Acoustic Modem - use your mobile radio to log in to your buddy's lap top secure

Originally posted by ignorant_ape
reply to post by Rocketman7

 

will not work - as the radio handset you link to does not allow duplex traffic

Two radios, on different channels at the same time is your duplex traffic. You need 4 radios, two acoustic couplers for two people.

The Yaesu system I was referring to is the HRI-100 Wires-II Interface kit which can be connected to any DTMF equipped radio with an external mic input. It uses the Wires-II internet linking protocol and acts as a modem between radio and computer. I'm not very familiar with the system and you would have to research whether or not it could be made to work for your situation.

Also you may want to look into the AeroComm AC4790 series transceiver modules if you are tech savy enough. I've used these for many projects and they are amazing. They are tiny (about 2in x 2in x 0.2in) but are rated for up to 20 miles, unlicensed without an amplifier. They are packed with built in features that are made for two way digital packet communication over a network that the modules can manage themselves, even in a cluster without a master. They have built in DES encryption, they are a spread spectrum, burst mode device which makes them more difficult to track down and very difficult for even professional organizations to eavesdrop on.

The units only cost around $40 and up depending on power rating. Be aware though that they require a simple support circuit for power, line level matching, and function control. There is a development kit you can get that comes with two ready made computer interfaces if you want to go that way but I usually have to build my own control circuits due to size constraints. Here is a control circuit I designed for one recently. Its designed to put the module to sleep in order to save batteries, wake it up occasionally to listen for a command code, wake up an on board GPS and transmit GPS coordinates, to the command station, etc.


It is for this wildlife tracking collar prototype, The transceiver modules are very small. the whole tracking collar weighs only 65grams even though it has enough batteries to last for years, a GPS and its own on command mechanical release mechanism.


Here it is on an 8 pound fawn.


I think these are going to be about as good as it gets for an inexpensive, off the shelf solution for short ranges and you could look into amplifier modules for longer range as well.

You may also want to check out This Wikipedia article which explains amateur packet radio techniques.

Originally posted by dainoyfb
You may also want to check out This Wikipedia article which explains amateur packet radio techniques.

Thanks. I have been chatting about this in another thread. I found out that Ham radio can't receive APCO-25 which means I wouldn't know about any emergency in my area as it happened.

They have all gone on to a new system. Its digital now.

I am starting a new thread on an APCO-25 device I found that kicks ass. The Home Patrol One..

Just wanted to say I meet a lot of communication folks in my industry and one of my customers and I were chatting about the internet (his was down at the moment) and he was telling me about the days before the internet had fully emerged that he used a radio system to link his computer/modem to a friend and that they had experimented a lot with the system just for fun and although it was slow they still could share data or communicate in a way that was not boring. Sorry I can't remember more of the specifics or offer more info other than I know he used his TV antenna on the roof and low voltage. Seems very interesting...

Originally posted by FiberLight
Just wanted to say I meet a lot of communication folks in my industry and one of my customers and I were chatting about the internet (his was down at the moment) and he was telling me about the days before the internet had fully emerged that he used a radio system to link his computer/modem to a friend and that they had experimented a lot with the system just for fun and although it was slow they still could share data or communicate in a way that was not boring. Sorry I can't remember more of the specifics or offer more info other than I know he used his TV antenna on the roof and low voltage. Seems very interesting...

Well someone I spoke to today, lives on a boat, and he told me about D-STAR and Icom radios and how they use repeaters for digital communications so the signal is clear. Which is great as long as the Internet is up and as long as the repeater is up. And you can text, and send 3 web cam images at a time.

The baud rate was 900 now improved to 4800 bps which is pathetic compared to my do it yourself in the field setup at 26000 bps with the acoustic couplers. But its slick and allows that captain to use the Internet out at sea. He was here in ATS.

All this is nothing though compared to that bridge which does high speed wi fi that you could stream hi res video with for 40 km. For 99 bucks. For 99 bucks, you could be big brother for your city, just make em all tune in.
Or Else!


Chocolate rations are up 50 percent today I know because I just had a king dong.

The radio solution is inefficient, and in all likelihood would not work without massive modification of multiple radios themselves. One also has to consider that these radios are designed with human speech in mind and do not have the fidelity to handle the analog carrier with a low enough noise ratio. One would end up with a communication of all error correction and no actual real data.

