The Bulletin Bulletin from MRAM is indeed an eye opener.
Viewing the ATU as "The Final Stage" out at the end of the transmission line (up to 300' coax) really makes better logic than the awkward way we have been fretting over "100mW to the final RF stage", where we have mistakenly believed this to be the final RF amplifier.
It is much more sensible to state that we have "100mW Output Power" (from the final RF stage), doing away with the nit-picking over 60% efficiency or whatever small slivers of energy get lost in that final RF amplifier.
This more convenient way of viewing and measuring our part 15 transmission systems has become the new standard. It has been so declared.
"This satisfies many questions regarding the legality of mounting the ATU up on a pole whereas the coax shield is grounded through the transmitter chassis."
Well you might be satisfied by some iPad message from a personal iPad but I'm not.
How about requesting to see their certification documents which will include photos of that thing sitting up 300 feet when it was certified.
Isn't it curious that the certification documentation to both the TH/iAM and this infospot unit are mysteriously missing from the public database???
And you didn't ask for evidence of certification? Did you mention that it is missing off the FCC website?
And where is it that the FCC actually says the coax and antenna atu are the final stage? As a matter of fact, where did it ever say that in the certification documentation for the TH/iAM?
All I've seen are people quoting something without validation or something backing it up. Nothing from the FCC, documentation that is missing, especially to certain units, answers from iPad's and not company email addresses, and your going to say "okiedokie I'm convinced"???
Well good luck!
RFB
15.219 (a) The total input power to the final radio frequency stage shall not exceed 100 milliWatts.
Is an ATU a "radio frequency stage"? Obviously.
It was there all along.
"Viewing the ATU as "The Final Stage" out at the end of the transmission line (up to 300' coax) really makes better logic than the awkward way we have been fretting over "100mW to the final RF stage", where we have mistakenly believed this to be the final RF amplifier."
There is a HUGE difference in what we "view" as "better" versus the actual view of the FCC, to which as yet is no proof that the FCC has this same view of this issue.
All we have are quotes from end users, an iPad email from a company vice president who is not an FCC field engineer or lawyer with experience in interpreting the rules, and missing crucial documentation from the OET database, and nothing from these companies in the way of certification documentation.
Wouldn't you fellas be more comfortable in seeing the actual certification documents with the photos showing this atu 300 feet up and being approved?
That sure would satisfy my concerns far more than just words or iPad emails.
I'm surprised that's all it takes, an iPad message to convince you guys that it's all ok because of what some company vice president says on an iPad message, rather than be convinced from actual official documentation of that being certified for atu's sitting 300 feet in the air.
Well let us know how it goes!
RFB
That doesn't mean anything Carl. All it is saying is a power level limitation. It doesn't clarify that the final stage is either an active element circuit, or a passive element such as a coupler or ATU.
Again this goes to the old argument of rule clarification and correct interpretation.
I don't know about anyone else but until the clarification comes directly from the rules and clearly defines what a final RF stage would be, I wouldn't run risks just because of rumor or 50/50 interpretation chance.
It's your call.
At least for me, until I see something from official sources and not copy paste messages, I won't take the chances..and neither should anyone else.
RFB
"Not taking chances", it seems to me, requires two things:
First, we should interpret what rules there are to the best of our own ability;
Second, we should keep a record of our attempts to gather more official input from legitimate sources.
It doesn't get more rational than that.
It would be great if the ATU is considered to be the final stage and the coax run is permissible under 15.219 but I have my doubts about this. The ATU is a tuner comprised of passive components. It matches the antenna to the transmission line and so does a base loading coil. If the ATU is considered the final stage then, by function, so is a base loading coil and a long run of coax would be allowed by this logic.
My thoughts are in line with the comments of RFB in that the determinant of this is the FCC. The response of the manufacturer's representative is encouraging but it could be wrong.
There is a problem with asking the FCC about this in that a ruling could ruin the impression that the long coax run is OK but for certification a copy of the user's manual is submitted and if the manual is acceptable to the FCC and it describes the use of a coax feed line then it would seem that this is OK. A copy of the actual FCC certification documents would be a great help with this.
Neil
TRUE, RFB and Radio8Z, without the FCC certification documents stating in concrete terms what we only know now by hearsay, we are "spinning our wheels" or "whistling in the dark".
But as a side venture I presently believe that an ATU is an "RF stage" and that a loading coil and its accompanying tuning method is in itself an ATU.
In my present world, as yet un-overturned, I believe that the one time that the input to the final RF amplifier stage needs to be kept at 100mW is when there is only a straight wire antenna on the other side and no form of ATU.
But let's have a sobriety check point......
Where the milliWatts are concerned, we are talking about very tiny amounts. And where the length of a transmission line is concerned, small lengths in the typical home installation. Lengths whose contribution to potential radiation is barely measurable.
Proof of our holiness in regard to part 15 responsibility lies in the intensity with which we explore our "biblical studies".
