Suggestions for Hardware/driver WIFI combo that allows low level signal access

[Geoffrey S. Mendelson]

On 7/2/2013 9:13 PM, Micha Feigin wrote:

>
> I'm currently working in the states, probably should check Israeli/USA
> law at some point. What I have now is this interesting setup which
> implements narrow bandwidth radar at the 2.4GHz range. As far as I know
> it is legal in the states (it uses readily available hardware as well)
>
> http://www.glcharvat.com/Dr._Gregory_L._Charvat_Projects/Cantenna_Radar.html


Dr. Charvat has an amateur radio license, callsign N8ZRY.

As for the 2.4 gHz band being available for unlicensed use for 
unapproved devices I have no idea. I do know that it is NOT legal in 
Israel.

There was a conflict between the IDF and Wifi and Bluetooth devices and 
the IDF was given a huge sum of money to buy new equipment to get off 
the short range bluetooth channels, and channels 4-8 of WIFI.

Then Omri Sharon came back from vacation and showed his father some 
WIFI/Bluetooth device and by order of the Prime Minister, all Bluetooth 
and the EU Wifi channels were allowed. (1-12).

However the power limit of 100 mW EIRP was strictly enforced and amateur 
radio operators lost their ability to use higher power.

5.8 gHz was allowed here April 1, 2012.

Still one would have to be careful what you do, placing a USB WIFI 
dongle or a gain antenna of any sort inside a coffee can would raise the 
power beyond the 100mW EIRP limit.

The famous Pringles can antenna is illegal both in the US and Israel. So 
are all of those $20 Yagi antennas on eBay, although if there is 
sufficient feed line loss they would be legal in the US.

I think the best thing to do would be to contact Charvat directly and 
ask him for advice about what you can and cannot do.

If you require an Amateur radio license, you can study for a technican 
class license in the US in a weekend (there often are "cram" classes) 
and take the test almost anywhere. If you are at MIT, I'm sure there is 
a radio club and people to help you.

If I were you while you were at it, I would go at least as far as a 
General class license, the next step up. If you are an Israeli citizen, 
you can then get an Israeli license without taking any tests, as long as 
you can prove that you were studying in the US at the time.

The MOC is legally required to accept your US license for conversion 
even if you flew in for the weekend, took the test and flew home, but it 
is a lot easier if you are living there when you take the test.

Getting the equivalent of a General or Extra Class license in Israel is 
far more difficult than it is in the US.


>
>
> It basically connects a signal generator to a voltage controlled
> ocsilator with 200MHz bandwidth around 2.4GHz.
> I was looking to expand on this idea in the direction of the work by
> Dina Katabi from MIT CSAIL which require hacking the signal that the
> radar sends
>
> http://people.csail.mit.edu/fadel/wivi/
>
> The trick is not to change spectrum or intensity, but play a bit with
> the signal modulation within the regulated frequency range. Most of the
> stuff could probably also be done within the legal / standard WIFI type
> communication, but I need finer control over timing / encoding which
> would probably be either very hard or impossible to achieve going
> through the regular network stack.
>

That's very interesting. She uses standard WIFI hardware, channels and 
data streams which would make it legal.

More likely, what you will have to do to use WIFI hardware is not only 
control the timing, but to figure out what bit patterns produce the 
signals that you want.

Note that the legality of WIFI equipment and signals are based upon the 
transmitter, in the US it is legal to do almost anything with the receiver.

You may want to look at the USB DVB-T dongles that are being used as 
software defined radios. I don't know of any that work as high as 
2.4gHz, but there may be one by now.



> I am also looking at UWB / XBAND but that is a completely different
> discussion that involves people that are allowed to do it and very
> custom (expensive) hardware.

Way beyond this discussion.

Geoff.


-- 
Geoffrey S. Mendelson,  N3OWJ/4X1GM/KBUH7245/KBUW5379