Post by thread:[PICLIST] MCU circuits and the FCC

And you can read part 15 at http://hallikainen.com/FccRules On Sun, 18 Jun 2000 13:05:08 EDT Ed Edmondson <spam_OUTEaejrphdTakeThisOuTAOL.COM> writes: > John, > > Have a look at FCC Part 15? It covers most of the conducted and > radiated > emissions limits. AFAIK, if you sell it has to meet these specs or > the FCC > can put you out of business. > > Ed ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: dl.http://www.juno.com/get/tagj.

From sec 15-103, Exempt Devices, it appears that if I am under 1.7Mhz, and operate from a battery, but not operate while recharging from AC adapter, I could be exempt? Copied from Hallikainen.com: ' (h) Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines or contain[[Page 670]] provisions for operation while connected to the AC power lines. Digital devices that include, or make provision for the use of, battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, do not fall under this exemption. '

On Sun, 18 Jun 2000 14:58:35 -0700, you wrote: >>From sec 15-103, Exempt Devices, it appears that if I am under 1.7Mhz, and >operate from a battery, but not operate while recharging from AC adapter, I >could be exempt? > >Copied from Hallikainen.com: >' >(h) Digital devices in which both the highest frequency generated and the >highest frequency used are less than 1.705 MHz and which do not operate >from the AC power lines or contain[[Page 670]] provisions for operation >while connected to the AC power lines. Digital devices that include, or >make provision for the use of, battery eliminators, AC adaptors or battery >chargers which permit operation while charging or that connect to the AC >power lines indirectly, obtaining their power through another device which >is connected to the AC power lines, do not fall under this exemption. >' But presumably the 1.705MHz includes harmonics? If I fed a 74AC device with 1MHz and connected the output to a long wire I'm sure it would radiate like hell.

John Pearson wrote: > > >From sec 15-103, Exempt Devices, it appears that if I am under 1.7Mhz, and > operate from a battery, but not operate while recharging from AC adapter, I > could be exempt? I doubt it. The key here is 'highest frequency generated'. Even though your xtal says 1.7 MHz, there are still harmonics, and they'll look at at least the tenth harmonic of your fundamental. I wonder who's using 1.705 MHz and bribed ^H^H^H^H^H^H talked the FCC into this exemption? Phil -- Phillip M. Vogel, President | "It's not what you've been taught, Bartal Design Group, Inc. | it's what you've learned." (me) 318 Marlboro Road | +1-201-567-1343 FAX:+1-201-568-2891 Englewood, NJ 07631 USA | .....phillipKILLspam@spam@bartal.com

I think the FCC thinks of 1.705 as the top-end of the AM band, and so they set their limit there. btw: I was reading Part 15 where it said the exemption was for products which _used_ no frequency about 1.705 MHz. One message in this thread asserted that would include harmonics of the PIC clock. I am sure that the term "used" is defined explicitly in the regs somewhere. Does anybody know where? Bob Ammerman RAm Systems (high performance, high function, low-level software)

On Wed, 21 Jun 2000 16:55:02 -0400 Phillip Vogel <phillipKILLspamBARTAL.COM> writes: {Quote hidden}> John Pearson wrote: > > > > >From sec 15-103, Exempt Devices, it appears that if I am under > 1.7Mhz, and > > operate from a battery, but not operate while recharging from AC > adapter, I > > could be exempt? > > I doubt it. The key here is 'highest frequency generated'. Even > though your > xtal > says 1.7 MHz, there are still harmonics, and they'll look at at > least the > tenth > harmonic of your fundamental. > > I wonder who's using 1.705 MHz and bribed ^H^H^H^H^H^H talked the > FCC into > this > exemption? > > Since 15.103(h) specifically states "digital device", which obviously use pulses, which have infinite harmonics, I believe the exemption refers to the clock frequency, discounting harmonics. The actual rule is available at www.hallikainen.com/cgi-bin/section.pl?section=15.103 It's interesting that there is no Federal Register history listed at the bottom of the rule. A search of the Federal Register (1994-present) turns up only mentions of the rule, not any real discussion. A search of the FCC's website for mentions of the rule (using CiteSearch at http://hallikainen.com/FccRules) also turns up nothing. It'll take a bit more research (probably thru the Federal Register) to find some discussion regarding the writing of the rule. The choice of 1.705 MHz is, I believe, due to it being the top of the AM broadcast band (see 73.14 at http://www.hallikainen.com/cgi-bin/section.pl?section=73.14). I'm surprised there's not FR mention in the rule of the expansion of the AM broadcast band. So, my guess is that the interpretation that digital devices with a clock of 1.705 MHz or less with no connection to the AC power line is correct. Harold ________________________________________________________________ YOU'RE PAYING TOO MUCH FOR THE INTERNET! Juno now offers FREE Internet Access! Try it today - there's no risk! For your FREE software, visit: dl.http://www.juno.com/get/tagj.