" A copy of the actual FCC certification documents would be a great help with this."
That would certainly put the nail in the coffin and seal the deal for sure.
Again, isn't it interesting that those documents are missing out of the database, and not a single one of those companies are offering their copy up or even have a copy posted on their websites.
The only true thing that can put this to rest is that original certification documentation or a copy of it, with all the nice pretty pictures REQUIRED for certification.
Ahh the one thing that solves all the questions is the ONLY true answer and its the ONE thing that just so happens to be missing from a database where everything else is currently parked.
Until that time such information is available, it's just guessing and risk taking.
RFB
Taken from the recently obtained information through an FOIA request made by Robert (kc8gpd):
"For suspected unlicensed operation in the 510 to 1705 KHz (AM Broadcast) band, there are similar requirements. Section 15.209(a) establishes that intentional radiators in this band need not be licensed if they generate a field strength of less than 240001F microvolts /meter, where F is in Kilohertz, at a distance of 30 meters. As an example, a station near the middle ofthe AM band (1000 Kilohertz) would be allowed 24 microvolts/meter at 30 meters from the antenna. There are two exceptions to this rule (15.219 and 15.221) and because there is no field strength limitation associated with operation under 15.219, an inspection is generally required to determine with absolute certainty that an AM broadcaster is in violation of Part 15.1, and therefore unauthorized."
Now if these transmitters with ATU's were approved under the general emission rule 209, which does not specify anything about using a coax or even an antenna size limit, then I can see them being certified with a 300 foot coax feeding an ATU sitting 300 feet up in the air.
Then again, measuring for 24uV/F at 30 meters when its another 202 feet beyond that measuring point above the measuring antenna would be interesting to see as well. BTW, 30 meters is 98.4252 feet.
According to the iPad message from the company vice pres, that infospot, which is basically a TH/iAM, is certified under 219.
Well...as the quoted section from the field manual the FCC agents use, it's going to be determined by that field agent if your 300 foot high up ATU is ok or not.
Sure would be nice to know for sure ahead of the toss it to the wind route.
RFB
Could it be that the certification of transmitters is being played in a loose way by some manufacturers?
One case in point: My Schosche FMT4R Certified FM Transmitter has 14 frequencies, two of which are 87.7 and 87.9 mHz.
Sweet deal?
I opened the door. The VP of the company producing the questionable equipment says it's FCC approved as stated. And yes, I did include the statement "up on the pole" when I questioned its use.
If he is not being up front and truthful, the burden is on him.
RFB, you now have a name a number and email for this person.
Perhaps you can follow up with him on this matter. If he realizes more than one individual is questioning this he may be forthcoming with additional info.
By the way, the first response from him was from his company email account, the second from his IPAD.
Submitted by mram1500 on August 16, 2012 - 20:40. The InfoSpot system is built around the IAM/Talking House transmitter and ATU. ... They specifically advertise the system as legal under Part 15 rules, placing the ATU (antenna) up that pole with up to 300 feet of coax. They imply the legality (FCC acceptance) of this with their advertisement. Please view INFOSPOT SYSTEM information.
If so, then notice Item 6 in the table on the last page of the instruction book for the ATU shown on the iAM website as of a few minutes ago (link below).
Seems as though they recognize that running a long conductor from the ATU ground wire connector terminal to the examples of "earth grounds" they list can conflict with §15.219(b).
http://www.iamradio.net/pdfs/OutdoorAntennaInstructions.pdf
Where he wrote "And where the length of a transmission line is concerned, small lengths in the typical home installation. Lengths whose contribution to potential radiation is barely measurable."
True, the powers and intensities are minuscule but when compared to the low power radiated by the antenna they can be significant in comparison and they are measurable.
While setting up my outdoor antenna I used a 15 foot transmission line between the transmitter and the base of the antenna. This was necessary for the rough-in adjustment because if I was near the antenna it was pulled off resonance and this adjustment plus measuring the final input power were not accurate. The final adjustment was a bit more complicated than this and involved measuring the field strength while the antenna coil was tuned.
I have a large loop antenna with a FS meter attached which I built and using this determined that there was a relatively strong RF field coming from the transmission line.
Does this mean the transmission line from the TH to the ATU radiates? I don't know but this suggests that it could.
Neil
"Perhaps you can follow up with him on this matter."
That's a great idea. Hopefully some missing pieces of the puzzle can be provided.
My strong points about all this isn't at you MRAM, it's at the answers all of us are getting, which that and the specific missing certification documentation..well I smell a fat rat in the house.
Or there are several small ones grouped together, still a stink is a stink.
Asking questions about a product, especially these with coaxes and ATU's with claims being legal to mount 300 feet up is not an unreasonable thing to do. Is it?
I will be convinced to slam down the $$$$ for one if proof is provided, that is official proof, these are certified for that ATU at 300 feet.
I think a lot of us would! 🙂
RFB