Communication if the grid goes down ?

[Tod]

Ham radio can't be jammed? What if the government broadcasts propaganda over all the frequencies the people try to use?

 

[FrancisMarion]

If the grid goes down, the most important people you will need to talk to are those that are your neighbors. So verbal.

but for the intent of the question: I've always liked this scene:

http://www.youtube.com/watch?v=i6LGJ7evrAg

 

[acptulsa]

Ham radio can't be jammed?

Of course it can. Who said otherwise?

 

[Matt Collins]

How many ham radios would it take to relay news from one coast to the other?

If you know what you're doing and have the right equipment, just 1 radio.

 

[Matt Collins]

Ham radio can't be jammed? What if the government broadcasts propaganda over all the frequencies the people try to use?

It would be very very very difficult to do and thus highly improbable. Besides, if you have a modded radio that allows you to transmit outside of ham bands, then you could also likely get around it too.

 

[acptulsa]

It would be very very very difficult to do and thus highly improbable.

Really? You ever try to get a radio signal through on the same frequency as the local clear channel AM station? Try it some time. The government can create one hell of a lot of electromagnetic noise. Bank on it.

Besides, if you have a modded radio that allows you to transmit outside of ham bands, then you could also likely get around it too.

Sure, being flexible in your frequencies is a way to avoid jamming. Of course, there are two issues involved there. If your intended recipient (the person you're trying to communicate with) doesn't know where in the spectrum you're switching to, you wind up talking only to yourself. And once you get outside the bandwidth known as ham radio, the signal's ability to cover great distances is greatly diminished.

 

[VIDEODROME]

Cans and String

 

[Matt Collins]

Really? You ever try to get a radio signal through on the same frequency as the local clear channel AM station? Try it some time. The government can create one hell of a lot of electromagnetic noise. Bank on it.

Not spectrum-wide they can't.

And once you get outside the bandwidth known as ham radio, the signal's ability to cover great distances is greatly diminished.

errr... not exactly.... see this -

http://www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf

 

[acptulsa]

Not spectrum-wide they can't.

Matt, all you need to jam more frequencies in more places is more transmitters. That's all. Excuse me if I don't share your love for underestimating potential enemies.

errr... not exactly.... see this -

http://www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf

Okay. Now tell me what in God's name that has to do with which frequencies carry farther in which medium, or conform to the curvature of the earth better. I dare you.

 

[liberty2897]

If data throughput is not an issue, you could do a number of things with a digital stream to improve a link and protect from interference and many other problems with wireless links.

Something along these lines

Ultra narrow band-width channel
Receiver with excellent noise figure (first LNA with very low noise figure and high gain)
Brick wall band pass filter after the IF
Simple QPSK modulation
A combination of block-code forward error correction wrapped around a convolutional correction code with a low coding rate
Frequency hopping with hundreds of channels hopping in a pseudo-random sequence just fast enough for a small, complete packet to fit in a single channel.
Maybe dynamic preamble and frame sync words based on the current channel and position in the hopping sequence (protection from synchronized jamming)

I think a system like this would go a long way to protect simple low-rate messaging systems.

[edit]
If you decided not to abide by the regulations, there are even more things you could do... obviously.

 

[TheTexan]

Matt, all you need to jam more frequencies in more places is more transmitters. That's all.

More transmitters, and more men to guard those transmitters.

 

[UtahApocalypse]

Google HSMM MESH. Its ham radio internet. We gave streamed full pbx voip systems, video, web server, email.... Etc.

 

[liberty2897]

More transmitters, and more men to guard those transmitters.

All those transmitters would need a LOT of power too! Probably have to have several coal plants everywhere to block everything...

 

[jdcole]

It depends on your communications needs. Are you trying to communicate a block over? The next county? The other side of the world?

Ham radio is your best bet - with the right equipment and some learning on your part you can send text & data over ham. Aside from ham, though, you do have some options for a more localized effort - FRS/GMRS radios, CB radio, and Marine radio are all options to look into.

Some good resources:
American Preppers Network Radio Net - The "communications arm" of the American Preppers Network. Some good information, more prep-oriented than your regular Ham enthusiast site.

Amateur Radio Relay League - Founded in 1914, the American Radio Relay League is the national association for amateur radio in the USA. Today, with more than 158,000 members, ARRL is the largest organization of radio amateurs in the United States. Lots of good technical information.

