EMP Effect on Radio Users

[n8fgb]

As far as emp goes, my radio room is a faraday cage inside of a metal building. All of the steel panels are electrically connected to each other and grounded. The cage has two layers of wire shielding and the concrete floor is shielded as well. Even protected against knife edge propagation. I store my Goldwing motorcycle in there as well.
Most of the contacts I have made have been without any additional power. My Icom 746 and my QSO King antenna reach out with no problems. I do have a amplifier but I have never powered it up and is not even in my radio room. It was part of a package deal and it was just a little sweetener for the deal. I know it works the former owner demonstrated it for me.

How do you get RF in and out to your radios then. If you have antenna feedlines and electrical wires coming into to you room, then EMP can enter too.

 

[Captain Kilowatt]

How do you get RF in and out to your radios then. If you have antenna feedlines and electrical wires coming into to you room, then EMP can enter too.

Agreed. Anything conductive penetrating a Faraday cage can and will allow EMP to penetrate as if the cage was not even present. There are three types of EMP waves to safeguard against, E1,E2, and E3 waves and because of this EMP hardening is quite involved and the old idea of throwing your gear in a metal box and it will be fine is just wrong.

http://www.futurescience.com/emp/emp-myths.html

 

[Tallman]

How do you get RF in and out to your radios then. If you have antenna feedlines and electrical wires coming into to you room, then EMP can enter too.

When the radio room is in use the door is open and I drag the antenna cables in along with the power cables. If I'm on the air when the EMP hits all of my gear will be toast along with my motorcycle. I hope to never know if it doesn't work. Cell phones do not work in the room if the door is closed.
The antenna cables and the power cables come out and are connected to the SO-239 which go to power ground of the building and the power to the Super duty extension cord is turned off.
The door is then closed and locked. It is inconvenient but I will be able to talk and get wind therapy too.

 

[Rick330man]

That's why the Russians use tubes..

So do guitar players. Our 6L6s will be rocking. Our EL84s will be chiming. Our 12AX7s will be singing.

 

[Captain Kilowatt]

When the radio room is in use the door is open and I drag the antenna cables in along with the power cables. If I'm on the air when the EMP hits all of my gear will be toast along with my motorcycle. I hope to never know if it doesn't work. Cell phones do not work in the room if the door is closed.
The antenna cables and the power cables come out and are connected to the SO-239 which go to power ground of the building and the power to the Super duty extension cord is turned off.
The door is then closed and locked. It is inconvenient but I will be able to talk and get wind therapy too.

I had an AM transmitter site that had a Faraday cage as the main transmitter hut. It was a three tower array with the TX located in the middle at the center tower. The entire building walls, ceiling, and floor was wrapped in 1/4 inch hardware cloth screen. Besides the AM transmitter the building also housed a generator, VHF/UHF receivers and lots of audio gear as the site was part of a network and the audio program was picked up there and sent via land-line to a remote studio for when we were not carrying network programming. This helped to reduce RFI problems as well as vastly improved lightning protection. It was shielded so well that cell phones would not work when the door was closed even though you could see the cell site a few miles down the road. When using VHF or UHF hand helds to communicate from the main building out to one of the other towers you had to leave the door open or signals were real crappy if even existent even with five watts and only 400 feet between them. Even the air intakes and outlets to the building were screened.

 

[Tallman]

I had an AM transmitter site that had a Faraday cage as the main transmitter hut..

I wish I knew how to get the cables protected so I would not have to keep dragging cables in and out of the cage. It is causing some wear and tear on the threshold shielding for the door. When I did some calibrations in there, only the test leads of the scope and DVM's were allowed inside.

 

[Captain Kilowatt]

I wish I knew how to get the cables protected so I would not have to keep dragging cables in and out of the cage. It is causing some wear and tear on the threshold shielding for the door. When I did some calibrations in there, only the test leads of the scope and DVM's were allowed inside.

Redesign them to plug into a bulkhead. You would still have to connect/disconnect but at least you could just plug everything into the outside while everything remains connected to the inside of the bulkhead.That would be the best way to preserve the integrity of the cage. Our main concern was lightning protection and the towers themselves had extra protection for that. In my 22 years we only had one strike that did anything although there were MANY more I am sure. Three 222 foot towers in the middle of a field begs to be hit. I walked into the site one day and smelled burnt "something". I looked up at the meters and the RF ammeter was totally black. It blew and thankfully shorted out so it was still allowing the RF out to the tuning and phasing unit and then to the towers.

 

[Tallman]

Redesign them to plug into a bulkhead. You would still have to connect/disconnect but at least you could just plug everything into the outside while everything remains connected to the inside of the bulkhead.

That sounds like a plan. I'm going to sheet rock the cage inside and out so I can insulate it for heat and AC.