electromagnetic pulses - something to worry about?

[af0h]

I've got 2 sets of TCS's - WW2 Collins Transmitter/Reciever sets. Also, a GRC-9 = Korean War era backpack rig with the hand-crank generator used to power it. Yes, i'm a Ham Radio operator.

If something like this (EMP) were to happen, there would still be a few of us able to communicate with the rest of the world...

Everyone's highly priced Cell Phones = completely 100% useless at that point. Yet a few of us Ham's could still get by on the air like we do every day.

New technology doesn't always mean better technology. Transistors are a Fad, Tubes are here to stay.
And Yes, good ole Morse Code still works fine when other communication modes can't / won't work.

 

[Win]

Originally Posted By: Quest


Bad news is, over 98% of the electronic goods, from your ipod to PC to anything that runs on solid state or IC will be dead with just roughtly 3~30mV pulse;


I think you may be off by many orders of magnitude here. I just disconnected my Yagi, put a scope on the coax set to read DC, and watched quite a few .20 volt pulses (+ and -) as part of the normal background noise level here, and it's not even night yet.

Originally Posted By: Quest


recall that during the late stages of cold war: Adericans found a means of confiscating a Mig-21 fighter plane, and inside there were portions of the controlling module that was still running on tubes (ditto with some of the Soviet tanks which runs on a rugged 6C33c) that can withstand several volts of EMP during a nuclear blast......



It's more likely that their semiconductors were even junkier than their tubes, particularly for a 60's era airplane, and they just didn't have any solid state devices that could reliably function as a servo amplifier or pulse amplifier.

I doubt this was out of any concern for EMP.

 

[Win]

Originally Posted By: af0h
I've got 2 sets of TCS's - WW2 Collins Transmitter/Reciever sets. Also, a GRC-9 = Korean War era backpack rig with the hand-crank generator used to power it. Yes, i'm a Ham Radio operator.

If something like this (EMP) were to happen, there would still be a few of us able to communicate with the rest of the world...


Glad to hear you have a crankset. I have quite a bit of Collins tube gear still in service myself, and power for them is my biggest concern. I keep my generator in a steel building, but I don't know if that will be enough. All my DC-DC supplies are transistorized.

I guess I should build a faraday cage big enough for the generator and a few hand held radios, and park the SteppIR on 14 MHz, since I know its control logic would be toast.

73

 

[Shannow]

Originally Posted By: JetStar

I have seen some articles on non-nuke generated EMP being used as a weapon. I also saw something about the cops using a device in the future that will zap an automotive ECU to stop a car chase. I'm a little concerned about the selectivity of this device.


There's been reports that such as you describe have already been deployed.

 

[af0h]

Originally Posted By: Win
Glad to hear you have a crankset. I have quite a bit of Collins tube gear still in service myself, and power for them is my biggest concern.

73


Yeah, powering them could be a problem. Not sure how my generator would fare. I do have a 12v Dynamotor for the TCS's, but even 12v could be a challenge.

73

 

[Oldmoparguy1]

You don't need a nuke to get a serious EM pulse. A nearby lightning strike will do nicely. I've experienced 2, one back in Michigan where I grew up, and one here in Charlotte.

 

[Quest]

Originally Posted By: Win

I think you may be off by many orders of magnitude here. I just disconnected my Yagi, put a scope on the coax set to read DC, and watched quite a few .20 volt pulses (+ and -) as part of the normal background noise level here, and it's not even night yet.

It's more likely that their semiconductors were even junkier than their tubes, particularly for a 60's era airplane, and they just didn't have any solid state devices that could reliably function as a servo amplifier or pulse amplifier.

I doubt this was out of any concern for EMP.



well, I'm not clear/sure as to why you set a scope to read DC off of your yagi antenna? What does that supposedly tell you (enlighten me plse)?

Yes, it may seemed that I'm out of the context here RE: crummy solid state devices in the 60s or 70s but truth is, while transistors are quite well build nowadays than what it used to be in the 60s, but the fact of the matter is, unless it's "hardened", otherwise, common consumer grade electronics still cannot handle up to a couple of volts of EMP (remember this: this is an electromagnetic pulse of broad spectrum and high energy pulse, not just your average RF background noise up in the air).

