>  AIS is not using the same protocol as Packet ax.25.
Correct. AX.25 is primitive and long in the tooth. In computing terms, it's a relic out of the Cro Magnon era.

> Also all of AIS is over water not land like APRS so propagation is defendant as well.
I'm plotting vessels with AIS that are on the other side of the Santa Cruz mountains, while I'm in a mountainous valley where even FM broadcast is barely receivable.  I have an APRS receiver (Kenwood D710) with an identical antenna, at exactly the same height on the same mast that hasn't even comparatively 10% the range to APRS targets - some of which are blasting 50 watts. AIS is 25 watts for "Class A" and 2.5 watts for "Class B".

It's the protocol that's bad - not the propagation. We Hams should be able to do better.

It's amazing how much better the Maritime Automatic Identification System (AIS) works - at nearly the same frequency (160 MHz) and with only 25 watts of power.

Here's the range of my AIS receiver: Reception distance in nautical miles: Average: 54.64 / Max: 264.36 (those are ephemeral stats based on the current positions of vessels - but they are typical).

You can see my stats here: http://www.marinetraffic.com/ais/stationdetails.aspx?station_id=595

And my coverage area here: http://www.marinetraffic.com/ais/default.aspx?zoom=7&centerx=-122.4805&centery=37.50246&oldmmsi=595

I also find HF APRS on 30 meters is about twice as reliable, based on packet loss rations, than VHF APRS.

My conclusion: VHF APRS doesn't work anywhere near as well as it could. And it isn't due to packet transmission frequencies: large ("Class A" AIS) vessels transmit position reports every 2 seconds. The problem with APRS is it's near complete lack of control over transmission contentioning.

I have a 26 foot sloop that I operate on the northern Pacific coast. Both the fore and back stays are about 35 feet in length. I currently am using a delta V loop (using the entire rig of standing rigging), which tunes well all the way down to 160 meters, but the radiation efficiency is low below 30 meters, and the takeoff angle isn't optimal. The stays are too short to use an insulated backstay arrangement.

So I'm starting to experiment with a kite-lofted antenna. In my area, there's plenty of wind, and I should have no trouble getting it to 200 feet. The kite anchor line is copper wire, instead of string, and for a ground plane I can trail another copper line behind the boat. My goal is to get a 5/8 wave antenna lofted for 80 meters (about 170 feet). I can "tune" the antenna by changing its length.

Has anyone else tried this? And suggestions? Naturally, I'll avoid repeating Ben Franklin's experiment during thunderstorms.

I don't even have an inverter, and still  the QRM from inverters and switching-mode DC chargers at my marina (my HF rig is aboard a sailboat) is so high that the HF band is unstable. I have a massive L/C power conditioner, but I see S20 all across the MF/HF bands. The QRM is worst around 2 MHz. Most of the noise is conveyed in through my shore power connection, but even after unplugging and stowing the shore power cable, I'm barely able to receive WWV and local AM stations.

Apparently there are no FCC noise requirements for these devices. Spark gap transmitters were banned long ago because they are "all band" transmitters. I wish the FCC would look into this source of band pollution.

It wasn't very long ago, while I was performing an information security assessment, that the IT Director proudly walked me into his: "TEMPEST proof, faraday shielded, server room." As I was standing there looking around, his cell phone rang. While he talked on the phone, I glanced at my cell phone and saw that I also had service.

When he finished his call, I pointed at the "one bar" on my cell phone display and asked him: "what's wrong with this picture?"  IT geeks seldom know much about RF, and he needed a detailed explanation. If your cell phone works inside, it's not a very good faraday shield.

The best "live aboard" faraday shield I've seen so far supplied AC power with a motor connected to the commercial power on the "outside" -- coupled through a big wooden pole to an AC generator on the "inside". The only bridge in the "air gap" was the mechanical coupling through that hunk of wood.

