Part of the concern with connecting audio and power is -- as shown in my tests, connecting these items drastically increased the field strength of the WH 3.0 transmitter. By many times. Taking it from being an illegal output, to being an extremely illegal output. I don't have the numbers in front of me (they're posted in another thread) but if I remember it was something like 1100 uV/m at 3 meters, and with an audio cable plugged in it jumped to over 4000 uV/m. That is a significant amount over legal, and in FM-land field strength is the ONLY test for legality. And this was on a transmitter not even connected to power, just internal batteries.
AM seems to be just chock full of gray areas. If you're at 100mw at the final and your antenna/ground is 3 meters or less you're OK. The trouble is in the definition of ground. Clearly a wire screwed to the ground lug and run 30 feet is not going to be legal. Now, if you're using something like a Procaster or a Rangemaster I assume certification tests were done with power connected since they don't run on batteries. In my own brief test when I was first setting up my Procaster I got NO difference in field strength at 30 meters when the transmitter was connected to AC power and a small portable plastic cheap mp3 player than I did when it was connected to it's supplied AC adapter and the computer sound output. FWIW I also showed NO continuity between the ground lug on the transmitter and any of the audio or power connecting terminals.
But quite decisively connecting a Whole House 3.0 transmitter to ANYTHING, including a power cable, or an audio cable greatly increases it's output. By a factor of about 4 times. Brief testing with the Decade CM-10 (not in a strict set up field test like I've done for the WH 3.0) shows the SAME THING happens when the audio cable is plugged in even though it was running on AC power.
TIB
Not poking the FCC in the eye I'd assume they allow for this? If not was it a mistake on their part years ago when the rules were made for part 15 Radio on FM? Yes AM is better for as long as you follow the 100mW and antenna/ground rules you should be fine. I'm sure they thought of folks who can't put up an outside antenna when they made the rules. So keep the antenna no longer than 3 meters you could build your own inside antenna and still be legal. Doing so for FM could make you illegal. That said I sort of feel like Timinbovey where I could advertise my station on a bulletin at the library or put a sign in front of my driveway. Where as doing so on FM could land you in trouble. I'm not sure I'd advertise in the newspaper though based on the fact that the station in Origin got in to trouble that way and also the person with the Talking House AM Transmitter got in trouble for 20 mW over the limit. I don't have a watt meter for AM. Should I buy one if I decide to advertise in a paper? How accurate are they? Do I connect it to the Outdoor input or can I connect it between the wire terminal and the wire or metal antenna that is built? Maybe I'll ask Daniel Braverman about that although I am pretty sure this TX was thoroughly tested for 100mW out. Station8 has one and his is something like 92 mW. So I'm sure because of that incident iAM is running them all under 100mW and only on a special occasion would they max it for a customer at full 100 mW. I really don't want to damage this new transmitter anyway. Wrong impedance and high SWR (although it does have a tuner) can cause damage to it really fast. Im sure if I take good care of it this transmitter should last a very long time.
On FM radiating power or audio leads are a just about moot from the FCC’s point of view. It is the responsibility of the transmitter operator to be incompliance with the part 15 field strength limit. If an agent takes a field strength reading and the transmitter is over the limit, they can issue a NOUO. I don’t necessarily think that is fair, but that is how it works.
On AM, compliance with 15.219 is largely dependent on how the inspector interprets the rules. Again, I don’t necessarily think that is fair, but that is how it works. If a part 15 AM transmitter is not on the ground and the inspector wants to count the audio and power leads as part of the ground, they probably could because 15.219 is quite vague. So, for example, that really sucks for people who live in non-ground floor locations because a strict or mean inspector could say the building’s wiring is part of the ground lead and issue a NOUO, even for a transmitter that is certified with a 3 prong power brick. (15.219 does not define ground lead, nor does it make any difference between a radiating vs non radiating ground.)
Even if an FM transmitter complies with 15.239 or an AM transmitter complies with 15.219, in theory, a NOUO could be issued for some vague reason under 15.5.
There is no guaranteed way to be 100% certain something is a completely legal unlicensed operation. (As an aside, even licensed operators get fined for breaking rules.) The best advice I can offer is not to do anything that could fall in a grey area or do anything that seems legitimate but noticeably increases range.
... 15.219 does not define ground lead, ...
But the principles of physics DO so.
... nor does it make any difference between a radiating vs non radiating ground. ...
Any/all true r-f grounds and counterpoises, by themselves, do not produce useful far-field radiation.
