apologies for being so random.


Stewart M0SDM
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    I also have worries about getting RF into the mains via bonding. If you don't mind the isolation transformer, this will give you the best of all worlds and you can freely connect the equipment to the RF Earth rod. The secondary of the isolating transformer will need to be made into a TN-S supply by earthing one end of the secondary to the RF earth (Earth neutral bond), and you may wish to fit an RCD to the secondary for additional safety. If the transformer has a screen connection this should connect to the RF Earth helping to prevent RF from getting into the mains supply. However you still have some degree of two Earthing systems in the shack, and bonding them together via an RF choke (wound with largeish wire and suitable ferrites) might be a good solution, or perhaps preventing contact with radiators etc with insulating cases.. Obviously the transformer must feed all the sockets in the room, again to prevent access to both Earthing systems at once. Even a 100W rig can cause TVI or network disruption over quite an area if the SWR is not good inside the shack, so the connections to the ATU and Earth rod need to be as short as possible.


    On another note, you really need to get your wire higher if possible, as the radiation angle will be very high if it is low. Verticals can be very good in this situation and can be hidden quite well, or even fitted to the Chimney with radials on the roof as the ground plane, and both can be loaded with inductors to get virtual extra length.


    73, G8FNR


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  • 0
    I also have worries about getting RF into the mains via bonding. If you don't mind the isolation transformer, this will give you the best of all worlds and you can freely connect the equipment to the RF Earth rod. The secondary of the isolating transformer will need to be made into a TN-S supply by earthing one end of the secondary to the RF earth (Earth neutral bond), and you may wish to fit an RCD to the secondary for additional safety. If the transformer has a screen connection this should connect to the RF Earth helping to prevent RF from getting into the mains supply. However you still have some degree of two Earthing systems in the shack, and bonding them together via an RF choke (wound with largeish wire and suitable ferrites) might be a good solution, or perhaps preventing contact with radiators etc with insulating cases.. Obviously the transformer must feed all the sockets in the room, again to prevent access to both Earthing systems at once. Even a 100W rig can cause TVI or network disruption over quite an area if the SWR is not good inside the shack, so the connections to the ATU and Earth rod need to be as short as possible.


    On another note, you really need to get your wire higher if possible, as the radiation angle will be very high if it is low. Verticals can be very good in this situation and can be hidden quite well, or even fitted to the Chimney with radials on the roof as the ground plane, and both can be loaded with inductors to get virtual extra length.


    73, G8FNR


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