krw@att.bizzzzzzzzzzzz wrote:> On Mon, 18 Oct 2010 11:24:11 -0700, Joerg <invalid@invalid.invalid> wrote: > >> krw@att.bizzzzzzzzzzzz wrote: >>> On Sun, 17 Oct 2010 17:14:42 -0700, Joerg <invalid@invalid.invalid> wrote: >>> >>>> krw@att.bizzzzzzzzzzzz wrote: >>>>> On Sat, 16 Oct 2010 12:57:04 -0700, Joerg <invalid@invalid.invalid> wrote: >>>>> >>>>>> krw@att.bizzzzzzzzzzzz wrote: >>>>>>> On Sat, 16 Oct 2010 08:14:50 -0700, Joerg <invalid@invalid.invalid> wrote: >>>>>>> >>>>>>>> Andrew Smallshaw wrote: >>>>>>>>> On 2010-10-11, Tim Wescott <tim@seemywebsite.com> wrote: >>>>>>>>>> Are there any wireless sub-systems that are just "fall off a log" easy >>>>>>>>>> to integrate into an embedded system? >>>>>>>>>> >>>>>>>>>> The ideal gizmo would go into an OEM product, wouldn't require the OEM >>>>>>>>>> to mess with any certification issues, would make the product appear as >>>>>>>>>> a serial device to a host computer via BlueTooth, would talk to it's >>>>>>>>>> local embedded processor via serial, and would be plug and play. >>>>>>>>>> >>>>>>>>>> The higher the data rate the better, up to about 100kbps or so. >>>>>>>>>> >>>>>>>>>> Any such things out there? Any that you have personal mileage with and >>>>>>>>>> like or particularly dislike? I'm being lazy and haven't even looked at >>>>>>>>>> ads or done any web searches. >>>>>>>>> Have a look at http://www.quasaruk.co.uk/acatalog/ALPHA_TRX_Module.html >>>>>>>>> >>>>>>>>> I haven't used those modules myself. I've used some of their AM >>>>>>>>> stuff in the past (albeit for experimentation rather than in anger) >>>>>>>>> but that is only good for 2400 baud. This is good for 115200, SPI >>>>>>>>> interface and $7.35 per unit from Digi-key. No Bluetooth though. >>>>>>>>> >>>>>>>> You mean this one? >>>>>>>> >>>>>>>> http://www.rfsolutions.co.uk/acatalog/DS-ALPHA-TRX-5.pdf >>>>>>>> >>>>>>>> Couldn't find the words FCC or "pre-certified" in there, so be careful. >>>>>>>> Also, I found that any schemes that aren't frequency-agile are not all >>>>>>>> that reliable. Especially with rather vulnerable AM protocols. >>>>>>> Just curious... What's the worry about certification? Certifying an >>>>>>> intentional radiator costs a little, but not all that much more than >>>>>>> certifying an unintentional radiator (containing a certified module). If our >>>>>>> lab's interpretation of the (FCC) regs is correct, the intentional radiator >>>>>>> covers a *lot* of the sins of the rest of the box. BTW, we don't do this, but >>>>>>> it is an interesting kink in the regs. >>>>>>> >>>>>> The FCC has made the process fairly friendly lately but last time the >>>>>> cost was another $5k, AFAIR. Plus you must use a TCB certified lab which >>>>>> may mean a longer drive, and possibly higher fees for the regular EMC >>>>>> job. Some companies just ship the stuff, without one of their engineer >>>>>> witnessing the testing (I strongly discourage clients from doing that). >>>>> It costs us about $2K (maybe a little less) to have the scans run for >>>>> unintentional radiation, assuming it passes the first shot. ... >>>> Well, but that's in Jaw-jah, not Taxafornia :-) >>> Same companies. The unintentional scans (line and radiated) take about four >>> hours, which translates to $1600 in the 10m chamber (*much* more reliable than >>> a slightly less expensive 3m chamber). >>> >> But then all the high ones need to be worked of out in the range, mostly >> using a receiver. Which adds hours. That's why the winter rule is BYOJ >> (bring your own jacket) :-) > > I don't follow. >Way this works: You go into the chamber where there is a computerized setup that logs the whole chebang, conducted radiated horizontal/vertical. Out comes a list and then usually there are some close calls. If one or more were way above limits then you pack up and come back after some redesign. If none were above or just vy a smidgen everything gets trundled out to the open space setup. There's a hut with a big fat receiver in there and (hopefully) some hot coffee. The DUT gets placed on a rotary table outside. Now they take the list of close calls and check all those again. This is because chamber measurements are not very precise.