§ 15.219 Operation in the band 510–1705 kHz.
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(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.[b](a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.[/b]
(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be deomonstrated by measuring the radiated emissions.

§ 15.221 Operation in the band 525–1705 kHz.
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(a) Carrier current systems and transmitters employing a leaky coaxial cable as the radiating antenna may operate in the band 525–1705 kHz provided the field strength levels of the radiated emissions do not exceed 15 uV/m, as measured at a distance of 47,715/(frequency in kHz) meters (equivalent to Lambda/2Pi) from the electric power line or the coaxial cable, respectively. The field strength levels of emissions outside this band shall not exceed the general radiated emission limits in §15.209.

(b) As an alternative to the provisions in paragraph (a) of this section, intentional radiators used for the operation of an AM broadcast station on a college or university campus or on the campus of any other education institution may comply with the following:

(1) On the campus, the field strength of emissions appearing outside of this frequency band shall not exceed the general radiated emission limits shown in §15.209 as measured from the radiating source. There is no limit on the field strength of emissions appearing within this frequency band, except that the provisions of §15.5 continue to comply.

(2) At the perimeter of the campus, the field strength of any emissions, including those within the frequency band 525–1705 kHz, shall not exceed the general radiated emission in §15.209.

(3) The conducted limits specified in §15.207 apply to the radio frequency voltage on the public utility power lines outside of the campus. Due to the large number of radio frequency devices which may be used on the campus, contributing to the conducted emissions, as an alternative to measuring conducted emissions outside of the campus, it is acceptable to demonstrate compliance with this provision by measuring each individual intentional radiator employed in the system at the point where it connects to the AC power lines.

(c) A grant of equipment authorization is not required for intentional radiators operated under the provisions of this section. In lieu thereof, the intentional radiator shall be verified for compliance with the regulations in accordance with subpart J of part 2 of this chapter. This data shall be kept on file at the location of the studio, office or control room associated with the transmitting equipment. In some cases, this may correspond to the location of the transmitting equipment.

(d) For the band 535–1705 kHz, the frequency of operation shall be chosen such that operation is not within the protected field strength contours of licensed AM stations.

[56 FR 373, Jan. 4, 1991]

That's fine except those are "alternatives" to the general emission limits specified in part 15.209.

http://www.gpo.gov/fdsys/pkg/CFR-2011-title47-vol1/pdf/CFR-2011-title47-vol1-part15.pdf
47 CFR Ch. I (10–1–11 Edition)

§ 15.215 Additional provisions to the
general radiated emission limitations.

(a) The regulations in §§15.217
through 15.257 provide alternatives to
the general radiated emission limits
for intentional radiators operating in
specified frequency bands. Unless otherwise
stated, there are no restrictions
as to the types of operation permitted
under these sections.

And again you are misinterpreting the CFRs to suit your agenda. Read them
again carefully.

QUOTE: 15.215 Additional provisions
to the general radiated emission limitations.

(a) The regulations in §§15.217
through 15.257 provide alternatives to
the general radiated emission limits
for intentional radiators operating in
specified frequency bands.

Those CFRs apply to emission limits,!!! There are no emission limits for intentional radiators unless they relate to carrier current and leaky coax systems used by educational facilities. You are again taking the intended scope of those regulations out of context to amend something that doesn't exist. Show me the emission limits that they provide an alternative for.

Right...when you use the 100 mw, 3-meter rule, there is no radiation limit within the broadcast band. But there is a radiation limit for signals from the transmitter outside the band (spurs, harmonics, etc.). The argument about whether the wire in a loading coil and/or the length of a grounded mounting pole is part of that 3-meter length restriction has still not been settled.

Dave

There are general emission limits for ALL intentional radiators, specified in part 15.209, and I quoted them in my very first post. They are, for 0.490–1.705 MHz, 24000/F(kHz) uV/m at 30 m.

As is explicitly said in part 15.215, part 15.219 provides an "alternative" to part 15.209.

A worst case analysis might show that part 15.219 is more lax than 15.209, which may be why everyone seems to think it is 'the requirement'. However, the FCC says if you meet 15.209 then 15.219 is moot, or vice versa, since either are 'compliant'.

It provides an alternative means for making emissions measurements, but it does not override the 100 mW input limitation. Nothing overrides that requirement. Emissions relates to field intensity, not power input. An alternative means for making field intensity measurements is not an alternative for power input regulations.

Read Dave's post.

Pete

You have what's an 'alternative' to what backwards. Part 15.219 is an "alternative" TO making emissions measurements in part 15.209.

I did and it's perfectly fine. "When you use" part 15.219 there are no in band radiation limits, because part 15.219 is an "alternative" to 15.209.

By the same token, "When you use" part 15.209 you need not worry about the "alternative" part 15.219, because you aren't using it.

Here, http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf Go to page 10 and the 525-1705 kHz section of the table. Those are your choices and you have 4 covered by parts 15.209, 15.221, and 15.219.

I think the 100 mw, 3 meter rule was intended as an alternative to taking emission measurements for people who don't have access to a calibrated field intensity meter. But if you are going to pump in more than 100 mw and/or use a longer antenna and ground lead, then you need an FIM to check compliance with the rules for emission limitations.

