27-07-2018, 07:19 AM
I have been told by a local ham who is knows a lot about such things, that the "rule of thumb for" ACMA inspectors when assessing antennas for EMR safety is that "no part of the antenna should be touchable."
That means, for wire antennas, a minimum height of 4m for any part of the antenna, that being twice the height of an average person. This appears to be a very sensible and practical rule of thumb.
In the case of ground-mounted verticals, a barrier must be erected around the antenna to prevent it being touched. Obviously the distance of the barrier from the antenna needs to be greater than the calculated EMR exclusion zone. Some wire mesh will do it, but a bit unsightly and maybe not XYL friendly.
Another way to deal with a vertical would be to mount it on a pole so that the base is 4m high. I am going to do this with my vertical to try and improve its efficiency anyway, but I will have to use elevated radials and the ends of those will not be 4m high. They will droop down to the level of my 2m high wooden fence and the 80m ones will run along the top of the fence. So they could be "touchable" - with some effort, but they are counter poises not radiators.
So is this still compliant?
Please be sensible and don't turn this into an ACMA bashing exercise.
73
Wayne VK4WDM
That means, for wire antennas, a minimum height of 4m for any part of the antenna, that being twice the height of an average person. This appears to be a very sensible and practical rule of thumb.
In the case of ground-mounted verticals, a barrier must be erected around the antenna to prevent it being touched. Obviously the distance of the barrier from the antenna needs to be greater than the calculated EMR exclusion zone. Some wire mesh will do it, but a bit unsightly and maybe not XYL friendly.
Another way to deal with a vertical would be to mount it on a pole so that the base is 4m high. I am going to do this with my vertical to try and improve its efficiency anyway, but I will have to use elevated radials and the ends of those will not be 4m high. They will droop down to the level of my 2m high wooden fence and the 80m ones will run along the top of the fence. So they could be "touchable" - with some effort, but they are counter poises not radiators.
So is this still compliant?
Please be sensible and don't turn this into an ACMA bashing exercise.
73
Wayne VK4WDM