>>>>> ... We had a nasty >>>>> experience were it took many attempts and several weeks. $5K would have been >>>>> a bargain. That disaster was at least half the fault of the testing lab, >>>>> though, so we try to not go there anymore. >>>>> >>>> That's why I urge clients to send an experienced engineer along _and_ do >>>> pre-compliance checks inhouse. >>> In our case, these were useless. With our equipment I can't even get a decent >>> sniff. >>> >> Mostly I just use a computer-controlled scanner. If there is a nasty >> emission somewhere it'll find it. Sure, I can't quantify it here in the >> lab but after a couple of decades on the beat you know what'll cause >> problems, just like an older cop can look a guy in the eyes and tell >> that "he dunnit". > > Scanner? Does it cover the entire range (30mHz to a few GHz)? >Not 30 millihertz :-) Goes from close to DC to a little above 3GHz.>>>>> It is silly to just ship stuff off to the lab. If anything goes wrong (it >>>>> always does) there is no one there to fix it. I'm the one who generally goes. >>>>> I kinda like Atlanta. ;-) >>>>> >>>>>> If you build thousands of units a year it certainly makes sense. Of >>>>>> course, you also have to factor in and amortize your own design work on >>>>>> the RF portions of the project that would otherwise already have been >>>>>> handled by the module vendor. That often gets overlooked. >>>>> I'm not talking about designing the RF section, rather only the certification >>>>> part. specifically, whether to use the RF module's certification and then >>>>> certify your box as an unintentional radiator or certifying the entire box as >>>>> an intentional radiator. >>>> For small qty stuff (meaning not millions/year) it's almost always >>>> better to use the module's cert and slap that extra sticker from its mfg >>>> onto the client's box. Only one more sticker, next to all the other >>>> mandatory ones like "Do not put in mouth" and all that :-) >>> But the module's cert doesn't certify the whole box, unless there isn't >>> anything else in the box. >> >> For the intentional part it usually does, the mfg would tell you that >> (and supply the cert/sticker). Unless you do some unauthorized mods. The >> unintentional part needs to be tested just like it is with non-RF gear. > > Understood, but my point is that the intentional limits are considerably > higher than the unintentional, outside some forbidden zones, so it's far > easier to pass. Actually, they're so lax that you'd have to *try* to fail > them. ;-) >It doesn't matter, you still have to pass regular (unintentional) EMC outside your intentional transmit band. That part doesn't get any easier. But why pay the extra chunk of money for field strength measurements on the ISM band or wherever you are transmitting, when you don't have to? That's like paying sales tax for the same item in two states.>> If the mfg waffles on the stickers and cert copies, run. > > That's not my point.Ok. Then why not just slap on the sticker, do only the regular EMC and be done with it? Of course the EMC lab needs to know about the intentional radiator part so they don't flag that. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Wireless that's "Fall off a log" easy?