The OS has nothing to do the ability to "redirect ports" and have a modem "blind dial" (ignore dial tone). Blind dialing is achieved with the initialization string sent with the number to be dialed to the modem when attempting a connection. Setting up com ports can be done with any OS.

The easiest solution is to use the wifi you already have. It is very easy to set up a "ad hoc" network to go peer to peer between two or more computers with no router or access point involved.

You can also buy USB wifi adapters that will broadcast in the 1 and 2 watt range. Alfa makes a few of them.
In fact I have two if them. The AWUS036H is a 1 watt 802.11 b/g adapter, the AWUS036NH is a 2 watt 802.11b/g/n adapter. You can even get them in kits with a 9 db antenna included with the normal 5 db antenna that normally comes with them. They normally run under $40.00.

Using this solution would provide you with decent speeds, full encryption and the ability to set up with anybody, not just people with a bunch of radios wired into their computers.

I think the specs for the bridge is 30km, but that is based on the propagation delay optimization for maximum bandwidth. With a good enough antenna almost any line of sight distance would be achievable. I've seen experiments where 100km was achieved with only 100mw on a standard Linksys WRT54. They had to have one end of the experiment up on a mountain to get past the curve of the earth at that distance.

Keep in mind that the 30 kms is only going to be achieved with a directional antenna. Good if you are trying to keep a low profile though.

There are several rural Internet providers in my area that put bridges on old satellite dishes (18 or 24 inch), point them along the ground, and manage hi speed links from their towers to farms over 40km away.

The amount of sheer idiocy in this thread makes my head hurt. The only person who has a clue what he is talking about is dainoyfb.

I agree with Dreamwatcher. You will never get 26000bps through a radio that only has a 8khz audio bandpass.

reply to post by Rocketman7


well, were talking complete civilization collapse right?

in such a situation, wind power would probably be the best source of energy available to the survivors, which because of its height would be a perfect place to mount a dish, aimed toward the next network node or something.

maybe an omnidirectional antenna mounted to the pole with a bright red lamp or something, so distant users could orient their dish toward it.

anyway, say you used a 5 watt antenna, with a router and a lamp, it couldnt consume more than 50 watts, conservatively. which could be powered by a relatively modest wind turbine.

Originally posted by Dreamwatcher

The radio solution is inefficient, and in all likelihood would not work without massive modification of multiple radios themselves. One also has to consider that these radios are designed with human speech in mind and do not have the fidelity to handle the analog carrier with a low enough noise ratio. One would end up with a communication of all error correction and no actual real data.

The OS has nothing to do the ability to "redirect ports" and have a modem "blind dial" (ignore dial tone). Blind dialing is achieved with the initialization string sent with the number to be dialed to the modem when attempting a connection. Setting up com ports can be done with any OS.

The easiest solution is to use the wifi you already have. It is very easy to set up a "ad hoc" network to go peer to peer between two or more computers with no router or access point involved.

You can also buy USB wifi adapters that will broadcast in the 1 and 2 watt range. Alfa makes a few of them.
In fact I have two if them. The AWUS036H is a 1 watt 802.11 b/g adapter, the AWUS036NH is a 2 watt 802.11b/g/n adapter. You can even get them in kits with a 9 db antenna included with the normal 5 db antenna that normally comes with them. They normally run under $40.00.

Using this solution would provide you with decent speeds, full encryption and the ability to set up with anybody, not just people with a bunch of radios wired into their computers.

Yeah but what about distance? Coverage? Lets suppose I want to set up a WAN on the cheap. Like 99 bucks.

There is a mountain here above this city (Victoria BC) called the Malahat. So the distance to the mountain is let me see 10 or 12 miles from downtown to the peak.

And there is a road that leads up the mountain. A highway so getting there is no problem.

And it overlooks Georgia Strait looking at Mount Baker, man it might hit Texas with a real good antenna and lots of juice. So you could set up a real good base station up there and get some good range. You would hit Port Angeles and Seattle with ham radio easy. Victoria you could cover with a good bridge. I would think. It says it can transmit 40 km high speed connection.

You could hit Port Angeles, and Victoria. I think, let me check the map...

It might just reach Port Angeles.