Examples of a true r-f ground reference are:
- buried ground rod(s)
- buried radial wires
- radial wires on or elevated above the earth
- buried, metallic pipes leading to the cold water supply
However the audio, d-c power, and "lightning ground" conductors of an elevated AM/FM-band transmitter between that transmitter and such r-f grounds WILL produce useful radiation, unless some means is in place to prevent it.
Other things equal, the unfiltered audio/d-c power/"lightning ground" conductors attached to an elevated AM/FM transmitter need NO connection to a true r-f ground in order to produce a very significant effect on the fields radiated by such transmit systems.
Rich said - "...unless some means is in place to prevent it."
Talk about that.
and your understanding thereof are all you should need.
It should be legal to build your own inside antenna for a Talking House or iAM transmitter as long as you don't exceed 3 meters. The Talking House and iAM has a brick 3 prong power supply. This should not violate any rule.
I'm not going to do "due" research on some claim you made.
I have my own way of neutralizing radiation on an elevated antenna, but I have no plans of posting it here/now; you're the one that made the claim that there's a "means" of doing it, I already know what I know, I wondered what you were referencing.
What the hell's wrong with you?
Tim: The Procaster was tested with cables and a 30" ground lead attached.
If a FCC inspector comes and the transmitter operator talks to the inspector the way post 19 is written I could see a NOUO being issued out of spite.
The wording of 15.219 (b) is open for interpretation, and when an inspection taking place the only interpretation that matters is how the inspector interprets it.
“The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.” (47 CFR 15.219 - Operation in the band 510-1705 kHz, (b))
What is an antenna, how should the length of an antenna be measured? Electrically, three 110” wires bonded at the top and bottom on a triangle frame making a skirt with a diameter of 12” is almost identical to a piece of conductive pipe 110” long. But an inspector could take out a tape measure, measure each wire separately, add them together and call the three wire skirt antenna 330” long, while there would be no argument that a pope 110” long is less than 3m. A 110” pipe antenna with a wire rod top hat consisting of 4 12” rods is only going to radiate over the 110” vertical portion, with the top hat adding capacitance to better match the transmitter, but an inspector could use a tape measure and come up with a total length of 158”. So the safest antenna is something where there is no ambiguity of how to measure it.
There are NOUO’s for elevated installs where there was a short wire from the transmitter to a metallic support structure, and the inspecting agent decided to say the structure was part of the ground lead, because the structure was part of the path to earth.
On the other hand, I can’t see a NOUO being issued for buried ground radials because all they are doing is enhancing the local ground conductivity, and as long as they are in the dirt, they are part of the earth/ground.
The power supply on the talking house is a bit confusing to me. I would think when the talking house was certified they must have used the 3 prong power supply so it was certified as a system. At the same time, a manufacturer of a different transmitter in the manual suggested an elevated install that NOUO’s were issued for, so the idea of an entire system (transmitter, accessories, manual) being certified as a package does not seem to be the case. So while I hope the talking house with the provided power supply is compliant I could see an inspector calling the power cord part of the transmission line, antenna and ground lead length and issue a NOUO. I think a problem is the burden of complying with the rules as interpreted by the inspector falls on the operator, not the manufacturer.
Here is what I think an indoor or elevated strictly 15.219 compliant transmitters would be like:
1. Fed with a non-shielded no path provided to ground optical cable. (for some reason some fancy boutique optical cables have a shield, don’t use those)
2. Powered by a battery
3. Antenna has 2 leads 1.5m long.
4. Installed on a non-conductive support structure.
5. The only link between the transmitter and ground would be incidental capacitive coupling
The battery power aspect is annoying, but a power lead could provide a “sneak” connection to ground. Even using a DC-DC converter to isolate the entire mess could cause measurable capacitive coupling between the RF section and the power lead. (15.219 just says ground lead, it does not specify some minimum RF impedance/chocking value required for something not to be called a ground.)
I would like to think no one doing an indoor or non-ground level install would need to go through all that trouble, but as was shown by enforcement in OR, some inspectors are very strict in how they interpret the rules. The more attention a part 15 operation draws the more likely someone will take notice or the FCC will show up.
I am pro micro broadcasting. I am just concerned by a cavalier attitude to push the rules to get more range and an apparent belligerent attitude directed to the FCC. Those two things together feed people like the enforcement in OR to be hard-asses.