Unless one is in a grave situation of immediate distress with absolutely no other way to call for help, I'd stay off the marine VHF channels (channel 16, 156.800 MHz, is the calling and distress frequency). Technically, one can get a "portable" marine radio station license (I have one: WDF2783), but I'm not allowed to use it unless I'm at least sitting on something that's floating (or sinking...).

I am not aware of any restrictions on using the Ham bands as a licensed Ham operator while at sea, but technically one shouldn't be operating "uncertified" radios on the maritime channels except where there is no other means of calling in a distress situation. I enjoy listening to the checkins and weather reports from multiple Hams at sea on the Pacific maritime-mobile radio net most evenings (in California) on 14.300 MHz SSB.

Now, UNLICENSED use of the Ham bands at sea is a different story... I take a dim view of that. I've talked with some blue water sailors who are under the false perception that they can use the Ham bands without a license while in international waters. Any ship that is registered in the U.S. is still governed by FCC rules, AND international treaties, anywhere on the high seas. I'm also a Global Maritime Distress and Safety System Operator/Maintainer, and that point was stressed in my training. You can't escape your nation's regulations - unless you plan on flying the Jolly Roger. Unlicensed operation on the Ham bands makes the operator fair game to any navy that happens along - just like any other form of piracy. I've wondered if our constitutional rights to citizen's arrest allows private parties to seize a bozo's unlicensed Ham gear off a U.S. registered vessel while at sea. There have been a few drunken maritime diatribes and singing contests that I would have enjoyed interrupting. Any maritime lawyers here with an opinion?

If you're considering maritime radios as a backup plan after an EMP event - the commercial grade radios will probably be only useful as anchors.

(quoting)
Belenko: Belenko: First of all American super-market, my first visit was under CIA supervision, and I thought it was set-up; I did not believe super-market was real one. I thought well I was unusual guest; they probably kicked everyone out. It's such a nice, big place with incredible amount of produce, and no long lines! You're accustomed to long lines in Russia. (snip)


Belenko has obviously never seen the check-out lines at my local Safeway ;-)

John, Kartina certainly DID show us how ineffectual the government can be, and how much we are truly on our own in a large scale catastrophe.  To their credit though, the government itself has told us repeatedly to be prepared for self-sufficiency and to not expect prompt assistance.

I agree that our military will certainly retain some retaliatory capabilities. But if the attack follows a 9/11 scenario, then who do we retaliate against? While military command, control and communications will probably be only disrupted - not disabled, I have a much more pessimistic expectation of the post-attack intelligence capabilities. After 9/11, the FBI had photos of the perpetrators on our TV screens within hours. But after an EMP attack, the disruptions may prevent identifying the culprits. If we lash out at "all the usual suspects", we may very well be playing into the hand of the attackers - who are likely in my mind to have visions of a post-apocalyptic Utopia. Something like: "Revenge of the Luddites" (http://en.wikipedia.org/wiki/Luddite) where we are all supposed to live harmoniously in a simpler (and much less populated) world, governed by insert-fundamentalist-religion-here laws or overly-simplistic economic model. (In other words, where the Bad Guys are firmly in charge of everything.) Some societies feel very threatened by the "cultural pollution" brought on by Western communications and transportation technologies - which a NEMP will quite effectively shut down - and we won't be helping our own cause by further facilitating that apocalypse. Shutting down any legitimate government's ability to suppress these people near or within their own borders isn't going to help. I just don't see any wisdom in dropping "buckets of instant sunshine" over the stratospheres of those countries. I fear we'd likely find ourselves at a diplomatic impasse, and worse, I suspect the Bad Guys know that.

I also have to ask myself what kind of society we would have - where only the military retains the ability to communicate. Past societies haven't exactly flourished under that model.

