

Packet Radio on 27Mhz (2011) - projectmeshnet
http://youtu.be/eFu71XeM998

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tgs
I've had no experience with radio but find this stuff really interesting. You
never know what you'll need to do come the zombie outbreak when the internet
goes down.

Packet radio, HAM, CB... it is all a mystery to me. Is there a beginner's
guide somewhere on getting into this field for cheap?

~~~
unoti
Go get your HAM radio license. It's a great way to get in touch with your
hacker roots, and connect with interesting like-minded people. The most
important resource when any kind of trouble breaks out is friends, and HAM
radio people are great, smart, resourceful people to know.

When you're studying for your license, use my HAM Radio study guide for
Android
([https://market.android.com/details?id=com.tango11.hamstudy&#...](https://market.android.com/details?id=com.tango11.hamstudy&hl=en)).
It's free and there are no ads; just something I did to give back to the
community.

~~~
burgerbrain
Somebody with more experience should correct me here, but I'm under the
impression that the penalties for illegal transmission (for example I believe,
encrypted communications) are harsher for people _with_ HAM licenses.

Something to consider, if that is accurate.

~~~
TheAmazingIdiot
Its usually intentional, malicious transmission the FCC cares about. There was
some lid in Texas that kept on playing laugh tracks and howlers over peoples'
FM communications. In FM, the strongest power transmitter will 'capture' the
receivers in range unlike AM, where you hear a smear of all audio tracks.

The guy was eventually caught. His punishment was $20K and the loss of his
license.

However, in all honesty, an encrypted communication can be claimed that you
are working with digital modes with different compression schemes. The only
real requirement here is to have a call sign in the clear in a common digital
mode (CW preferred). Just dont be stupid and do a dump of a GPG encrypted
block down the xmit.

For example, I regularly run channel 12 on my home wifi gear (european
firmware). On my router, I have a sticker that states my callsign and
EXPERIMENTAL. It's now allowed under part 97 tentatively. I also, out of
respect, went to the 2 local HAM groups and stated what I was doing and where.
If there's interference, I can change it.

~~~
gonzo
I have no idea why you think this is a good idea.

Go look at the ACR specs for the chipset in your AP, and then realize that
they're talking about the 'spacing'(for example) between ch 1 (centered at
2412MHz), 6 (2437MHz) & 11 (2462MHz) in the 2.4GHz band. Note that the center
frequencies are 25MHz apart. In DSSS (1 or 2Mbps) or CCK (5.5 or 11Mbps) your
radio has a signal bandwidth (or frequency occupation) of 22 MHz. Using OFDM
modulation, the signal bandwidth is 20MHz.

Radios do not have an exact edge to their channel, and energy spreads beyond
the edges of the channel boundaries. However, the overall energy level drops
as the signal spreads farther from the center of the channel. The 802.11b
standard defines the required limits for the energy outside the channel
boundaries (+/- 11 MHz), also known as the spectral mask.

At 11 MHz from the center of the channel, the energy must be 30 dB lower than
the maximum signal level, and at 22 MHz away, the energy must be 50 dB below
the maximum level. As you move farther from the center of the channel, the
energy continues to decrease but is still present, providing some interference
on several more channels.

Ch12 is centered at 2467MHz. 11MHz up is 2478MHz. The US ISM band ends at
2485Mhz. In theory you don't need to be a HAM running under part 97 to
transmit here, BUT remember that you're probably transmitting at 100mW
(20dBm), so your radio's design is probably transmitting 50dBm into the edge
of the band.

MOREOVER, the HAM band in-question is 2390-2450 MHz, so you're operating
illegally when you're transmitting WiFi on ch12 (centered at 2467MHz!)

~~~
TheAmazingIdiot
Comments like yours is why I didn't post my callsign.

We've discussed what my proposal was with the 2 local ham groups. One person
works for the FCC and finds non-compliant stations. From what he indicated, as
long as I put "EXPERIMENTAL" on the device, and watch for interference (iow:
be a good amateur operator), I can do this.

I've passed their kind requests, along with publishing what I am doing and
with what wattage I am transmitting. I am also monitoring my emissions as I
usually do when operating.

I'd also like to remind you that an evil device called a microwave oven
transmits more as static on 2.4GHz broadband than my narrowband wifi.

~~~
gonzo
You can think what you like, of course. You're still intentionally generating
OOB emissions. HAMs like you are actually dangerous to the hobby.

A U.S. Federal Standard exists (and is used in most of the world), that limits
the amount of microwaves that can leak from an oven throughout its lifetime to
5 milliwatts of microwave radiation per square centimeter at approximately 5
cm (2 in) from the surface of the oven after sale. (at manufacture, the limit
is 1 mW/cm2 at 5 cm.)

US Dept. of HEW, FDA, Bureau of Radiological Health, “Regulations and
Enforcement of Radiation Control for Health and Safety Act of 1968” paragraph
1030.10; Microwave Ovens pp 36-37 PHEW Publication No. (FDA) 75- 8003, July
1974

Now, what's the EIRP of your setup again? Assuming a 50mW (17dBm) radio and
2.2dBi 'short dipole' antennas, and maybe 1dBm of loss in the connectors/coax,
you're at 18.2dBm EIRP at the surface of the antenna. Call it 65mW for grins.

At 2450MHz, you'll be down -14.2dB 5cm away. 18.2-14.2 = 4dBm, so 2.5dmW @
5cm. You're lower than a worst-case microwave (but higher than anything that's
allowed to be sold!), unless you fit high-gain antennas or high-power radios.

KD5FGA, btw. (also www.netgate.com)

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dlsspy
I've recently got a pretty decent APRS setup on 2 meter. There's a decent
amount of activity around my house. There's a lot of APRS infrastructure, so
things like internet gated messages in and out actually function. It's good to
keep this stuff alive.

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projectmeshnet
You can find more info at <http://reddit.com/r/darknetplan> . Cjdns is
something to look into as well <http://outreach.x10.mx/cjdns.php>

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joshu
Wow. I can actually afford HAM gear now. How does one decide where to start?

~~~
th0ma5
start studying for the exams with online tests, and look for places near you
(often! sometimes in some places multiple times a month) and get a license.
the test teaches you mostly what you can and can't do with your license. you
don't have to buy gear, for instance there are many low parts count projects
you can build using junk components, but read about all the kinds of devices
that people use, and practice soldering. i personally got into radio to use
APRS after seeing hackpgh use it to track weather balloons. since then i build
a very simple direct-conversion software radio, but you can also check out
www.websdr.org to play with those kind of radios online using a java app. best
of luck!! tons of things to explore.

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forgeman
Very cool, thanks for posting the link. I'm sure this will get a few of us
interested in HAM / Packet radio! Thanks again.

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ge0rg
From the discussion here it seems that many hackers do have their amateur
radio license. Maybe somebody with enough karma can set up a poll to find out
how many? :)

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gonzo
Love that the discussion here went to HAM radio, but kinda disappointed that
nobody has pointed out that the video is CB (cheese band), not HAM radio.

