Consultants say interference in vehicle electronics is possible
in [Technical]
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From: Scott Dorsey on 26 Mar 2010 13:19 dbu'' <nospam(a)nobama.com.invalid> wrote: >Go here to read about the FCC rules which might apply to the situation >you mentioned. I don't believe there is such a rule regarding "three >orders of magnitude" > ><http://www.access.gpo.gov/nara/cfr/waisidx_09/47cfr15_09.html> > >Check back when you find it and cite the paragraph so that I can learn >too. Nope, that's just part 15 which really just applies to unlicensed radiators that aren't covered under any other service. The old "Class D Citizens Band" is licensed under Part 95 subpart D. Take a look at section 95.410, and 95.411. If you need more information, take a look at Part 95 subart E regarding the power rules. The friendly people at the FCC say four watts carrier power on AM, or 12 watts PeP on SSB. This means multi-kilowatt linears are not legal. This means using modified 10M ham radio equipment on the CB band is not legal (also due to the type acceptance requirements). Oh yes, "freebanders" transmitting on the broadcast auxiliary frequencies and in the amateur radio band with modified high power CBs are also illegal. Now, there was a time many years ago when the FCC was actually operated by engineers, and they had people who would come to your home or your vehicle and take your radio equipment away and leave you with a very large fine for illegal operation. However, we now live in an era when the FCC is run by lawyers who are more interested in using radio services as a profit center and they don't actually have many people who have the skills required for enforcement. But this does NOT mean it is legal. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis."
From: Scott Dorsey on 26 Mar 2010 13:23 AJL <8239(a)fakeaddress.com> wrote: >Hams (amateur radio operators) can legally run 1500 watts in the US. >And many do so using homebrew mobile installations. At this power >level if the installation is not done correctly the car electronics >can not only malfunction but be damaged. Absolutely. And presumably hams have the skill required to make sure that they are doing this properly and safely. K4UMI used to have a 1KW CW rig in his pickup truck which he called his "electronic brake" because it substantially slowed the vehicle when he put the key down. >But RF can be unpredictable and cause problems at low power also. I >have had my cruise control affected with as little as 5 watts when >using a VHF or UHF frequency (144, 220 or 440 MHz). Rerouting of >cables and/or better grounding usually fixed it. It's perfectly predictable.... and some car manufacturers will tell you specifically what to do and what shielding and leakage current issues will exist. It's not always easy to predict for the end user who may not know where every ground connection in the vehicle is, but the car manufacturers have RF guys who have that information. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis."
From: clare on 26 Mar 2010 15:45 On 25 Mar 2010 21:06:13 -0400, kludge(a)panix.com (Scott Dorsey) wrote: >In article <4babdcf1$1_2(a)news.tm.net.my>, TE Cheah <4ws(a)gmail.com> wrote: >>15 yr ago I read of 1 car in USA using auto cruise control drtve >>past a truck using CB radio, this car @ once got unintended >>acceleration, this driver switched off his auto cruise & ended this >>problem. He told medias to warn users of auto cruise control >>against CB radios. > >It's not just cruise control... there are a huge number of trucks out on >the road that are violating the FCC emission regulations by three orders >of magnitude. Consequently anything that isn't very carefully shielded >with proper grounding design can have serious problems. >--scott Over 100 watts of output from the linear amps on a LOT of highway rigs.
From: clare on 26 Mar 2010 15:51 On Thu, 25 Mar 2010 21:52:28 -0400, dr_jeff <utz(a)msu.edu> wrote: >clare(a)snyder.on.ca wrote: >> On Thu, 25 Mar 2010 17:28:15 -0500, dbu'' <nospam(a)nobama.com.invalid> >> wrote: >> >>> In article <4babdcf1$1_2(a)news.tm.net.my>, "TE Cheah" <4ws(a)gmail.com> >>> wrote: >>> >>>> 15 yr ago I read of 1 car in USA using auto cruise control drtve >>>> past a truck using CB radio, this car @ once got unintended >>>> acceleration, this driver switched off his auto cruise & ended this >>>> problem. He told medias to warn users of auto cruise control >>>> against CB radios. >>> Maybe fifteen years ago, but EMI suppression has advanced since then in >>> the automotive industry and many other industries too. >> There was ONE model of cruise control I heard about that was >> extra-fussy about CB Radio interference and IIRC it was OK with a 4 >> watt unit installed in the vehicle, but a 100 watt Linear amp in a >> vehicle within a couple hundred feet could "jam" it. >> >> Those cruise control units were VERY primitive compared to anything on >> the market today. The affected unit was made by ARA if I remember >> correctly and the problem only occurred if using the engine speed >> sensor option instead of the magnets on the driveshaft - and that was >> closer to 20 or 25 years ago (very early 1980s - early Chevy Citation >> comes to mind. > >Cruise control usually used vehicle speed rather than engine speed. If >the car kicks in a lower gear (e.g., when going up hill), then the car >would slow down to keep the engine speed constant. > >I am not saying that there weren't any cars that used engine speed >rather than vehicle speed, but I would think that there are few. > >Jeff I've installed likely hundreds of aftermarket cruise controls - and on front drive vehicles - and particularly with automatic transmissions, there were a LOT that used engine RPM to sense speed.. Compucruise had that option for sure, as did ARA if I remember correctly, and at least one other major manufacturer that I cannot remember right now.. If the transmission downshifted the cruise control immediately shut down, the same as on a standard shift car. ANYTHING that allowed the engine speed to climb quickly disengages the cruise on these units - without requiring a clutch switch if installed on a standard. I do remember at least one GM X-Car installation that didn't like a HAM radio installation - and another - can't remember what right off hand - that didn't like the old mobile telephone system installation.
From: clare on 26 Mar 2010 16:07
On Thu, 25 Mar 2010 22:27:52 -0400, dr_jeff <utz(a)msu.edu> wrote: >Obveeus wrote: >> "Scott Dorsey" <kludge(a)panix.com> wrote in message >> news:hoh1a5$jpd$1(a)panix2.panix.com... >>> In article <4babdcf1$1_2(a)news.tm.net.my>, TE Cheah <4ws(a)gmail.com> wrote: >>>> 15 yr ago I read of 1 car in USA using auto cruise control drtve >>>> past a truck using CB radio, this car @ once got unintended >>>> acceleration, this driver switched off his auto cruise & ended this >>>> problem. He told medias to warn users of auto cruise control >>>> against CB radios. >>> It's not just cruise control... there are a huge number of trucks out on >>> the road that are violating the FCC emission regulations by three orders >>> of magnitude. Consequently anything that isn't very carefully shielded >>> with proper grounding design can have serious problems. >> >> But if this was the real issue it would be much more easily detected and >> repeatable. > >Wow! People are using CB radios with 12,000 W of power. That would >require a 1000 AMP alternator just for the radio (12 V x 1000 A = 12,000 >W). Note: the FCC limit is 12 W and 3 orders of magnitude is 1000 (10 x >10 x 10). > >Jeff Not necessarily - you don't know what the amplitude of the transmission is. It might not be 12 volts..Also the efficiency of the transmitter. The output of an Icom 2200 is 65 watts. It runs on 13.8 volts and draws 15 amps during transmit and .8 on standby - so 14.2 amps at 13.8 volts - or 196 watts for about 30% efficiency...... |