I agree with AA4HA: The attackers will get the greatest result by launching a "one two punch"  attack: zap us once, wait for us to dig our spares out of storage, and then zap us again. So even if there is no warning, grabbing your gear (working or not) and shoving it in your oven at home (a fairly effective shield that everyone has near at hand) immediately after an EMP attack, and waiting as long as possible to remove it, might leave you with either working gear, or at least something that can be repaired. A microwave oven offers fairly good shielding for smaller VHF/UHF HTs. Don't believe me? Toss your cell phone in the microwave oven (BUT DON'T TURN THE MICROWAVE ON!) and watch through the window as it switches to "no service". Switching the oven on may be a reasonable simulation of the effects of an EMP, which will probably cause the phone to display "no service"... permanently. Don't try that experiment on anything you ever intend to use again.

To the poster here that surmises all this is just a Right Wing plot: none of the political players have control over the laws of physics. I concede that the effects have been exaggerated at times. In the book "One Second After", ALL of the late model cars quit running - even though the Commission report (referenced above in this thread) found that most of the cars they tested either continued to run, or could be immediately restarted (though you might have to suffer through some annoyance like the windshield wipers running continually). However, if you've got an antenna stuck in the air that connects to a commercial grade solid state radio - it's probably gonna get toasted.

If I were to stockpile anything, it would be the most popular transistors used in receiver front ends (wrapped in aluminum foil). That, a butane soldering iron, and some rosin core solder will be worth much more than its equivalent weight in gold.

Excellent suggestions! What keeps the bad stuff (EMP) out, also keeps the bad stuff (RFI/EMI) in. The same is true for computer security: good TEMPEST* countermeasures also provide some good EMP/RFI protection.

Here are some other ideas: You can get very high quality and extremely durable aluminum foil from a company that sells it for radiant barriers in home construction: http://www.radiantguard.com/. The heavier "Ultima" product is practically impossible to tear by hand and is perforated to prevent it from forming a vapor barrier (which would soak your gear in a humid environment). The perforations also make it much easier to apply to surfaces using adhesives (no bubbles). You can get 500 square feet of it for about $75. A thin flat conductor like foil is just as conductive to RF as a much thicker material due to skin effect, and a wide flat conductor like foil has very low effective series inductance.

Many formulations of tinted glass are conductive on the tinted side. The tinting in the form of various conductive metals is electrically sputtered onto the tinted side in a vacuum chamber. Verify conductivity of the surface with an ohm meter. You can typically find tinted glass that's 30 ohms or less between opposite corners (of any size) of a square sample. You can use conductive tape with conductive adhesive such as 3M 1120 (aluminum) or 3M 1181 (copper) for edge connections.

Tisha, you make an excellent point: The measures taken to mitigate an EMP event are really just refinements to good engineering practice. Whatever one does to improve EMP survivability pays off in everyday benefits of reduced RFI/EMI emissions and improved survivability from lightning and power line transients.

I have often heard Hams talk about the futility of providing enough protection to allow their gear to survive a direct hit from lightning. When I was the assistant chief engineer at KLMS AM in Lincoln, NE, I would sometimes watch lightning split into five forks and strike all five of our towers simultaneously. It made some really loud snapping sounds and left the transmitter building smelling like ozone, but we would take dozens of direct hits every year with only rare damage to either the transmitter or co-located studio. We just followed good practices: a really good single point "common" ground and careful bonding of everything to that ground by the shortest possible path using adequately large flat conductors. All that effort paid off in terms of lowered noise and hum in our audio, and we escaped the problems that less well-engineered stations had of picking up taxi and police calls in their audio gear.

The same is true of EMP protection: it's not futile, and a small amount of effort and materials can go a long way toward mitigating the effects, while providing every day benefits.


* The NSA recently declassified TEMPEST - see this link: http://www.nsa.gov/public_info/_files/cryptologic_spectrum/tempest.pdf. (And no, you won't have black helicopters hovering over your home after accessing the link). Since it involves RF and spycraft, the topic should be interesting to some Hams.

