Packet Radio on 27Mhz (2011) | Hacker News Reader

Packet Radio on 27Mhz (2011)

youtu.be

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?

Get a technician license. Get a radio. Start playing around. I had one for about 10 years before finally just getting motivated to give APRS a shot. It was just slightly to get my radio actually hooked up to a computer via softmodem and xastir and all that, but it feels good having it together.

Of course, I'm not a huge fan of xastir. At this point, I want to build something new that's not GUI based and see if I can get something that's more useful outside of vnc.

Why stop at a technician license? CW (aka Morse Code) isn't a requirement like it was in my day, so I encourage folks to go all the way to Extra. The question pools are available and the actual material isn't too difficult to master since there are no labs or practical exams. (Plus code is more enjoyable to learn without the added pressure of the tests.)

I wouldn't recommend stopping there, but it's fine for starting. I haven't moved forward since I'm barely using my tech license and have too many hobbies anyway. :)

I'm really pretty interested in learning CW, but haven't been able to dedicate time to it yet. I'm not even quite certain how to pick any up. Most of the time I go looking, I don't hear anything (I've only got 2m/6m/70cm equipment, though).

My radio experience: consumer/ham/Military/University/Industry, both hardware and software. (But currently I deal with databases, 'cause it pays the bills.)

See if a local library has a copy of the ARRL Handbook. There's also a ton of information available on internet. Many hams have blogs, projects, etc available to explore. Sometime back issues of Radio and ham magazines are freely available. http://www.ae5x.com/blog/tag/oldpubs/

There's a large number of kits and other projects that are simple and inexpensive to build. You can spend as much or as little as your budget allows and still have a blast. I've had a nice PSK31 chat with the US East coast from Texas with 3 watts and a simple wire antenna while car camping.

I'm hesitant in telling you to seek out a ham radio club. There's a bitterness among a small percentage of older hams that has discouraged a legion of folks from enjoying the spectrum. But with the internet, you can usually ignore these idiots and find some aspect of radio/electronics and communication with like folks.

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&#...). It's free and there are no ads; just something I did to give back to the community.

I still have an old Tech+ license but I became inactive when I moved away to college and had no rig, no time and no ham friends at ASU. It would be nice to do more with it someday.

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.

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.

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!)

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.

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)

> It's free and there are no ads; just something I did to give back to the community.

This is the spirit that made HAM Radio a success in the first place. I wish more of it would be still present.

Out of the same motivation, I have developed an open source APRS app for Android (http://aprsdroid.org/) written in Scala. It is available (for a fee) on the Market as well, but you can download the APK freely from the home page. :)

aprsdroid is pretty nice. I've used it to test messaging when I'm RF only, and I've gated messages to the internet from my phone using the speaker and an HT. Glad to have it. :)

I didn't know it was written in scala, though. That adds extra awesome to it.

I just got back into ham radio last year. It's more fun than ever. I particularly recommend HF contesting.

What is HF contesting?

this is where people try to make long range contacts via voice or morse code or even digital modes... there are a lot of forms of competing, some consider getting two way communication with each state or country on a continent, or a rare island. some compete with the most number of two way communications in a single session. some try to get contacts with exotic places like remote islands where a radio person has set up a temporary station. there are many forms to this! some try to get the largest distance with the lowest power, etc. i'm not into it myself, but it is a unifying activity and something to do with the airwaves that can be fun.

It's a fun way to make contact with stations all over the world... some of the most technologically advanced stations are owned by contesters. It's really a unique form of sport that pits engineers against engineers (designing optimal antenna systems, station configuration, etc.), with a component of adrenaline and operator skill. It's like a multi year video game with a deeply challenging real world component. Each contest is typically only 48 hours, but it takes years to build a competitive station and the necessary operator skill, understanding of nature (radio wave propagation), etc.

Over the past few years I've done some reading/experimenting with meditation and I've found that high speed CW (morse) contesting puts me in a very relaxed state where I push out everything else from my consciousness. It's really quite awesome, and is lately one of the few things I can do that truly accomplishes this (the other is snowboarding down double black diamond powder).

Get acquainted with the American Radio Relay League or ARRL for short.

http://www.arrl.org/new-to-ham-radio

They provide a wealth of resources. Keep in mind that most larger cities around the world also have ham clubs. Most have regular classes to help you get your license.

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.

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

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

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.

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

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? :)

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.

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