Started by ●October 11, 2010
Reply by ●October 18, 20102010-10-18
Reply by ●October 19, 20102010-10-19
On Mon, 18 Oct 2010 18:53:20 -0700, Joerg <invalid@invalid.invalid> wrote:>krw@att.bizzzzzzzzzzzz wrote: >> On Mon, 18 Oct 2010 11:24:11 -0700, Joerg <invalid@invalid.invalid> wrote: >> >>> krw@att.bizzzzzzzzzzzz wrote: >>>> On Sun, 17 Oct 2010 17:14:42 -0700, Joerg <invalid@invalid.invalid> wrote: >>>> >>>>> krw@att.bizzzzzzzzzzzz wrote: >>>>>> On Sat, 16 Oct 2010 12:57:04 -0700, Joerg <invalid@invalid.invalid> wrote: >>>>>> >>>>>>> krw@att.bizzzzzzzzzzzz wrote: >>>>>>>> On Sat, 16 Oct 2010 08:14:50 -0700, Joerg <invalid@invalid.invalid> wrote: >>>>>>>> >>>>>>>>> Andrew Smallshaw wrote: >>>>>>>>>> On 2010-10-11, Tim Wescott <tim@seemywebsite.com> wrote: >>>>>>>>>>> Are there any wireless sub-systems that are just "fall off a log" easy >>>>>>>>>>> to integrate into an embedded system? >>>>>>>>>>> >>>>>>>>>>> The ideal gizmo would go into an OEM product, wouldn't require the OEM >>>>>>>>>>> to mess with any certification issues, would make the product appear as >>>>>>>>>>> a serial device to a host computer via BlueTooth, would talk to it's >>>>>>>>>>> local embedded processor via serial, and would be plug and play. >>>>>>>>>>> >>>>>>>>>>> The higher the data rate the better, up to about 100kbps or so. >>>>>>>>>>> >>>>>>>>>>> Any such things out there? Any that you have personal mileage with and >>>>>>>>>>> like or particularly dislike? I'm being lazy and haven't even looked at >>>>>>>>>>> ads or done any web searches. >>>>>>>>>> Have a look at http://www.quasaruk.co.uk/acatalog/ALPHA_TRX_Module.html >>>>>>>>>> >>>>>>>>>> I haven't used those modules myself. I've used some of their AM >>>>>>>>>> stuff in the past (albeit for experimentation rather than in anger) >>>>>>>>>> but that is only good for 2400 baud. This is good for 115200, SPI >>>>>>>>>> interface and $7.35 per unit from Digi-key. No Bluetooth though. >>>>>>>>>> >>>>>>>>> You mean this one? >>>>>>>>> >>>>>>>>> http://www.rfsolutions.co.uk/acatalog/DS-ALPHA-TRX-5.pdf >>>>>>>>> >>>>>>>>> Couldn't find the words FCC or "pre-certified" in there, so be careful. >>>>>>>>> Also, I found that any schemes that aren't frequency-agile are not all >>>>>>>>> that reliable. Especially with rather vulnerable AM protocols. >>>>>>>> Just curious... What's the worry about certification? Certifying an >>>>>>>> intentional radiator costs a little, but not all that much more than >>>>>>>> certifying an unintentional radiator (containing a certified module). If our >>>>>>>> lab's interpretation of the (FCC) regs is correct, the intentional radiator >>>>>>>> covers a *lot* of the sins of the rest of the box. BTW, we don't do this, but >>>>>>>> it is an interesting kink in the regs. >>>>>>>> >>>>>>> The FCC has made the process fairly friendly lately but last time the >>>>>>> cost was another $5k, AFAIR. Plus you must use a TCB certified lab which >>>>>>> may mean a longer drive, and possibly higher fees for the regular EMC >>>>>>> job. Some companies just ship the stuff, without one of their engineer >>>>>>> witnessing the testing (I strongly discourage clients from doing that). >>>>>> It costs us about $2K (maybe a little less) to have the scans run for >>>>>> unintentional radiation, assuming it passes the first shot. ... >>>>> Well, but that's in Jaw-jah, not Taxafornia :-) >>>> Same companies. The unintentional scans (line and radiated) take about four >>>> hours, which translates to $1600 in the 10m chamber (*much* more reliable than >>>> a slightly less expensive 3m chamber). >>>> >>> But then all the high ones need to be worked of out in the range, mostly >>> using a receiver. Which adds hours. That's why the winter rule is BYOJ >>> (bring your own jacket) :-) >> >> I don't follow. >> > >Way this works: You go into the chamber where there is a computerized >setup that logs the whole chebang, conducted radiated >horizontal/vertical. Out comes a list and then usually there are some >close calls.Ok...>If one or more were way above limits then you pack up and >come back after some redesign.BTDT.