If anyone would like to test the survivability of their own radios, there is now an outfit that is selling plans and parts for creating your own mini EMPs. Hopefully, they don't work as well as claimed...

http://www.amazing1.com/emp.htm

I'd write about all the nasty things one could do with one of those, but it'd be irresponsible.

True. It would be a mess of biblical proportions that would make the loss of life during the Black Plague look like a minor flu outbreak. And I suppose some people would throw in the towel, in which case, a 45 caliber pistol and a single cartridge would be sufficient "preparations."

I don't think most Hams would give up that easily. As long as you can read a schematic, and know how to replace/swap fried semiconductors, you'll have plenty of employment. And you may be able to trade a working radio for a horse.  

I don't mean to make light of the situation. Anyone who's toured a food processing plant will appreciate how automated they are - and all of that automation will probably stop working. Our society is unimaginably vulnerable to a prolonged loss of technology. But if such an attack should ever occur, we'll need two things to reboot our society: communications, and information on how to fix what's broken and cope with conditions in the meantime. The two most valuable local resources could be the neighborhood Ham and the local library.

I installed an add-on kit to run my Generac 4583 on propane (and if needed, natural gas). The kit was simple and included a duel fuel carburetor.

Send me an email (my address is registered here), and I will send you a full set of photos and specs.

I made several other modifications to the Generac, including an add on oil cooler and oil cooler thermostat for operation in hot environments (Houston).

The kit I purchased allows "hot switching" between gasoline and propane, and I added a vacuum sensor to detect exhaustion of propane that can automatically switch back to gasoline to permit changing the propane tank without an interruption in service (measuring the amount of fuel remaining in a propane tank isn't straightforward).

WARNING: NEVER attempt to add gasoline to a hot or running generator! The exposed exhaust system on my Generac glows cherry red under full load and gets as hot as 1,400 degrees F (measured with an IR thermometer) -- gasoline fumes ignite at less than 500 degrees. It will ruin your day if the fumes ignite while you're standing there with a gas can in your hands and the uncapped fuel tank contains mostly explosive fumes... One gallon of gasoline has the explosive potential of many pounds of dynamite. One other word of caution: although the exhaust fumes from propane smell benign (as opposed to the stink from gasoline), even with the best possible fuel to air mixture, the carbon monoxide concentration from the exhaust is 1% -- many times the lethal concentration. Don't breathe the fumes or operate the generator in an enclosed space where the fumes might be trapped.

Propane is by far the safest way to go.

On the topic of the likelihood of an EMP attack, please see the article at:

http://www.wnd.com/news/article.asp?ARTICLE_ID=43956

Quoting an excerpt from the above:

"Iran is not only covertly developing nuclear weapons, it is already testing ballistic missiles specifically designed to destroy America's technical infrastructure, effectively neutralizing the world's lone superpower, say U.S. intelligence sources, top scientists and western missile industry experts.

The radical Shiite regime has conducted successful tests to determine if its Shahab-3 ballistic missiles, capable of carrying a nuclear warhead, can be detonated by a remote-control device while still in high-altitude flight.

Scientists, including President Reagan's top science adviser, William R. Graham, say there is no other explanation for such tests than preparation for the deployment of electromagnetic pulse weapons – even one of which could knock out America's critical electrical and technological infrastructure, effectively sending the continental U.S. back to the 19th century with a recovery time of months or years."

A very interesting historical video documentary on EMP and EMP testing by the US military, codenamed TRESTLE and located at the Kirtland Air Force Base, can be viewed at:

http://www.ece.unm.edu/summa/notes/trestle_movie.html

If the threat model is a terrorist group, I completely agree: an EMP attack is not a likely scenario.

