Connecting to the Internet with Amateur Radio

Yes, a lot of people seem to want to do this. ICOM even claims that you can do it using D*STAR, although they're kinda vague on how it works. There are a few problems with doing so. The most commonly cited one is the "third party rule" (§ 97.115), but this actually isn't a major obstacle in most cases; the real obstacle (in the US, at least) are the list of "prohibited communications" in § 97.113.

The third party rule, as implemented by the FCC, only comes into play on international communications; that is, when one of the two amateur stations in the communication is in the United States (or other area regulated by the FCC) and the other station is not so located. So the third party rule would be a problem if you were in the US and trying to use a radio to communicate with a station in, say, Germany, and then from there to connect to the Internet. However, if both of the stations involved are in the United States, this doesn't come into play. The third party rule says nothing about where the third party in the communication may be located; as far as the radio regs are concerned, it doesn't matter that you're going to a website in Armenia, as long as your radio communication isn't going there.

However, the real problem is that any connection to the Internet would have to be continuously supervised to ensure that no prohibited communications took place over the link. And there are so many things that are prohibited: music; anything encrypted; any message in which the operator has a pecuniary interest other than the occasional sale of radio equipment; obscene or indecent language. Imagine how hard it would be to avoid all of these while browsing the Internet.

On top of that, there's the general prohibition in § 97.113(a)(5) on "[c]ommunications, on a regular basis, which could reasonably be furnished alternatively through other radio services." There are plenty of alternative services that can provide mobile connections to the internet, in most circumstances, at least. There's probably a few edge cases where this won't get in the way (out of the way areas, or during a communications disaster).

The problem that this creates is that the only time that the regulations really allow a ham to connect to the Internet would be during a communications disaster. But because we aren't allowed to do it under ordinary circumstances, there's not a whole lot of incentive to have the equipment and infrastructure in place to do it in the event that we do need it. And once-a-year drills on Field Day aren't really a good test of how the system would perform in an actual emergency. We've become increasingly dependent on the Internet for ordinary and extraordinary communications needs; it's almost certain that in a major disaster getting Internet access active in a disaster zone is going to be a priority, and the FCC, by not letting us do this during non-emergency conditions, makes it that much less likely that we'll be able to when it really does matter.

The other day I came across this old article from 2001 about an effort by hams to provide a backup Internet infrastructure using ham radio services. I don't think they're still around; a search for their organizational name (the Emergency Communications Network) turns up only a company in Florida that seems to be providing telephone-based emergency communication services. (Fat lot of good that'll be during a telecom emergency when the telephone network is down.) I have no idea what happened to them or their idea.

So, the long and the short of it is basically that you really can't use ham radio to connect to the Internet... but we would probably be better off if you could.

Two meter handheld range

Here's another post inspired by a search hit. Some fine soul hit my blog today on a search for "expected range on a 2 meter handheld radio". This search would have brought our feckless reader to this post, which does not fairly answer the question. So, in the hopes that the next person to do this search actually learns something, I'll essay to answer this question.

The answer, of course, is "it varies". The amateur radio two-meter band is a VHF band, and as such is almost entirely line of sight. (Sporadic E skip, tropospheric ducting, meteor scatter, auroral skip, and earth-moon-earth are all quite difficult with an HT, so I won't dwell on them here.) So, basically, the range of any 2-meter radio is going to be limited by the horizon. However, because the atmosphere refracts radio waves considerably more than it does light, the effective radio horizon is about 15% further than visual horizon. So that establishes one of the limits on range: the receiver at the other end must be above the effective horizon. This is a function of four things: the altitude above ground of the transmitter, the altitude above ground of the receiver, the distance between the two, and the terrain between the two. The effective radio horizon for a given location, assuming flat terrain, is about 4.11 kilometers times the square root of the height of the antenna (in meters) above ground. So two stations with their antennas each one meter above ground will be in each others' horizons if they are closer than about 8 kilometers (a typical handheld-to-handheld case). If one of the stations is, instead, a repeater with its antenna 60 meters above ground, the range is nearly 36 kilometers. If one of you is atop the John Hancock Center in Chicago (344 meters), the range would be a whopping 80 kilometers. Of course, all of these are assuming flat terrain; if one of you in on top of a mountain, then that will also increase range, and if there's a mountain between you then you will be out of luck.

This isn't the end of the discussion, though. Not only do you have to have to be within each other's radio horizons, you also have to have enough power to survive path loss. Path loss represents the reduction in strength of the radio wave as it travels through space. Much of this is simply due to the inverse square law: as the wavefront grows in size, it occupies more space without having any more power, and thus has a lower power density. The receiving antenna's size doesn't change, so if it's moved further away it will receive less of the transmitted field. This is "freespace path loss", and if this is all you were facing loss would simply double twice with each doubling in distance (a loss of 6 dB for each doubling in distance, or octave). However, in real situations, other factors also contribute to loss, and in average conditions the effective loss in VHF is closer to 7 dB per octave, with a base at 1 km of about -71 dB. Most HTs will be able to just barely receive a signal at about -120 dBm, and should give suitable performance at about -100 dBm. This means that at 1 km, to have acceptable performance, you'll need to transmit a signal of -29 dBm. That's not even two microwatts. (In practice, you wouldn't get that far on two microwatts, because your HT's antenna probably sucks. More on that below.) Even at the 80 kilometers long-range case above, the path loss is only -115 dB; a signal of 15 dBm, or about 30 milliwatts, would be sufficient. Even with antenna losses, that's possibly within the typical 5 watt (37 dBm) capabilities of your average HT.

