THIS. In the bullshit that is already flooding the market, this is the mindset you should have to deal with reality as best as possible.
Not everything in life is simple decision, like what pizza topping to get. Some decisions, you have to make, and should make, only after a lot of detailed technical thought. There aren’t a ton, but this should be one of them.
Problem is, in the past, these choices were fewer intrinsically, and now are intrinsically exponentially multiplied in this particular dimension, privacy and safety, by everything’s every facet somehow involving networked intelligence and database storage.
I’ll expand it to the Freemarket Outrage Economy, to sum up everything that seems to be happening in truth and in imaginations lately. As in, the world is going around by individual companies contorting all their business model around people thinking the freemarket fixes everything, erroneously, and that whatever pisses people off the most (tabloids, aka Hulk Hogan this week) or the least (people avoiding ChicFilA after the gay comments) is what sells.
Sorry to be off topic, but I don’t even own a tv anymore, and all I hear about is Hogan, Cosby, Clinton, and everyone constantly saying something racist, homophobic, clueless, or outright lying. Everyone is pissed off at everything, big or small. It’s wearing me out badly, and childhood icons have killed enough of themselves lately.
I guess if the the system did any kind of feed-back or active noise canceling it could detect if the antenna was out. On the other hand, it may also be able to tell if the transceiver was out if it is doing careful power management. Either way, I guess you just try it and see what works.
If you are going to target the antenna, i think you probably better closely match the impedance. My first suggestion of just winging it with something in-between 50 ohms and 75 ohms is probably really dumb. If it is a 75 ohm system, you are probably going to push a bunch of current through a 60 ohm resister. You may end up frying the resister or the transceiver.
Perhaps you just measure the existing antenna with a multi-meter and get it’s resistance? Or would that be too easy, and you have to calculate some funky thing that matches the capacitive load of the antenna system at the frequencies you are using? Hmm. Can’t be. If it was, Shaddack would have just suggested switching in a capacitor to eat the signal.
Of course, even when you get the right resistance, I suppose you need something that can dissipate the power that the transceiver is pushing. It probably won’t hurt if you anchor the resister to something that can shed some heat. I expect it’s probably less than a watt.
It would be fun if I could use one of my old 10base2 terminators to match a 50 ohm antenna system. Or an old video RG6 terminator to match a 75 ohm system.
All Rights Reserved. Not available in Maryland. Drink plenty of water. If you try this at home, the Great God Murphy may smite you dead. Or eat a sock. It’s always a toss-up. Remember, only Hugh can prevent florist fryers.
Not really, actually…You won’t have a good impedance match in either case, but you will be close-enough for a low-power system. You can get away with a lot of impedance mismatch, for the cost of loss of signal, but without frying anything, if the transmitter power is sufficiently low in comparison with what its output can withstand.
It is the second. The antenna is a lumped inductive-capacitive load. I am not well-versed with the antenna stuff sufficiently to explain how it works. But with DC load the antenna looks like an open circuit; you’ll find an infinite resistance. (Exception: loop antennas, but these are used at much lower frequencies.)
As I understand it, impedance on a transmission line for RF waves is something like an index of refraction for light. If you get a mismatch somewhere along the line, you get a partial or total reflection of the signal. A matched antenna will radiate all the signal out; a mismatched one (which includes a missing one or a short circuit to ground) will reflect some to all, depending on the degree of mismatch, back into the transmitter output stage. A matched resistor differs from the antenna by dissipating the power as heat instead of radiating it out. The degree of reflection can be measured by instruments as SWR (standing wave ratio).
A good illustration of this effect is TDR, time domain reflectometry, done on cables. There are some youtube videos, I believe. Take a roll of cable, attach to oscilloscope on one end, and send in sharp pulses from a generator. Attach a potentiometer on the other end. On the scope you’ll see the pulse you’re sending in, and echoes from the cable’s end. The magnitude and polarity of the echo will vary with the set resistance of the pot. A demo here:
With cellphone-grade hardware, a one-watt resistor will do the job. With high powers, which at large AM transmitters can reach multiple hundred kilowatts, huge liquid-cooled resistors may be necessary.