When performing threat modeling in my field, we often refer to the MORE Model: Motivation, Objective,  Resources, and Experience. The current crop of terrorists (Al Queda, et al) are motivated by a fundamental hatred of our culture - not by the traditional motivations of nation-state conflict: prestige, domination, and material gain. Their objective is to kill as many people as possible in as horrific a manner as possible in order to damage what they perceive to be our greatest cultural weapon: our economy, which is highly dependent on the optimistic belief in continuous growth. And part of the psychological effectiveness of their attacks has been their technical simplicity - it's not hard to learn how to steer an airplane into a building - which fosters the impression that there could be a potential terrorist hiding in every shadow. That simplicity also diminishes the likelihood of detection. The resource challenges for carrying out an EMP attack are severe, and I agree make an EMP attack by a terrorist organization very unlikely. But beyond the challenge of obtaining fissile materials, constructing a crude device with low yield would not have been beyond the abilities of the 9-11 terrorists - some of whom were degreed engineers. Constructing a radiation dispersal device ("dirty bomb") would be even simpler. The psychological impact and the resulting impact on our economy from the perception that Al Queda has "gone nuclear" would be so extreme that they're hard to imagine.

It's my own belief that the treat from an EMP attack is currently limited to the resources of a nation-state, although that doesn't rule out the possibility of a nation-state using a terrorist organization as a proxy. The motivation for nation-state to carry out such an attack is quite high: they may believe that they can capture all of our natural resources undamaged, while thwarting a retaliatory strike by concealing the origin of the attack - the forensic evidence would evaporate along with the computers that contained it.

I believe you are correct in presuming that lightning protection would be beneficial in protecting equipment from the "E2" pulse. And the Commission report agrees with that presumption. But as for the initial E1 pulse, the Commission concluded (referring specially to aircraft systems): "The frequency composition of lightning and EMP differ enough so that lightning protection does not ensure EMP protection." That conclusion is consistent with all of the research I have seen in the past 40 years of my own interest in the topic. There are few lightning protection systems that are capable of shunting a 1 nanosecond rise-time pulse.

The Commission reported that: "The early time EMP, or E1, is a freely propagating field with a rise time in the range of less than one to a few nanoseconds. E1 damages or disrupts electronics such as the SCADA, DCS, and PLC as well as communications and to some extent transportation (necessary for supplies and personnel). This disrupts control systems, sensors, communication systems, protective systems, generator systems, fuel systems, environmental mitigation systems and their related computers, as well as the ability to repair. SCADA components, in particular, are frequently situated in remote environments and operate without proximate human intervention. While their critical electronic elements are usually contained within some sort of metallic box, the enclosures’ service as a protective Faraday cage is inadequate. Such metallic containers are designed only to provide protection from the weather and a modicum of physical security. They are not designed to protect the electronics from high-energy electromagnetic pulses, which may infiltrate either from the free field or from the many antennae (cable connections) that compromise electromagnetic integrity." [EMP commission report, page 34]

The Commission did test the radios and computer systems used by public safety agencies. The radios held up fairly well to fields as high as 50 kV/m. The weak link was the computer systems: "Results indicate that some computer failures can be expected at relatively low EMP field levels of 3 to 6 kilovolts per meter (kV/m)." "[However]... most of the fixed installation public safety radio systems include telecommunication links between the computer-aided dispatch terminals and the main or repeater radio units. Therefore, because of computer failures in dispatch equipment, communication system failures might occur at EMP field levels as low as 3 to 6 kV/m [report page 153]." I believe it's fair to assume that any general purpose unhardened computer that is connected to anything at the moment of an EMP exposure of even low intensity will be probably toast. I'm pessimistic about how well modern Ham gear will hold up, considering much of its technology is identical to that found in general purpose computers.

So far as distance being a protective factor is concerned, I refer the reader to the map on page 6 of the Executive Report. It shows the E1 field strength from an EMP detonation near Chicago falling to 50% intensity only after it was out over the Atlantic beyond Washington, D.C. and New York. Three detonations of that type would cover the entire 48 States with at least a 50% field intensity E1 pulse.