Comment by paulmd | Hacker News Reader

Comment by paulmd | Hacker News Reader

Parent Full thread

In the past that's exactly what they've tried to do, and this usually ends up clobbering the law-abiding users in the process. Most of these bands are pretty close to each other - the 10M HF band is right next to the CB band, the 2M band is right next to the emergency services bands and pretty close to both the aviation bands and the weather radio bands, and so on. Gear from one will pretty much just work on the nearby bands, absent some other protection. You can do filtering, but it's physically pretty hard to make an amplifier work ideally within its band and then immediately stop working when you take it outside its band.

So the FCC's response in the past was to make it illegal to produce anything that could go from [unlicensed power level] up to [licensed power level] on demand. If you wanted to make a 10M amp that could hit say 150W, you had to require at least 75W drive power because that was beyond what a legal CB radio could deliver. Kinda sucked for anyone who couldn't afford a radio with 100W of drive, and I think they eventually let off a bit because they were losing the battle to cheap Chinese junk sold over the internet. They're very proactive about enforcement, they'll get you sooner or later, but until then it's better for everyone if you're not spewing harmonics everywhere.

There are radios and amps that use a frequency analyzer to automatically cut out when operated out of their intended bands, they're just very expensive compared to most of the gear that's out there. And a lot of the Software Defined Radios and so on are actually wideband radios that are physically capable of operating across a bunch of bands. These are very concerning for the FCC, and you pretty much cannot limit these physically, it has to be built into the firmware or the controlling software. Hence the article.

There's also just different rules for different license classes. As a radio amateur, I can also use 2.4 GHz (13cm band) under my license, and I am allowed to operate with up to 1500 to 2500 watts EIRP depending on mode. That is of course subject to lots of limitations including "minimum necessary power", but there's nothing physically stopping you from taking a 13cm amp sold for radio amateurs and running wifi over it. Same frequency, how does the radio know?

> There are radios and amps that use a frequency analyzer to automatically cut out when operated out of their intended bands, they're just very expensive compared to most of the gear that's out there.

Why is that expensive? It obviously can't require fancy hardware if it can also be done in software.

Here's a contrived version of this:

Imagine trying to design a calculator that isn't allowed to display the digit '8' on its LCD display.

In software, the implementation sees if the LCD is being set to a value that contains '8' in binary and if so, ignores the input.

In hardware, you have to have a camera that is pointed at the LCD, and a hardware OCR implementation that looks for the 8, and then a circuit that when the OCR implementation sees an 8, turns off the display.

Just to fill in the context that's missing here:

1. If you have a single radio unit, you can easily do the "software" implementation where you look at what you're going to be broadcasting and cut it off if it's not legal. The problem comes when you have separate radio and amplifiers - the amplifier has no idea what whether you're feeding it 10M or CB frequncies. It will amplify either just fine, so the FCC really prefers you to build in a "hardware" type implementation there (a frequency analyzer that figures out what's going into it). It's just expensive to do so - like if you didn't already have a digital amp, you might easily add 1/4 or 1/2 to the cost just to get some dumb logic built in. And you can still probably get around it if you really try.

2. There is a disproportionate amount of cheap gear and old gear in circulation. We didn't get "smart" rigs until the late 90s at a minimum, and even so they are vastly outnumbered by stuff from the glory days of the 50s, 60s, and 70s. There has always been a relatively small amount of high-power stuff in circulation, and there's even less smart high-power stuff. A lot of the modern kit-built stuff like the Elecraft K2 focuses on QRP (effective operation on low power) instead of crazy high output.

3. This manifests as a CRAZY price curve. It's relatively easy to get an old radio from the 70s that'll do 50 or 100W (especially after factoring in weak, aging tubes, etc). A modern mini-rig that will do 25W or something is also relatively affordable. But if you want something new, powerful, or new AND powerful you can easily jump into the thousands of dollars. For the cost of a modern rig that'll do any given power level, you can afford an older rig and an amp that will put out an equally good signal with substantially more power. Or with a better antenna. And so on.

4. There's nothing wrong with the old gear and things like tubes can be fixed. If you trash your new wünder-rig it's garbage. So given that amateurs are crafty people (the proto-hacker, really) there's a strong incentive to make the old or lower-power stuff work, because it's repairable when it breaks.

Thanks for the info, cbhl and paulmd. I'm afraid I still don't quite get it, probably because I don't understand EE and radio as well as I ought to.

Why is there significant expense in putting a ROM chip between the radio and the amplifier that cuts out certain frequencies? I can see where that's not as simple as mandating software that is simply incapable of generating bad frequencies in the first place, but it intuitively strikes me as the same sort of embedded programming that goes into, say, a microwave oven--I can see it adding some cost, but not so much that it would be unfeasible in e.g. an home wifi router. What am I not understanding?

In hardware, $.15 is "significant expense" because the margins are thin and unit economics.

The list of blocked frequencies changes occasionally (like time zone definitions); if you can't update the "illegal frequency blocking" chip then it becomes illegal to use your otherwise-perfectly-good product once the rules change. Plus, it depends on what country you're in, so ideally if you move (or just go on a vacation) to another countries you don't want to have to throw away your old router/smartphone/smartwatch and buy new ones in the other country.