And that bridge apparently can be had for 99 bucks. But you need an external antenna for it and I have to see what is the best antenna for that.

Then 10 solar panels, 4 truck batteries, battery converter charge manager, a lap top, run windows server, and Bob's yer uncle. Log on to the wireless network, from Victoria and maybe all the way to Port Angeles.

So then if TSHTF you can set up a large area network in no time that way. The only problem is it is line of sight. So in Victoria and Port Angeles they need to put their wireless receiver in a window facing the mountain.

And it probably won't work if the view is obstructed I don't know. Its a cheap solution but it probably won't go through buildings.

Originally posted by snarfbot
reply to post by Rocketman7

 

well, were talking complete civilization collapse right?

in such a situation, wind power would probably be the best source of energy available to the survivors, which because of its height would be a perfect place to mount a dish, aimed toward the next network node or something.

maybe an omnidirectional antenna mounted to the pole with a bright red lamp or something, so distant users could orient their dish toward it.

anyway, say you used a 5 watt antenna, with a router and a lamp, it couldnt consume more than 50 watts, conservatively. which could be powered by a relatively modest wind turbine.

Wind might work. Maybe both solar panel and wind turbine. I am not sure about the light though because if people know its there they might go see what it is and then mess with it.

I think it would be unattended. Log in remote to manage the server, keep it open to all guest log in mostly, at least to start and then develop it and link to mount Baker, then from there to the next mountain arranging the network via ham radio I guess. You know get volunteers or something and maybe within a week you might have some sort of coverage. Depending on how many survivors there are and how savvy they are.

From Mount Baker you could hit Mt. Rainier and cover Washington state or most of it.
But then you would need more than one parabolic dish antenna at 35dBi and you would probably need AC power.

Let me see...

100 Watts

So the big problem with those is the power. Generating 100 watts of power is no easy thing to do without fuel and someone there.
Its only as much as a light bulb but just running a lap top takes 10 solar panels and 4 truck batteries.

Originally posted by dainoyfb
I agree with Dreamwatcher. You will never get 26000bps through a radio that only has a 8khz audio bandpass.

I don't know. It depends on the acoustic coupler. It converts analog to digital and all it does is take the peaks. Maybe its all relative.
Maybe it just filters everything out but the peaks. It uses error correction protocols. It wouldn't be that important locally because the bridge would work fine. But if you had to connect long range with a ham radio, then you can get some range that way. you are not going to get it with a parabolic dish because of power consumption.

You are not going to be able to use D-Star if the net is down or the repeater is down and the repeater needs a generator to run.

Whats the power consumption of the FT-817ND let me check...

"With five Watts and even simple, portable vertical antennas, it should be possible to work over 100 countries within a few weeks in the Spring and Fall contest seasons. Every effort must be made, of course, to devise and use effective antennas, but five watts is only 13 dB down from 100 Watts. How many stations running 100 Watts have you worked that were S9? A five-Watt signal would be only very slightly less than S7, for comparison purposes!"
here buit you need two for each and a coupler for each

You see packet radio is not something many people know anything about. It is not easy to do.

But connecting two radios to a coupler anyone could do.

OK I found a modem. Kantronics. 245 bucks 1200 bps.

and they have a 9600 for 500 bucks. Well, thats something I suppose. I am not sure I want to spend a grand for two modems, or 1400 for two ft-817NDs either.

245 bucks though might be a worth while investment but 1200 bps? I remember 1200 bps. You could access a BBS with 1200 bps but downloading a file took forever and as soon a s bird landed on the phone line anywhere between you and it, you lost your signal.

It would probably work though. If other people had them. Its no good if you are the only one who has one.

And now with D-Star there may be no reason for people to want one.

Yeah that rocks that Kantronics for 245 even at 1200 bps you can communicate across the world.The range of your radio. The best part? Runs a long time on a 9volt battery.

With this one for 750 bucks all you are doing is connecting the mic and speaker so it is the same principal as the acoustic coupler.

It works for them, it will work for 74 bucks with the acoustic coupler modem.

I am sure it would. Now as for getting 26,000 bps well maybe that acoustic coupler is just a darn good product, It is the fastest acoustic coupler made.

Well. I feel exonerated now. In fact I feel, victorious.