>If none were above or just vy a smidgen >everything gets trundled out to the open space setup. There's a hut with >a big fat receiver in there and (hopefully) some hot coffee. The DUT >gets placed on a rotary table outside. Now they take the list of close >calls and check all those again. > >This is because chamber measurements are not very precise.Hmm. The chamber is the gold standard. A 3M isn't worth much, but we've had no trouble with the 10M. The rotary table and all that jazz is in there.>>>>>> ... We had a nasty >>>>>> experience were it took many attempts and several weeks. $5K would have been >>>>>> a bargain. That disaster was at least half the fault of the testing lab, >>>>>> though, so we try to not go there anymore. >>>>>> >>>>> That's why I urge clients to send an experienced engineer along _and_ do >>>>> pre-compliance checks inhouse. >>>> In our case, these were useless. With our equipment I can't even get a decent >>>> sniff. >>>> >>> Mostly I just use a computer-controlled scanner. If there is a nasty >>> emission somewhere it'll find it. Sure, I can't quantify it here in the >>> lab but after a couple of decades on the beat you know what'll cause >>> problems, just like an older cop can look a guy in the eyes and tell >>> that "he dunnit". >> >> Scanner? Does it cover the entire range (30mHz to a few GHz)? >> > >Not 30 millihertz :-)No? ;-)>Goes from close to DC to a little above 3GHz.What sort?>>>>>> It is silly to just ship stuff off to the lab. If anything goes wrong (it >>>>>> always does) there is no one there to fix it. I'm the one who generally goes. >>>>>> I kinda like Atlanta. ;-) >>>>>> >>>>>>> If you build thousands of units a year it certainly makes sense. Of >>>>>>> course, you also have to factor in and amortize your own design work on >>>>>>> the RF portions of the project that would otherwise already have been >>>>>>> handled by the module vendor. That often gets overlooked. >>>>>> I'm not talking about designing the RF section, rather only the certification >>>>>> part. specifically, whether to use the RF module's certification and then >>>>>> certify your box as an unintentional radiator or certifying the entire box as >>>>>> an intentional radiator. >>>>> For small qty stuff (meaning not millions/year) it's almost always >>>>> better to use the module's cert and slap that extra sticker from its mfg >>>>> onto the client's box. Only one more sticker, next to all the other >>>>> mandatory ones like "Do not put in mouth" and all that :-) >>>> But the module's cert doesn't certify the whole box, unless there isn't >>>> anything else in the box. >>> >>> For the intentional part it usually does, the mfg would tell you that >>> (and supply the cert/sticker). Unless you do some unauthorized mods. The >>> unintentional part needs to be tested just like it is with non-RF gear. >> >> Understood, but my point is that the intentional limits are considerably >> higher than the unintentional, outside some forbidden zones, so it's far >> easier to pass. Actually, they're so lax that you'd have to *try* to fail >> them. ;-) >> > >It doesn't matter, you still have to pass regular (unintentional) EMC >outside your intentional transmit band. That part doesn't get any >easier. But why pay the extra chunk of money for field strength >measurements on the ISM band or wherever you are transmitting, when you >don't have to? That's like paying sales tax for the same item in two states.If you read the regs, at least for FHSS radiators in the ISM bands, anything outside the band, and outside one or two do-not-collect-$200 bands, must only be 20dB down from the in-band radiation. Easy-peasy, when you're radiating a hundred or two milliwatts.>>> If the mfg waffles on the stickers and cert copies, run. >> >> That's not my point. > > >Ok. Then why not just slap on the sticker, do only the regular EMC and >be done with it? Of course the EMC lab needs to know about the >intentional radiator part so they don't flag that.Because the intentional limits are almost impossible to fail. We pass easily, now, so there isn't any point in gaming the system, but the rules leave the door wide open.
