14-10-2018, 07:37 AM
An addition to Terry's comments:
A MOV will effectively go short-circuit when tripped (i.e. conducts the peak current once the rated voltage is exceeded, some recover & some don't) so make sure that the rotator power supply is properly fused.
I guess also protecting the rotator is dependent on how it is mounted, and how the supporting arrangement is grounded. I have towers that have bases go 1.8 metres into the ground in what is typically damp soil with 600Kg of concrete around the 150mm NB galv mounting pipe. The Yaesu G800 rotators are mounted in a U-shape arrangement on its side (1m high) so that the GS050 thrust bearing takes a lot of the mechanical load. The rotator body is mechanically grounded to the tower to the base by what should be an effective connection, a direct strike excepted.
That all said, a direct lightning strike to your antenna arrangement is not going to be overcome easily. It will pulverise any feeder and rotator cables, and gear remotely connected together in the shack. Your rigs will likely die unless they are stored away in their boxes and not connected to anything. Consider it mass destruction.
A nearby lightning strike may cause some damage and this is the case where MOVs might help. I have my doubts about what voltage the MOVs should be because the likes of a 3-wire rotator run from about 24VAC so the suggested 460V one won't conduct until the rotator's voltage ratings are well and truly exceeded nearly 20 times. I would suggest double the typically applied voltage eg 50V for a 24V circuit. Even that might be too high.
Actually the best form of protection from lightning as far as an amateur station is concerned is a good household and contents insurance policy. Make sure all of your gear (including power supplies and accessories) is covered for replacement under the policy, ditto antennas and cabling.
Touching wood here : I have had antennas up in the air for over 50 years and no really near misses by lightning. Storms with winds strong enough to fracture a rotator housing and having the top of it plus the HF tribander fall to the house roof - that would be a yes to that. (That is why I use the U-support arrangement these days, to avoid rotator failure.)
My coaxes remain connected during storms but feed via in-line coaxial arrestors to the radios, their earth path being a very direct RG213 outer/braid to the aluminium bus bar along the back of the operating table and then to the 1.8m 'shack' earthing rod via some LDF4-50 outer (slight flexibility requirement) to get there.
PS There are 13 coax feeders coming into my shack - disconnecting all of those simply is not going to happen.
A MOV will effectively go short-circuit when tripped (i.e. conducts the peak current once the rated voltage is exceeded, some recover & some don't) so make sure that the rotator power supply is properly fused.
I guess also protecting the rotator is dependent on how it is mounted, and how the supporting arrangement is grounded. I have towers that have bases go 1.8 metres into the ground in what is typically damp soil with 600Kg of concrete around the 150mm NB galv mounting pipe. The Yaesu G800 rotators are mounted in a U-shape arrangement on its side (1m high) so that the GS050 thrust bearing takes a lot of the mechanical load. The rotator body is mechanically grounded to the tower to the base by what should be an effective connection, a direct strike excepted.
That all said, a direct lightning strike to your antenna arrangement is not going to be overcome easily. It will pulverise any feeder and rotator cables, and gear remotely connected together in the shack. Your rigs will likely die unless they are stored away in their boxes and not connected to anything. Consider it mass destruction.
A nearby lightning strike may cause some damage and this is the case where MOVs might help. I have my doubts about what voltage the MOVs should be because the likes of a 3-wire rotator run from about 24VAC so the suggested 460V one won't conduct until the rotator's voltage ratings are well and truly exceeded nearly 20 times. I would suggest double the typically applied voltage eg 50V for a 24V circuit. Even that might be too high.
Actually the best form of protection from lightning as far as an amateur station is concerned is a good household and contents insurance policy. Make sure all of your gear (including power supplies and accessories) is covered for replacement under the policy, ditto antennas and cabling.
Touching wood here : I have had antennas up in the air for over 50 years and no really near misses by lightning. Storms with winds strong enough to fracture a rotator housing and having the top of it plus the HF tribander fall to the house roof - that would be a yes to that. (That is why I use the U-support arrangement these days, to avoid rotator failure.)
My coaxes remain connected during storms but feed via in-line coaxial arrestors to the radios, their earth path being a very direct RG213 outer/braid to the aluminium bus bar along the back of the operating table and then to the 1.8m 'shack' earthing rod via some LDF4-50 outer (slight flexibility requirement) to get there.
PS There are 13 coax feeders coming into my shack - disconnecting all of those simply is not going to happen.
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.