General information on Packet Radio (being able to pass digital data packets over analog radio): http://en.wikipedia.org/wiki/Packet_radio Also has links to other packet technologies, like D-STAR. BBS systems, e-mail, text chat, small file transfers, and more can be done over ham.

For more localized communications, FRS/GMRS radios and CB radio is a safe bet. CB is fine in the car or as a base station, and there are some fine handheld units. Other than that, Garmin actually makes a GPS/2-way radio (FRS/GMRS), digital camera/NOAA weather alert radio combination, their Rino 655t. The topo 100k maps are esily replaced with the (much better) topo 26k maps. If you have multiple Garmin Rino's, you can see each other on your map, making keeping track of friends/family easy. They have lower models, as well. I work as a Satellite technician in Afghanistan right now, and we use the Garmin Rino 110's for the digital compass and exact LAT/LONG when putting up dishes.

If you're concerned about batteries, get the Midland XT511. It combines a 2-way radio (FRS/GMRS), AM/FM radio, NOAA weather radio, flashlight, and USB charge port in a portable package. Comes with rechargeable batteries, and can be recharged via built-in hand crank dynamo. 90 second of cranking provides roughly one hour of continuous-use power.

 

[jdcole]

Oh, and as for jamming radio communications? The military has got you on that one - they have a fleet of jammers that have been used in OIF and OEF to effectively neuter radio-controlled IED's, and they are perfectly good at knocking out all legitimate comms as well. It's a common problem over here in Afghanistan - the Army with leave their Dukes (a type of jammer) on when they drive into the FOB and knock out all comms not in it's exclude list -mostly military frequencies.

Here's a system that the USMC uses: http://www.marcorsyscom.usmc.mil/sites/cins/USMC CREW/USMC CREW 2.0/CHAMELEON.html
Here's a great series of articles about IED's, and the Jammers the military is using against them. Note the things they can jam (key fobs, cell phone, frs radio, etc.): http://www.barthworks.com/military/ied02.htm

 

[Matt Collins]

Oh, and as for jamming radio communications? The military has got you on that one - they have a fleet of jammers that have been used in OIF and OEF to effectively neuter radio-controlled IED's, and they are perfectly good at knocking out all legitimate comms as well. It's a common problem over here in Afghanistan - the Army with leave their Dukes (a type of jammer) on when they drive into the FOB and knock out all comms not in it's exclude list -mostly military frequencies.

Here's a system that the USMC uses: http://www.marcorsyscom.usmc.mil/sites/cins/USMC CREW/USMC CREW 2.0/CHAMELEON.html
Here's a great series of articles about IED's, and the Jammers the military is using against them. Note the things they can jam (key fobs, cell phone, frs radio, etc.): http://www.barthworks.com/military/ied02.htm

That's very localized and on a specific set of frequencies. They cannot jam the entire spectrum all at once in all places.

 

[Matt Collins]

Matt, all you need to jam more frequencies in more places is more transmitters.

See my previous post.

Okay. Now tell me what in God's name that has to do with which frequencies carry farther in which medium, or conform to the curvature of the earth better. I dare you.

Because some bands do that better than others given specific conditions.

All those transmitters would need a LOT of power too! Probably have to have several coal plants everywhere to block everything...

Exactly, it's not really feasible.

 

[Matt Collins]

Google HSMM MESH. Its ham radio internet. We gave streamed full pbx voip systems, video, web server, email.... Etc.

What about this? http://en.wikipedia.org/wiki/IRLP

 

[jdcole]

Matt - I can tell you from personal experience that if they want to drop the comms out in a 1km radius, they can. And they can do it even further than that when they crank the power. And yes, if they want to block out a spectrum (HF, VHF, UHF, etc.) they can. All of it. Goodbye HAM, cell phones, FRS/GMRS, Wifi/Wimax, CB, AM/FM. Incredibly easy to do.

Like I said, I'm a satcom engineer here in Afghanistan - I also manage the data network (including around 30-35 wireless shots) and manage the VHF radios we use (mostly motorola GP360's) and yes, the Army can drop our comms easily. The Marines at least remember to turn off their Dukes/Chameleons/THOR/etc. before they come back on the base.

 

[Carson]

Torch light?