Reply by ●October 19, 20102010-10-19
On Mon, 18 Oct 2010 18:29:04 -0500, "krw@att.bizzzzzzzzzzzz" <krw@att.bizzzzzzzzzzzz> wrote:>>Mostly I just use a computer-controlled scanner. If there is a nasty >>emission somewhere it'll find it. Sure, I can't quantify it here in the >>lab but after a couple of decades on the beat you know what'll cause >>problems, just like an older cop can look a guy in the eyes and tell >>that "he dunnit". > >Scanner? Does it cover the entire range (30mHz to a few GHz)?BTW, what kind of antennas are you using at 30 milli Hertz ? Even if 30 MHz .. multiple GHz is intended, getting a sufficient antenna bandwidth is a challenge. At 30 MHz the wavelength is 10 m, so doing the measurement in the far field requires a big room.
Reply by ●October 19, 20102010-10-19
On Tue, 19 Oct 2010 07:20:50 +0300, Paul Keinanen <keinanen@sci.fi> wrote:>On Mon, 18 Oct 2010 18:29:04 -0500, "krw@att.bizzzzzzzzzzzz" ><krw@att.bizzzzzzzzzzzz> wrote: > >>>Mostly I just use a computer-controlled scanner. If there is a nasty >>>emission somewhere it'll find it. Sure, I can't quantify it here in the >>>lab but after a couple of decades on the beat you know what'll cause >>>problems, just like an older cop can look a guy in the eyes and tell >>>that "he dunnit". >> >>Scanner? Does it cover the entire range (30mHz to a few GHz)? > >BTW, what kind of antennas are you using at 30 milli Hertz ?Big ones.>Even if 30 MHz .. multiple GHz is intended, getting a sufficient >antenna bandwidth is a challenge.That's the least of the problems.>At 30 MHz the wavelength is 10 m, so doing the measurement in the far >field requires a big room.Or far out in the field.
Reply by ●October 19, 20102010-10-19
"krw@att.bizzzzzzzzzzzz" wrote:> > On Tue, 19 Oct 2010 07:20:50 +0300, Paul Keinanen <keinanen@sci.fi> wrote: > > >On Mon, 18 Oct 2010 18:29:04 -0500, "krw@att.bizzzzzzzzzzzz" > ><krw@att.bizzzzzzzzzzzz> wrote: > > > >>>Mostly I just use a computer-controlled scanner. If there is a nasty > >>>emission somewhere it'll find it. Sure, I can't quantify it here in the > >>>lab but after a couple of decades on the beat you know what'll cause > >>>problems, just like an older cop can look a guy in the eyes and tell > >>>that "he dunnit". > >> > >>Scanner? Does it cover the entire range (30mHz to a few GHz)? > > > >BTW, what kind of antennas are you using at 30 milli Hertz ? > > Big ones. > > >Even if 30 MHz .. multiple GHz is intended, getting a sufficient > >antenna bandwidth is a challenge. > > That's the least of the problems. > > >At 30 MHz the wavelength is 10 m, so doing the measurement in the far > >field requires a big room. > > Or far out in the field.Like the outdoor antenna range we used at the original CE plant in Cincinatti. -- Politicians should only get paid if the budget is balanced, and there is enough left over to pay them.