Originally posted by Dreamwatcher
The OS has nothing to do the ability to "redirect ports" and have a modem "blind dial" (ignore dial tone). Blind dialing is achieved with the initialization string sent with the number to be dialed to the modem when attempting a connection. Setting up com ports can be done with any OS.

Lets suppose Apollo 14 would not be coming home unless you could get two cheap GMRS radios scabbed onto a lap top - one on the mic and one on the speaker, to communicate with a mirror setup at Houston.

Are you trying to tell me, that we would have to tell their wives and children that they would not be coming home for Christmas?

Cause it can't, be, done???

Of course it can be done. We just don't know how to do it. Its the same thing that is going on inside the acoustic modem. You just convert an analog signal to digital.

The reason the acoustic coupler has a rating of 26,000 is because anything over that probably has too many errors since its difficult to pick the data out of an analog signal. Like a voice signal.

But if you have good reception on your radio, you will get high baud rates with the coupler.

If you were a computer genius you could do it without the coupler. But for 74 bucks I am just going to buy another coupler.

If a guy wanted to make himself a little business, he could package a couple cheap radios with a line in and a mic in and some software and sell it in computer stores or online. Maybe.

I am sure its not that difficult to do if a person knows his electronics. Its a matter of getting the sampling rate

But then you are not allowed to use digital communications on the family band so its only useful when law and order has broken down, and you are in the apocalypse I guess.

The way I see it, a couple acoustic couplers, and 4 radios will allow two people to exchange files, pictures, and so on, across the distance of your radio reception, provided you get a clear signal.

And that could mean, someone goes somewhere close to the action, to do recon and then sends pictures to the home base.

Or, you send the women and children to an island where they will be safe, and if they need some file you can send it to their lap top. As long as they have a couple radios and an acoustic coupler, you can just send files back and forth. Short duration com link via radio and acoustic coupler.

Worth the money I think to have that option.

If those women and children are talking on the radio?

I want mine sending text messages encoded and encrypted instead thank you.

You know what else you better do?
Record your voice saying "ok I am ready to connect as soon as I finish cleaning my guns"

Have them play that recording with the third radio when you want to connect your two computers to chat.

Want a Christmas present to keep your family comms safe during the apocalypse?

ok. Take a photo of some trees. Cut a 100x100 pixel area and save that as a bmp stamp. Put one stamp on lap top a and one stamp on lap top b.

Every byte you send with lap top a add the pixel value as you go across line by line then start again at the top.

On lap top b, every byte you receive subtract the pixel value as you go across line by line one pixel at a time of the stamp copy. Unbreakable, only those two computers can decode the data. Not in a bajillion years could anyone else ever decode that data. And wi fi can be hacked by a teenage punk with a thumbnail drive in 5 seconds with a couple utilities had on the net, but its almost impossible to hack a simple telephone com chat program and impossible to intercept that message. 35 years of computing taught me a couple things at least.

Thats your wife and daughter there on that island hiding. So when they log onto your computer in the city, they don't use a password. Passwords can be cracked. That computer first sends that stamp. If that stamp matches, ok, you are logged in. If that stamp doesn't match, you are disconnected.

The same goes if you want to access your remote pc on a mountain that is running the server. Although who cares about it.

Your family is more important.

So that computer sends the stamp, the stamp matches, you are logged in, now every byte is encoded with that stamp. If, your daughter uses 10,000 exclamation marks in one post, they might get the stamp.
(10,000 repeated characters will mirror the stamp) so if you are extremely paranoid, scramble the stamp first with a small math algorithm so it no longer looks like trees and then even if they see the stamp, it will look like random noise. You know, x3 div 2 the stamp and save it using a utility you made.

Yes this requires some basic programming skills but you could do it in visual basic even.
Or Delphi which would be probably best for this.

You can download a free com program with source, a simple one, add that and presto! You are super safe.

If someone records the transmission and plays it back it will connect won't it?

So you have to be a little more paranoid than that. You have to have a number system as well. Like date and time.

So that the stamp is modified by date and time every time it is used. However then you have to synchronize your watches so you better have a different system.

Some simple system like every time you connect to each other the com program increments by one. Or you use your birthday, then their birthday, yours then theirs, you will maybe never beat the Pentagon or the code crackers at Princeton, but you will fool most bad guys who might be in the field. And thats really all you need.