Q

 

[Quest]

Originally Posted By: Oldmoparguy1
You don't need a nuke to get a serious EM pulse. A nearby lightning strike will do nicely. I've experienced 2, one back in Michigan where I grew up, and one here in Charlotte.



Yes, lightning is a nice form of naturally-occuring EMP...

 

[MolaKule]

Quote:
Are electrical equipment really at risk from something like this? and would all electrical stuff be? or just some? would a fridge still work, but a computer be fried?


The Electromagnetic Pulse (EMP) from a high altitude nuclear burst has been under investigation since 1945. The burst produces an EM wave pulse that can reach up to 15 kV/meter in strength near the burst.

The best paper I have read on the effects of EMP on power systems was the one by Dr. Rabinowitz (DRR). The conclusion was that for a 400km altitude burst with 1.4MT fission yield over the central US, less than 10% of the US power grid would fail. One of the other points made was that localized thunder storms producing lightning strikes create faster rising EM pulses than does an EMP itself, and yet the grid survives these intense and multiple strikes very well.

The major concern to the power grid IS NOT EMP but sabatoge by terrorist sleeper cells.

Most AC filter strips have MOVS in them that will take out minor surges, but I prefer to add bipolar transorbs between the hot side, Neutral and ground for extra protection. And many circuit boards and power supplies have some transient protection as well.

The bottom line is that if you have a good power strip or Service Box with breakers, or fuses, MOVS, and transorbs, then much of the transient energy can be mitigated. So it is the power supply end of circuits that need protection.

And tube gear IS susceptible to EMP or lightning as well. Can you think why this would be the case? Hint: Think in terms of the filament circuit.

If the power transient is absorbed or shunted to ground, then IC's and discreet devices such as transistors or diodes are safe.

What affects IC's and discreet devices are primarily nuclear particles (such as neutrons) hitting bipolar and mosfet junctions. This causes a charge upset which may bias the transitor beyond or out of its proper operating range.

Recently, the civilian avionics industry had been experiencing memory problems with embedded mircoprocessors and memory chips. Most of these devices are made of MOSFET digital technology such that gate-charge changes (ion-tracks) can be devistating. Since the current generation of civilian and business aircraft fly at high altitudes, it was discovered that Neutron Single Event Upsets from high altitude Cosmic-Rays were the cause of this radiation. So the manufacturers of these chips are using similar radiation hardening techniqies that we used during the cold war.

 

[MolaKule]

BTW, the STARFISH nuclear tests done in the Pacific did not cause the failure of street lights in Hawaii. This was a much overblown event. Old technology carbon charge dissipators were the cause of the 30 street lights to go out.

According to Congressional testimony at the time, by the General in charge of the test, Burglar Alarms did go off in Hawaii. However, it wasn't determined if it was the EMP or seismic vibrations that were the cause.

 

[Win]

Originally Posted By: MolaKule


And tube gear IS susceptible to EMP or lightning as well. Can you think why this would be the case? Hint: Think in terms of the filament circuit.


Heater to cathode shorts, or, for spiral filament tubes, I suppose one or more turns could short.

 

[MolaKule]

Quote:
The conclusion was that for a 400km altitude burst with 1.4MT fission yield over the central US, less than 10% of the US power grid would fail.
That paper by DRR was published in the IEEE in 1987.

That should read, "The conclusion was that for a 400km altitude burst with 1.4MT fusion yield over the central US, less than 10% of the US power grid would fail."

If an EMP pulse could couple itself into the grid, this would cause an increase in the line voltage and cause a current surge as well. This increase in voltage would cause filaments to see an increased voltage and potentially burn out, whether it be incandescent lamps or Ham Radio Tube gear. Again, devices such as transorbs or the bi-directional Overvoltage Transient Suppressors can mitigate this pulse.

Some devices that come to mind are the LittleFuse series

http://pdf1.alldatasheet.com/datasheet-pdf/view/70912/LITTELFUSE/15KE68.html

and the NTE49XX series.

Fast fuses and Metal Oxide Varistors are good for long (slow) rise-time surges, but bi-directional Overvoltage Transient Suppressors are much faster.

For the breaker Box, a device such as the Intermatic Panel Guard has been found useful for lightning and EMP.

A low altitude Nuke burst is going to cause more concerns that EMP.