Dave

At 2400/F = uV @ 30M a transmitter operating at 1700kHz will be limited
to about 14uV @30 Meters. That is actually less than the allowable field
intensity readings for operation between 1705kHz and 2.173MHz (15uV @
30m).
The rules also specifiy thatout of band radiation for transmitters operating
in the BCB is required to limit out of band spurious emissions by 20dBc. A
20 dB disadvantage seems rather severe to me.

Using that loophole places a part 15 transmitter at a extreme disadvantage
to a transmitter running 100mW input power, and the max. allowed 10 foot
antenna-feedline-ground lead system.

It was claimed "this was written into the rules" to allow experimenters to more
easily meet the rules. Unfortunately it is far more simple to use a volt and
millivolt meter, and a ruler, to determine compliance, vs. a several thousand
dollar investment in a field strength intensity meter, which very few experimenters
own, are capable of operating, or are even aware of. Maybe, if you have a buddy
who is a chief at an AM station, you can beg and borrow one for the day. But
at 14uV @ 30 meters why bother?

And I'd bet those "Relaxed" rules are closer to those imposed on non
intentional or incidental radiators.

Pete

Yeah, that's the way I heard it too. Supposedly there was some kind of 'back calculation' and the FCC expected those 'hobbyist measureable' limits would come out about the same. At first, though, ground and feedline weren't included but when clever DIYers began twiddling with those to increase range they were added to bring it back down.

You mentioned questions about base loading the antenna and I heard questions about top hats. If needed, I suspect those might get 'resolved' on the same basis. I.E. Anything that actually 'works', and becomes widespread, is likely to end up with some kind of rules revision because limiting range is 'the point' of it. Yeah. I was postulating there might be an 'indirect' way of checking 'ballpark' compliance by comparing range to something which, at least, 'should be' compliant. That obviously wouldn't fly for certification but might be considered a good faith effort. Actually, I was simply on-the-spot speculating that if the DC pentode jobs had significantly less range than Tom's latest 'underpowered' 72 mW LM386 brick osc transmitter then they were probably okay, despite the apparent plate power.

It's probably moot for most people who just want to broadcast to some radios in their own home, as long as they apply common sense.

If I was going to play by the rules, a capacitive top hat is exactly what I would do. All ten feet for the radiator--do what it takes to increase the radiation resistance.

I suppose the radius of the hat would have to be added, but it still sounds like a winner to me. The RangeMasters get around the loading coil debate by winding it on a toroid, and internal to the transmitter enclosure. And, if by chance the base mounted transmitter ends up on top of all tall steel structure.... or in a salt marsh...

it really comes down to the whim of the local field inspector when an issue arrives.

Pete

Precisely!

Dave

I'm not sure what the value is in comparing bands, because they differ.Part 15.219 also specifies -20 dB out of band. Its worded a bit differently but I think the net result is the same: "(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier." Near as I can tell its part 15.219, specified as an "alternative," that's the 'loophole'. For home builders part 15.23 is the real 'loophole' because the 'requirement' is simply "good engineering practices to meet the specified technical standards to the greatest extent practicable." Of course, if you stuck a 200 foot antenna on a 200 Watt transmitter it would be dern hard to claim you're even 'trying'.

Actually, I think part of the problem is that people seem to believe that if their homebrew, or whatever, is 'compliant' with whichever part they've picked then they should be 'immune' to scrutiny: the "Hey, I'm legal" argument. They either forget, or don't know, that no amount of 'compliance' excludes one from part 15.5 "(b) Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused..." I.E. if the FCC is there because of a legitimate complaint then "Hey, I'm legal" is not a defense to part 15.5.I'm confused with what you mean here but if you're referring to what I said it was that part 15.219 was carved out to cater to those who can't measure emissions. I got that from a thread at part15.us (not an FCC site) in a post that allegedly quoted an FCC official and get the impression part 15.219 limits were based on what they saw in existing devices at the time, like phono oscillators and baby monitors, but they didn't envision hot shot amateurs pushing the envelope, arguably a 'mistake'. So, if you stick it on a pole with a hotshot antenna and sink in a hefty ground plane you can probably radiate more than a little indoors grey box dangling a wet noodle wire antenna, but the 'pipsqueak' thing is really what the FCC 'had in mind'.If you mean part 15.219 I don't know how one would 'compare' because non-intentional and incidental radiators are governed by emission measurements. For example, one class of 'unintentional radiators' that part 15 spends a lot of text on is 'digital devices', with your PC being an obvious example. There simply isn't any 'power to the RF final' equivalent but you don't want all the radios in a 30 meter radius to suddenly go dead because someone flipped on their notebook.

This is a good discussion but we've gone into a lot of things so it might be useful for me to clarify what I originally said and meant. I was looking at the LM386 modulated brick osc who's total circuit power is 72 mW and, so, to that extent part 15.219 compliant. At the same time we have the dual control pentode jobs that would appear to have over 100 mW plate power. I simply meant that while it appears the DC pentode jobs don't meet part 15.219 they might meet part 15.209. That wasn't to say part 15.209 is 'better' or that part 15.219 doesn't 'allow' more range. I was just speculating they might be 'compliant' with a different section because they have a more limited range 'as we normally say we're using them with a 10 ft wet noodle dangling off the plate'.