Reply by ●October 19, 20102010-10-19
On Tue, 19 Oct 2010 02:29:40 -0400, "Michael A. Terrell" <mike.terrell@earthlink.net> wrote:> >"krw@att.bizzzzzzzzzzzz" wrote: >> >> On Tue, 19 Oct 2010 07:20:50 +0300, Paul Keinanen <keinanen@sci.fi> wrote: >> >> >On Mon, 18 Oct 2010 18:29:04 -0500, "krw@att.bizzzzzzzzzzzz" >> ><krw@att.bizzzzzzzzzzzz> wrote: >> > >> >>>Mostly I just use a computer-controlled scanner. If there is a nasty >> >>>emission somewhere it'll find it. Sure, I can't quantify it here in the >> >>>lab but after a couple of decades on the beat you know what'll cause >> >>>problems, just like an older cop can look a guy in the eyes and tell >> >>>that "he dunnit". >> >> >> >>Scanner? Does it cover the entire range (30mHz to a few GHz)? >> > >> >BTW, what kind of antennas are you using at 30 milli Hertz ? >> >> Big ones. >> >> >Even if 30 MHz .. multiple GHz is intended, getting a sufficient >> >antenna bandwidth is a challenge. >> >> That's the least of the problems. >> >> >At 30 MHz the wavelength is 10 m, so doing the measurement in the far >> >field requires a big room. >> >> Or far out in the field. > > > Like the outdoor antenna range we used at the original CE plant in >Cincinatti.I hope you did your measurements in the middle of the night and compensated for any space and local system noises :-).
Reply by ●October 19, 20102010-10-19
Paul Keinanen wrote:> > On Tue, 19 Oct 2010 02:29:40 -0400, "Michael A. Terrell" > <mike.terrell@earthlink.net> wrote: > > > > >"krw@att.bizzzzzzzzzzzz" wrote: > >> > >> On Tue, 19 Oct 2010 07:20:50 +0300, Paul Keinanen <keinanen@sci.fi> wrote: > >> > >> >On Mon, 18 Oct 2010 18:29:04 -0500, "krw@att.bizzzzzzzzzzzz" > >> ><krw@att.bizzzzzzzzzzzz> wrote: > >> > > >> >>>Mostly I just use a computer-controlled scanner. If there is a nasty > >> >>>emission somewhere it'll find it. Sure, I can't quantify it here in the > >> >>>lab but after a couple of decades on the beat you know what'll cause > >> >>>problems, just like an older cop can look a guy in the eyes and tell > >> >>>that "he dunnit". > >> >> > >> >>Scanner? Does it cover the entire range (30mHz to a few GHz)? > >> > > >> >BTW, what kind of antennas are you using at 30 milli Hertz ? > >> > >> Big ones. > >> > >> >Even if 30 MHz .. multiple GHz is intended, getting a sufficient > >> >antenna bandwidth is a challenge. > >> > >> That's the least of the problems. > >> > >> >At 30 MHz the wavelength is 10 m, so doing the measurement in the far > >> >field requires a big room. > >> > >> Or far out in the field. > > > > > > Like the outdoor antenna range we used at the original CE plant in > >Cincinatti. > > I hope you did your measurements in the middle of the night and > compensated for any space and local system noises :-).I didn't work on the anenna test range. It was on the flat roof of the factory, and quite hot except in the dead of winter. There was a tiny fiberglass shed for the unlucky to cool off between tests, but it was well over 100 degrees most of the time. The only time I went up there was one night to see what a nasty job it was. That was around 8 PM, and it still took your breath. -- Politicians should only get paid if the budget is balanced, and there is enough left over to pay them.