The ethernet terminator may work. The instantaneous power is not catastrophical, and the fairly low duty cycle of the transmitter (it transmits in pulses, sending just brief packets of data instead of blasting out full rated power full time) may bring the average power well within the terminator’s rating. Try it while checking its temperature; the worst you can expect is a thin stream of greyish smoke that smells like electrotechnician’s oops.
The trouble with safety is that it’s unpredictable what will go wrong next. There is no way you can programme a machine to predict all catastrophic eventualities. And you can guarantee that the next disaster / accident will be different from the last one. Things go wrong because of unexpected combination of small things not the obvious.
Don’t underestimate stupid humans, especially when there are working in good teams, they are still by far better in thinking out of the box and recognising danger than any machine. Were it not so accidents would be the norm. Life is dangerous business.
Look up Sydney Dekker’s work on cognitive diversity, superadditivity, human error.
Humans are better than machines in edge cases (so far).
However, humans have consistently poor baseline performance in comparison with machines in the standard, simple, common, well-mastered situations.
You can easily end up with a scenario where the gains from the edge cases are way lower than the losses from the common ones.
Except of course from the point of view of the one person (and those for whom he/she was special) who gets knocked off the planet. It’s the old Trolley Problem raising its pretty head.
If it’s UHF/microwaves I’d avoid regular resistors and rather get a proper termination/dummy load. A regular resistor will have too much parasitic inductance/capacitance at those frequencies.
I’ve built some dummy loads 50ohm for amatuer radio. i tested them out with some proper equipment and they behaved pretty poorly above 100Mhz.
Your ability to do this is not exactly improving with time. The old stock is available until it conks out; but such ‘features’ aren’t getting any less common on new units(and even when your ability to use the features is tied to a subscription fee of some sort that doesn’t mean that the system is disabled).
Well, ECUs have already hunted carburetors to the brink of extinction across most of their former range; and anything with an ODB-II interface can be safely assumed to have a CAN bus, possibly several, so I’d go with “Oh, definitely, unless you really like antiques.”
The real question is mostly that of how quickly and thoroughly those computers will receive network connections; the computers themselves are already mostly in place. There has been at least one demonstration of a broadcast attack that exploited head units that improperly handled malicious DAB transmissions; but most of the individualized malice presumably requires one of the cell modem based vehicle connection systems.
Wound resistors are highly unsuitable for high frequencies. They are little coils in disguise. Use either RF-grade resistors, or at least those little SMD chip ones - they are commonly used in gigahertz applications. Example of use here: http://pe2er.nl/wifiswr/
Also, a homemade 50-ohm dummy load that reportedly works at 5,8 GHz with SWR of 1.1, so it is apparently a suitable way.
Until some bureaucrat gets the idea that it should be mandatory. Then it’ll be wirecutters time.
I cannot buy reasonably priced non-specialist electronics using the good old leaded solder anymore. I am stuck with fatigue cracks scheduled to appear at the time of warranty expiration.
Says who? We are not exactly running out of oil; there’s quite a lot in the ground and new is being discovered. It is more difficult to get to than just drill a short hole and let it gush, though.
But there are alternatives. Check out the old Fischer-Tropsch. You can make oil from anything from biomass to coal, and there are still large reservers of coal out there.
Good ol’ Germans used that tech when they needed fuel and were losing access to oil fields when the war was turning bad. South Africa then perfected the tech during the embargo. And now we have new catalysts that are even more selective, for better product choice.
You may not like the pedigree of the tech but it is out there.
I wonder about the EMP hardening of these ones. Is there any way to rig up something similar to that military EMP testbed, but smaller, affordable and for cars? Would something like this half-megavolt rock-disaggregator Marx generator be of use, if fed to a suitable load (e.g. a vircator)?
The issue here is not only hardening for the case of nuclear war, but also for making the vehicle resistant against the HERF devices the police has under development for stopping cars. Modkits hardening cars against them could be a good business.
Yeah, I don’t know about that. My current car is 10 years old, and I had to argue with the sales rep to avoid power steering and power windows. As far as I know, you can’t not get power windows anymore.
Which can be quite a problem if accidentally driving into the ocean. With salt water shorting the circuitry, no way to command the window to go down and flood the vehicle and escape.
And it’d be so easy to have it both ways, just a little mechanics added… A manual fallback is always good to have in reach. Things then tend to fail less brittle.
