User:Average/Radio Enthusiasts

revolution update v3.2. Much of this is still preliminary and for software radio, be conservative and respectful. Find the note about the FCC and traffic analogy below. Until there's more support of the government, the powers that make radio work are telling me to use the smaller power figures (25W/1mile rather than the 50W) if you are NOT a licensed radio operator. Some new terms are being worked out. Sorry in advance for the confusion and possible brain-dead, wonky usages below. I don't have enough energy to write it up better. Any questions, find Capt. Dynamite.

Just as the FAA allows non-licensed pilots to operate experimental aircraft, there is now some leeway for experimental radio. Find a licensed radio operator for best results, as they can check bands in use and power, etc. You can also encode you callsign on any software you right and earn some cred. The fact is, that RF usage is a lot more chaotic and more confused than a lot of people realize. Manufacturers are often just playing loose with freqencies and power ranges, not even working with the FCC. They simply don't have the expertise. Believe it. You could be the one who helps solidify the field.

For example, some things they don't know yet:

What is the best antennae design? The boundary between your antennae and the radio wave is not completely understood. Digital antennae (variable-length through digital switches at different contact points) is a new arena.
How does differing antennae orientation affect communications?
how does ambient radiation from other radio devices affect reception on other bands? (use a tuned antennae to avoid it)
how best should high-density, multi-way communications, "asynchronous" (without hop limits, packets far from the network may get downloaded days later), be handled? This is new theory to develop, although UUCP protocols and BBSs have dealt with the issue.

Some tools for the arena:

Stray-RF meters for measuring "temperature" of radio environment, these might be helpful in signal modulation
radio spectrum analyzers for showing all bands and power utilization.

Stay free...

Of course, we need inexpensive, public-friendly, two-way, metro-distance for mesh networking and one-way, public-friendly, long-distance communication for broadcasting the revolution.

Ham radio, adhoc/mesh (multi-hop, spontaneous) networking (B.A.T.M.A.N, Byzantium, ZigBee), municipal wifi: these are tools for freedom-lovers everywhere.

Otherwise, it should create little problem to broadcast a low-power, or less than 50Watts²/1-mile-diameter-circle, radio station on some unused, unlicensed frequency (that means 10 devices of 5W each or 1 device at 50W) that conforms to the interval tolerances of the FCC at the given frequency power level (say 0.2% at 1.6GHz) and the tuning accuracy must be tight enough not to wander out of these tolerances. That means on any arbitrary 1-mile circle, your total radiation is <50W, like a heat map that must stay below a certain temperature. Because of the greater work in tuning multiple devices, there should be some loss as you add more devices. So rather than 10 devices at 5W, more like 4.0W. The exact amount of loss here is not yet studied. There is one other restriction: you must be unreceivable at twice your calculated radon (Radon is the area measure correlate to your calculated radiation minimum; e.g., if you've calculated power for 1-mile reception, you must be invisible at 2 miles at that frequency). You won't get protection from the FCC if someone jams your transmission, but hey just invite the jammers over!

So for mesh networking, you have to add up the total number of transmitters and their power in any given mile-circle and keep it under the 50W limit. That means you'll have to re-check total users routinely, perhaps each session (when there's a new IP address/session). This should be acceptible to everyone, including the bureaucrats at the FCC. I base this on citizen radio history, research on existing power usage on various devices, amateur radio, and interactions with the powers-at-large. In any case, don't make the FCC the enemy -- they're trying to solve a constraint problem in a highly aggressive arena with very little input from sources they understand. Licensed radio operators can have lots of leeway if they simply communicate.

If you're using scaled networking with backbones, your power limit needs to stay under the power given by the equations below. Figure out your distance between backbone nodes and calculate your power, then keep your total radiation for all levels below under that value.

Radio transmissions happen in the imaginary, or i, dimension. That is a space of non-reality. Watt² means two such dimensions, i and j. Your antenna catches these imaginary dimensional emissions and your electronics transduces them into your positive dimension as an audio signal. Fractal antennae may worth experimenting with as well as spherical resonant chambers, each tuned (built around) to a desired wavelength.

Put a light on top of your antenna whenever you switch the transmitter on to let the community know when you're making things happen!