Reply by ●October 19, 20102010-10-19
krw@att.bizzzzzzzzzzzz wrote:> On Mon, 18 Oct 2010 18:53:20 -0700, Joerg <invalid@invalid.invalid> wrote: > >> krw@att.bizzzzzzzzzzzz wrote: >>> On Mon, 18 Oct 2010 11:24:11 -0700, Joerg <invalid@invalid.invalid> wrote: >>> >>>> krw@att.bizzzzzzzzzzzz wrote: >>>>> On Sun, 17 Oct 2010 17:14:42 -0700, Joerg <invalid@invalid.invalid> wrote: >>>>> >>>>>> krw@att.bizzzzzzzzzzzz wrote:[...]>> If one or more were way above limits then you pack up and >> come back after some redesign. > > BTDT. >Me, too :-( But those weren't wasn't my designs ...>> If none were above or just vy a smidgen >> everything gets trundled out to the open space setup. There's a hut with >> a big fat receiver in there and (hopefully) some hot coffee. The DUT >> gets placed on a rotary table outside. Now they take the list of close >> calls and check all those again. >> >> This is because chamber measurements are not very precise. > > Hmm. The chamber is the gold standard. A 3M isn't worth much, but we've had > no trouble with the 10M. The rotary table and all that jazz is in there. >That would be up to the EMC lab I guess. If they sign on the dotted line without open range measurements, well, dicey. The labs I went to never did that unless all the nasties were way under the limits.>>>>>>> ... We had a nasty >>>>>>> experience were it took many attempts and several weeks. $5K would have been >>>>>>> a bargain. That disaster was at least half the fault of the testing lab, >>>>>>> though, so we try to not go there anymore. >>>>>>> >>>>>> That's why I urge clients to send an experienced engineer along _and_ do >>>>>> pre-compliance checks inhouse. >>>>> In our case, these were useless. With our equipment I can't even get a decent >>>>> sniff. >>>>> >>>> Mostly I just use a computer-controlled scanner. If there is a nasty >>>> emission somewhere it'll find it. Sure, I can't quantify it here in the >>>> lab but after a couple of decades on the beat you know what'll cause >>>> problems, just like an older cop can look a guy in the eyes and tell >>>> that "he dunnit". >>> Scanner? Does it cover the entire range (30mHz to a few GHz)? >>> >> Not 30 millihertz :-) > > No? ;-) > >> Goes from close to DC to a little above 3GHz. > > What sort? >Mine is the Icom R-1500. Has a mini console for quick checks when I don't want to fire up the PC. If you go PC-only then there's the similar PCR-1500 for about $100 less. Nice thing is, you can listen to stuff in SSB, on every frequency. This is valuable beyond belief if you must knock a few dB off stuff that's already in the noise. With an analyzer that has only a display and maybe some rather crude AM detector with headphones your eyes will hurt at night, especially for guy like me who need a different set of glasses between 0603/0402 soldering and looking at screens. Civilian class A/B are easy. Aircraft category M, different thing. I can crank up the big stereo speakers here and don't even have to don headphones. Of course, this means I can't listen to Bluegrass while doing EMC work. But the Shepherd doesn't like these funny gargles and warbles, leaving her pillow and walking out of the room, giving me "the look". She likes Bluegrass :-)>>>>>>> It is silly to just ship stuff off to the lab. If anything goes wrong (it >>>>>>> always does) there is no one there to fix it. I'm the one who generally goes. >>>>>>> I kinda like Atlanta. ;-) >>>>>>> >>>>>>>> If you build thousands of units a year it certainly makes sense. Of >>>>>>>> course, you also have to factor in and amortize your own design work on >>>>>>>> the RF portions of the project that would otherwise already have been >>>>>>>> handled by the module vendor. That often gets overlooked. >>>>>>> I'm not talking about designing the RF section, rather only the certification >>>>>>> part. specifically, whether to use the RF module's certification and then >>>>>>> certify your box as an unintentional radiator or certifying the entire box as >>>>>>> an intentional radiator. >>>>>> For small qty stuff (meaning not millions/year) it's almost always >>>>>> better to use the module's cert and slap that extra sticker from its mfg >>>>>> onto the client's box. Only one more sticker, next to all the other >>>>>> mandatory ones like "Do not put in mouth" and all that :-) >>>>> But the module's cert doesn't certify the whole box, unless there isn't >>>>> anything