They may even take the fact that some folks have to use a power strip to plug a Talking House AM Transmitter into in order to operate. All it takes is for someone to notice you and to complain. However I think too it depends on the state your in as well. I still stand behind that NY, NJ, CT, FL and parts of California may be places to avoid for hobby Radio due to the Pirate Radio issues in these locations. Michigan (Not close to Detroit), TN, AL, OH, ARK, IND you may not have issues if you follow the rules. We're talking real part 15 here and no fudge factors or overpowered TX's of any type.
I am not legally trained nor so licensed but as an observer I have opinions. Recently I dined with a family friend who is a highly regarded attorney and the topic of laws and regulations was discussed. He said something which I found interesting. Essentially "Laws and regulations are usually written to be general and subject to interpretation." My observation is that this is probably to avoid trying to list all specific conditions to which the law applies which would be impossible.
While a consultant to the FDA regarding medical device regulations I learned the difference between "standards" and "specifications". Standards specify the performance of a device where specifications detail the design of the device. For example, there were incidents where devices on wheels would tip. The standard approach is to rule that the device shall not tip when a force of X Newtons is applied at a height of Y meters. This leaves the designer free to design as they want as long as the standard is achieved. The unused specification approach would have been to rule that the wheels must be spaced to span an area equal to X times the height of the device which does not allow for design freedom.
So, what has this to do with anything? I suggest that the Part 15.219 is written as a specification and not a standard because it describes limits applied to design rather than performance, yet it does so without specifying the detailed design which puts it in a gray area. Therefore it is left open to interpretation since the specifics of transmitter/antenna design are not detailed but are limited. The intent of 15.219 is to restrict the radiated energy (a performance issue) and this is done by limiting the antenna, feed line, and ground lead by length and the power. It is worth noting that the rule does not mention loading coil use which tremendously affects radiated energy (a standard) and an inspector, realizing this, could count the length of the wire in the coil as part of the antenna length in order to reign in the field strength. (There was an opinion, as I recall, from an FCC engineer that the wound wire length doesn't count but I am just using this as a general example.)
Parts 15.209 and 15.239 are standards since the designer can do whatever they want as long as the performance (field strength) criterion is met, but this is beyond the ground discussion.
It does not appear to me to be useful to try to guess what an inspector might do re interpretation beyond what would be an obvious infraction of the rule. If the rule writers had specifically stated that billboard frames, protective ground wires, and audio/power leads were part of the ground lead then that would imply that other conductors to ground not specifically listed would be acceptable. Thus, as was mentioned earlier, the rule is written subject to interpretation. It is not satisfying but it is how things work.
I do pay attention to the length limits but am not worried about the power and audio leads. I know of no case where such leads were mentioned in a NOUO but if an inspector comes here and tells me otherwise then so be it. To worry about every conceivable possibility ruins the whole hobby. Do your best to follow the rules in good faith and have fun!
Neil
For your insight and wisdom.
At one time I purchased a metal folding chair for use in my room/studio and came home one day to find the chair missing.
Upon tracking the chair to my step-brother's room, I retrieved it and scotch-taped a Notice of Law to the back of the chair:
"No person below the age of 16 may use this chair for any purpose."
At the time I did not consider the fact that persons below 16 have birthdays and eventually reach "legal age" for chair taking.
Like the certification tests for the Procaster are quite complete and included the use of power cables with the supplied adapter and the cable from the studio interface box to the transmitter. See:
https://fccid.io/pdf.php?id=2042788
Also, it comes to mind that a typical 12V DC power supply (wall wart) is in fact isolated from the house wiring and the rest of ground due to the fact that it is a transformer. Now, this may not apply to the fancy new switching style power supplies, nor wall warts with a third pin for ground at the socket. But the power supply with my Procaster is a typical wallwart transformer style, so it's a transformer with rectifiers and filtering. And in fact a quick check moments ago shows NO continuity between the power jack to the transmitter and the power pins to the wall socket. So, unless there's a ground created by induction these babies don't get to ground through that style of PS.
Certainly a transmitter elevated and grounded to a metal support structure would be over the limit, as that metal structure radiates.
The compareson between FM transmitterw will be interesting, as the WH 3.0 ran on batteries, and was used on batteries in it's certification, so no cable was used. The certification paperwork in many places states the transmitter operates ONLY on batteries and that the port used for outside power has been disabled and does nothing, which is clearly not true at least for the unit I received and those advertised on their website.
I realize comparing AM and FM units is not only apples to oranges, but more like Pop-Tarts to pomegranites. And the WH 3.0 is an even bigger distraction as it can run on batteries, and was in fact certified on battery power, where the Decade CM-10, which I hope to get to the field in the next few days, requires an attached power supply and was certified with a power supply.
TIB