Chicken and Egg. If you can modify the radio (hardware/software), you can modify the protection device.

Adding a protection device merely shifts the problem (being discussed) from the radio to the protection device.

It achieves exactly nothing.

I'm not sure that follows. On the kind of wifi router that the FCC wants to ban, you can install new firmware because it's designed to allow you to to that. You could have accessible firmware whose signals have to pass through a non-accessible ROM.

You can change the frequency that a thing communicates on by changing the length of the wire in the antenna, and you can change the strength of the signal by changing the shape of the antenna, and the ROM will be none-the-wiser.

An example of the former is "homemade AM radio", where you wrap a lot of wire in a coil, and changing where you complete the the circuit along the coil allows you to "tune into" different frequencies.

An example of the latter is the cantenna, a directional antenna that can be made from a Pringles can.

The sub-ten dollar wideband SDR is a recent phenomenon.

Wideband radios are not all that new. My radio is a Kenwood TS-820S from the 70s and covers multiple bands from 160M to 10M. My cheapo Radio Shack walkie talkie from 15 years ago covers most (all?) of 6M to 2M (i.e. all kinds of serious bands that I'm not allowed to transmit on). My Yaesu VX-5R from 10 years ago can do full-on wideband receive, from 6M up to microwave.

With the help of an auto-tuner to match the SWRs there's no physical reason I can't transmit/receive bands I'm not supposed to. It's not like tweaking a VFO is really a technical challenge, they're well-understood technologies. And the frequency display on my radio is literally just a frequency counter for my own edification, the base TS-820 non-S model doesn't even have one. To find your frequency you look at the dial, there's a printed scale for your band. You know what happens if you are pushing the limit too far? The FCC tracks you down and you get a pink slip telling you that they know what you're up to.

You both underestimate what older radios can do, and overstate what newer radios can do relative to them. The reasons that you didn't see people transmitting off-band before was primarily social, not technological. As for receive, the FCC was flipping out about people intercepting cellphone calls on omniband radios - 15 years ago. Omni SDR was around 10 years ago too, with the same capabilities (see: GNU Radio), it just cost more than $10 for a rig.

I made a short reply as to one reason why I thought that the fancy radios that monitor their own output might be cheaper now or in the not too distant future. I'm grateful for the reply, but I think you've read too much into my little one-line comment.

>Wideband radios are not all that new.

No, but super cheap ones are.

>It's not like tweaking a VFO is really a technical challenge

Well, it's a little bit of a challenge for most (especially non-hams), but sure, there's no magic involved.

>The FCC tracks you down and you get a pink slip telling you that they know what you're up to.

I've heard so many scary stories about the FCC, and yet their enforcement actions page is relatively empty; and hams are always heard complaining about both persistent abusive behavior that the FCC either does little, or is powerless to stop. My impression is that violators, both abusers and unintentional get a lot of chances to correct their behavior; and that FCC enforcement is mostly a paper tiger that can do a bit of damage to someone who wants to comply (for the most part), and can do very little or nothing to stop the worst abusers.

Enforcement actions: https://transition.fcc.gov/eb/AmateurActions/Welcome.html

Warning Letters: http://transition.fcc.gov/eb/AmateurActions/Legacy.html

>You both underestimate what older radios can do, and overstate what newer radios can do relative to them.

I don't think so. I know that these features, or reasonable substitutes for them exist/have existed for some time, but I also know that their widespread use was limited, primarily due to cost. Economies of scale in manufacturing mean that since a TV tuner chip which produced in the billions can be used as an SDR, now there are lots of very inexpensive SDR units available for purchase. For higher end equipment, there is also the fact that DSP tech has advanced at a pretty incredible pace enabling things like the ~$300 dollar 100MHz oscilloscopes in my lab and also the 500MHz scopes in my lab that didn't cost more than our minivan. Sure, many (maybe even most) of the things that can be done with an SDR can also be done with solder and wires, but an SDR can do any/all of them. A super cheap (as in < $10) SDR can act as a frequency analyzer (to use GP's term) can compliment a high quality analog radio design. I suspect that one could add that kind of feature to an analog radio and keep the total additional cost under $10.

>The reasons that you didn't see people transmitting off-band before was primarily social, not technological.

I think you've hit the nail on the head here. There simply isn't any/much of a problem, and where the problems do exist the FCC is largely toothless anyway (and that's arguably a good thing). The FCC sees the potential for cheap consumer equipment that can easily be made non-compliant; they know that they haven't the resources to enforce the rules against millions of people and want to simply prevent it from happening. There is a reason that the FCC has so little enforcement is because nobody who knows them, likes them.

>FCC was flipping out about people intercepting cellphone calls on omniband radios - 15 years ago.

Another reason to dislike the FCC, they made a rule which was almost totally ineffective, and today is completely moot; because the technology prevents the problem that the rule was supposed to prevent. The cost of scanners/radios went up, and some good products were taken off the market and replaced with junk, or simply not replaced. Yay FCC.

> Omni SDR was around 10 years ago too, with the same capabilities (see: GNU Radio), it just cost more than $10 for a rig.

A lot more than $10, and you had less "SD" for your SDR because your PC and the software was simply less capable. Now, a relative noob can start from practically nothing and point and click his/her way to receiving any number of things in an afternoon.

Reply on news.ycombinator.com