else in the box. >>>> For the intentional part it usually does, the mfg would tell you that >>>> (and supply the cert/sticker). Unless you do some unauthorized mods. The >>>> unintentional part needs to be tested just like it is with non-RF gear. >>> Understood, but my point is that the intentional limits are considerably >>> higher than the unintentional, outside some forbidden zones, so it's far >>> easier to pass. Actually, they're so lax that you'd have to *try* to fail >>> them. ;-) >>> >> It doesn't matter, you still have to pass regular (unintentional) EMC >> outside your intentional transmit band. That part doesn't get any >> easier. But why pay the extra chunk of money for field strength >> measurements on the ISM band or wherever you are transmitting, when you >> don't have to? That's like paying sales tax for the same item in two states. > > If you read the regs, at least for FHSS radiators in the ISM bands, anything > outside the band, and outside one or two do-not-collect-$200 bands, must only > be 20dB down from the in-band radiation. Easy-peasy, when you're radiating a > hundred or two milliwatts. >Huh? So you can be way above class B limits in, say, the aircraft bands? Do you have a link there? If you also know anything like that in the tax code I think lots of people would be all ears :-)>>>> If the mfg waffles on the stickers and cert copies, run. >>> That's not my point. >> >> Ok. Then why not just slap on the sticker, do only the regular EMC and >> be done with it? Of course the EMC lab needs to know about the >> intentional radiator part so they don't flag that. > > Because the intentional limits are almost impossible to fail. We pass easily, > now, so there isn't any point in gaming the system, but the rules leave the > door wide open.Sure, when you are a good designer or use pre-cooked modules they are easy. But why spend that extra money to test if it's already done? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Reply by ●October 19, 20102010-10-19
Paul Keinanen wrote:> On Mon, 18 Oct 2010 18:29:04 -0500, "krw@att.bizzzzzzzzzzzz" > <krw@att.bizzzzzzzzzzzz> wrote: > >>> Mostly I just use a computer-controlled scanner. If there is a nasty >>> emission somewhere it'll find it. Sure, I can't quantify it here in the >>> lab but after a couple of decades on the beat you know what'll cause >>> problems, just like an older cop can look a guy in the eyes and tell >>> that "he dunnit". >> Scanner? Does it cover the entire range (30mHz to a few GHz)? > > BTW, what kind of antennas are you using at 30 milli Hertz ? >Up in your neck of the woods you just rent a high voltage power link from Vattenfall and have them give the insulators a nice spit-shine before :-) [...] -- SCNR, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Reply by ●October 19, 20102010-10-19
On Oct 18, 11:29=A0pm, "Michael A. Terrell" <mike.terr...@earthlink.net> wrote:> "k...@att.bizzzzzzzzzzzz" wrote: > > > On Tue, 19 Oct 2010 07:20:50 +0300, Paul Keinanen <keina...@sci.fi> wro=te:> > > >On Mon, 18 Oct 2010 18:29:04 -0500, "k...@att.bizzzzzzzzzzzz" > > ><k...@att.bizzzzzzzzzzzz> wrote: > > > >>>Mostly I just use a computer-controlled scanner. If there is a nasty > > >>>emission somewhere it'll find it. Sure, I can't quantify it here in =the> > >>>lab but after a couple of decades on the beat you know what'll cause > > >>>problems, just like an older cop can look a guy in the eyes and tell > > >>>that "he dunnit". > > > >>Scanner? =A0Does it cover the entire range (30mHz to a few GHz)? > > > >BTW, what kind of antennas are you using at 30 milli Hertz ? > > > Big ones. > > > >Even if 30 MHz .. multiple GHz is intended, getting a sufficient > > >antenna bandwidth is a challenge. > > > That's the least of the problems. > > > >At 30 MHz the wavelength is 10 m, so doing the measurement in the far > > >field requires a big room. > > > Or far out in the field. > > =A0 =A0Like the outdoor antenna range we used at the original CE plant in > Cincinatti. > > -- > Politicians should only get paid if the budget is balanced, and there is > enough left over to pay them.- Hide quoted text - > > - Show quoted text -sounds like some of you guys are confusing conducted with radiated emissions tests. read the fcc part 15 regs for ism band. by "scanner" i assume the reference is to a SA. 3mh ... something doesn't sound right ... lost in the phase noise .... haha!