In short, for municipal-range radio:

2 mile transmission range limit from unlicensed operators (as measured by single-axis, passive antennae (without gain)) one-way transmission. "Range" here means you shouldn't be able to tune a signal on an passive antenna at said distance.
Any single transmitter can't be over 500W regardless of distance.
Frequency recommendations: CB CH1 can be set aside for datacomm. UPDATE: CH2 may be better, leaving odd numbers for voice and even for future data(?). Old UHF bands are also a good bet (channels 32-34, (477.2000-477.2500MHz) are supposedly set aside. Try those first. Stay away from 2-way radio bands and any emergency bands.
50W²/1mile-diameter-circle total radiation (within specified wavelengths), and less if you don't need it. This is not a suggested power: you must attenuate your transmitter until you get under the range requirement. Different ambient radio environments make different challenges, but the first requirement nails down your limit.
Stay polite: Attenuate radio power from maximum if ambient radio space and device distances allow it. Two people in a coffee shop shouldn't need to be at 25W a piece. Mesh networkers: To this end, also limit continuous broadcast (any beacon node) to a maximum of 1 hour at a time. and no more than 50% duty-cycle for any beacon nodes (15 min beaming your sentinal datapacket, 3/4-hour of radio silence is probably best). (This shouldn't be a problem as you'll be so popular that they'll be plenty of nodes offering service, right?)
Some experimentation may be allowed if you're licensed operator outside the bands given above. Stay off licensed spectra and any bands used for emergencies (medic alert, CB CH9, etc.), and it's always polite to check a band before transmitting (a hand-held HAM radio should suffice). For the sake of the community, consider any unknown transmission as possibly licensed and legit, until deduced or traced otherwise.
If you are a licensed operator, as a courtesy and a possible benefit to yourself, you should place your call-sign in all datalink (and maybe the transport layer to keep your work associated after the datalink layer is stripped off) packets somewhere (it's only 6 bytes).
Probably don't use on commercial aircraft.

If you want to eliminate the range limitation, you can move power down to 1/2 the given limit (25W/mile-radon, 12.5W for two devices), and limit yourself to CB CH1 and UHF 32-34. If you have an antennae solution that allows you to receive at 1000 miles at 25W, you must have some very fine tuners.

It would be very nice if someone made a tabel of how range is affected by frequency. For example in the guideline above you should be able to tune in at 1mi, but not 2mi. Make a table of frequencies and power outputs, to research behavior. In an open area like the Nevada desert would probably be ideal.

Another option for coffee-shop-range radio:

100ft range limit
4.7W² /50ft-diameter-circle max power, again attenuate to satisfy first limit
R/C bands may be best here (which have up to 25W unlicensed watts, btw, far more than this ~5W limit).

Basically, the formula for any given power band for unlicensed 2-way radio, using standard (but tuned to wavelength) antenna is:

Xmitter-Watts²/2*radius < 0.5Watts²/ft-diameter = 0.25W²/ft-diameter each for 2 devices. The unit for the power (W²) is the radule, for the planar area of influence (the foot-diameter), the radon. So the power restrictions or limit restrictions can be calculated based on which number you constrain (numerator or denominator).
max reception distance < 4*radius (radius above)

NOTE: please someone put these terms in a saner format.

If you think about it, 0.5watts²/ft is extremely gentle total radiation limit, yet also tunable. That's 0.25watt²/ft for 2 devices, or an (1/8)W²/ft for 4 devices. This formula allows you to figure out your power no matter how much the distance you want to transmit. Although this document limits transmission to 2 mile, regardless. You'll have to use repeaters, if you want to go beyond this limit, assuming sparse coverage (that your area of influence tapers off logarithmically as you move away from your central users).

Here's the issues to think about with regard to the FCC. Everybody likes to have safe travels when on the roadway, where you are contending with multiple vehicles operating at different speeds in different areas. No one likes the guy zooming by at 100mph in a 55mph zone (akin to someone using more power transmission). We all benefit from ordered traffic, yet we have to lose some of our freedom to have it. That's the idea with government regulations and this is what you should use to argue with the FCC on issues of radio traffic. On an empty road, you might be able to make a case for travelling at 100mph, but not on a busy one or where a lot of people are getting onto the roadway. And in whatever the case there will be occasional randomness -- that's just one of the thing sacrificed for the sake of freedom. They go hand in hand liberty and order. No one can argue with either of these. So just keep it in your mind.

You may not want to set up permanent base stations with your experimental setup.

Exercise #1: You want a 1-way radio station able to broadcast 30 miles.

Feet = x², x is your unknown transmitter power
P = sqrt(5280ft*30mi), re-arranging terms
P must be less than 398 Watts and attenuated until untunable at 60mi on your free-est path. This part is necessary to make the bureaucrats feel safe.

If you want to broadcast in stereo, you'll have halve that amount: half for each channel (L and R) or just under 200W per channel.

Exercise #2: You want a single 2-way conversation around the globe with another licensed radio operator operating at 5000W:

P < sqrt(5280ft*12500mi)
8124 W total energy for unlicensed, global communications,
subtract your conversant's 5000W and you're left with 3124W of MAX power. XXX see note below..

Bonus if you got it that this is also the same you need for 1-way radio since it goes around the earth in both directions. Also the end result of that calculation tells us that 8000W of total power for any mesh networking project for all nodes if you're making a global mesh networking project like Friefunk.

XXX That's a large amount of unlicensed output, you're better off with extreme tuning solutions if you want that distance. So keep the reception limit under 2 miles (and 50W²) until further permission and testing is done.

User:Average/Radio Enthusiasts

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