However, this discussion ignores one critical factor: the poor antennas that most HTs have. In practice the antenna of a handheld radio has negative gain in most operating environments, and you can expect to lose anywhere from 2 to 5 dB due to this issue alone. Obstacles (other than terrain) can also wreak havoc with the signal; if you're in a car, for example, expect to lose as much as 20 dB due to absorption from the car; other things that can reduce range include trees and buildings. Also, when transmitting within one wavelength of the ground (which for an HT is almost always) a significant portion of the signal is lost into the ground; this can account for up to 10 dB of loss.

However, it remains the case that in almost all cases, radio horizon, and not power, is the primary limitation on VHF range. So, in ordinary conditions, your 2m HT range is going to be about 8 km HT-to-HT simplex and about 25 to 40 km HT-to-repeater (depending mainly on the height of the repeater's antenna).

P.S. All numbers in this article may be wrong. I've tried to get them right but it's late and I may have made mistakes. If you do spot anything wrong, please feel free to hit me.

Too many repeaters

Is there some law that requires ham radio sites to have atrocious web design? Some of the sites I've been at recently (and I won't name names, not right now) have just horrible web design. Blinky graphics, animated horizontal rules, busy background patterns... it's Geocities all over again!

One thing that I've been frustrated by recently is the lack of useful repeater listings for Chicagoland. Most of the listings I can find just list the city or town for the repeater. This is multiply frustrating for me where I am. First, there are just dozens of little suburbs around here, many of which the names of which I forget, and scanning a list of repeaters in Illinois sorted alphabetically for the ones near me is challenging and tedious. Second, a repeater in Chicago may or may not be close enough for me to use; Chicago is a big city and a repeater might not cover the entire city if it's not high enough or is on the wrong side of the Sears Tower or something. Third, many repeaters are listed with a city/town of the residence of the operator or the trustee, not the actual location of the transmitter (which may be miles away and several towns over). K5EHX's repeater list tries to rectify this somewhat, but this database suffers from the fact that most of the repeaters have only a default lat/long of the city center of the listed city (which, as noted, may be incorrect). (Not K5EHX's fault; he can't create data out of thin air anymore than anyone else can.)

I am therefore going through the list of repeaters for my location, trying to update the information as best I can, using the web and emailing operators to the extent possible, and going on air to try to get info when I can't find the info via the web. This is proving to be tedious, but at least it will hopefully help someone.

If you know a repeater that isn't listed in K5EHX, or is incorrect, please add it/fix it as appropriate! Chicagoland isn't the only place where this data needs work.

Toll Avoidance, and Gain Conversions

I occasionally look at my referers to see what people are searching for when they find my blog. There were two in the recent list that stuck out to me: "convert dB to gain" and "chicago route around no tolls". I've obviously touched on these before, or else people wouldn't be finding my blog so easily, but I haven't talked about either directly, so here we go.

Decibels are a dimensionless unit used to relate a measured level against a reference standard. The actual unit is the "bel"; one bel represents a tenfold increase in level as compared to the standard. A decibel is a tenth of a bel, and therefore represents an increase of about 25%, since 10^0.1 is approximately 1.25. To convert decibels to an absolute gain figure, one simply raises ten to the power of the gain ratio expressed in bels. If G is the gain in decibels, then g=10^G/10 is the absolute gain multiplier. The reverse is done with logarithms and is left (for now) as an exercise for the reader.

As for finding a route around Chicago that avoids tolls, this is more complicated. In part, it depends on where you're trying to get and from where. The most common situation where this comes up is when someone is going east to west (or west to east) on I-90 and is routed through Chicago. (I-80 doesn't actually go into Chicago.) Interstate 90 is toll from the Wisconsin state line to just outside Chicago, and then again on the south side of Chicago; avoiding it is not easy. In addition, using the freeway part of I-90 to go through Chicago is not terribly fun; the Dan Ryan is widely regarded as one of the least pleasant freeways on which to drive.

Avoiding the the Skyway toll is easy; just enter Illinois on I-80/94 instead of on I-90. If you're already avoiding tolls you've done this anyway since I-90 in Indiana is the western end of the Indiana Toll Road. Avoiding the Jane Addams toll is much harder as there are no suitable alternative routes for most of its length. (You can avoid the east terminus toll by using I-290.) A lower-toll alternative is I-80 and I-39; you only pay one toll on the portion of I-80 that is overlaid on the Tristate and one on the portion of I-39 that is overlaid on the Jane Addams. You could avoid these by using lesser surface routes, but none of these alternates is very enjoyable. If you're heading far enough west, consider taking I-80 all the way to I-35 (in Iowa) to reconnect with I-90 in Minnesota. If you're coming up from central Indiana, consider using I-74 to I-39 (in Bloomington) or I-80 (in the general area of the Quad Cities). If you are heading up into the Wisconsin coast (Kenosha or Milwaukee), you can try using US 41 instead of I-94 from the north side of Chicago.

Hope this helps someone. If not, oh well.

This post is not about pedophila

I'm very much aware of all the furor, and do not wish to add to it further. It seems, however, that negative public opinion of "one of the most prolific reputation and defamation engines on the internet" is spreading fast:



(Taken from the May 10, 2008 issue of Secret Asian Man by Tak Toyoshima at comics.com; link will only be good for two weeks, sorry.)