This is interesting, I've not seen this post before..
Its from six year ago, by member Seankw40, but he attempts to explain how it was that the TH Range Extender had ever received its certification. Below are select extractions specifically about the matter (the original is a lot longer). I'm not quite sure I grasp it, but it's the only time I recall anyone even attempt to explain it before.
There is another old post here somewhere where Ermi Roos (I think) had argued it had been only due to clever wording that certification had been accomplished... -- I'll try to track that down to compare later, z
But as for Seankw40's take on it as highlighted below, I ask; Does it hold any merit?....
https://www.part15.org/community/antennas/iss-range-extender/paged/3/#post-54543
... after going over all the rule it was clear how the company was able to get around the rules. They really did not get around the rules they just read them very carefully and found a way to get the most out of a transmitter that no one had ever thought of before. By the end of this post you will know why they were approved.
... Let keep this very clear and it has nothing to do with your final stage amplifier that cannot exceed 100mw DC input power.
Ok most the transmitters being made today have the final amplifier and your PI Network all in the same box . Some of the Pi Networks are design to tune your antenna. .... Ok this is not your regular AM part 15 transmitter.
http://www.iamradio.net/range-extender-2.5.htm
This is how the company was able to get around this rule. They broke their transmitter up in to two sections.
First section being Audio stages,PLL synthesizer for your frequency and your final amplifier with no filtering or tuning section. If it had these then you could not run coax to an antenna.
Company was smart put a tuner that acts like you filter as well antenna Matching section in a separate box.
Now you are not running coax to your antenna but now your final filter and tuning section of your transmitter. This is why the filtering section has an antenna coming out of it.
Since the antenna comes out of the filtering section and tuner section the FCC sees no feed line to your antenna.
What they do see is a connection between your final transistor and your filtering section that just happen to have a matching network.
So that coax can be as long as you want because it is not directly hooked up to your antenna but instead to your filtering and antenna network box.
If this transmitter had the feed line coming out of the filtering section and antenna matching network box to your antenna this transmitter would be shut down.
When they design this transmitter they really thought about how to get around the [3 meter] rule.
The FCC could do nothing because it had meet all the current rules of the time this transmitter was being approved . .....
.. At least you know how they were able to get the coax to the filter/tuner section. They do not see the coax coming from the transmitter to the Antenna.
They see the coax coming from the final output transistor to the filter/tuner section. Your antenna comes off the Filter/tuner section box and has no coax between them.
This is the only reason why this transmitter set up was ever approved.
They broke the transmitter up into two separate sections. The coax is not recognized as feed line but instead just a wiring section to connect the entire transmitter together.
Does this now make any sense to everyone.
I hope this is a real help and and clears up why the FCC approved that transmitter setup.
It is very legal by the rules that the FCC had set in place when this transmitter was being approved.
There's always a loophole if you look hard enough.
Yes, I suppose there are always loopholes, but that doesn't answer the question.. which is: From a technical standpoint, does his explanation genuinely illustrate such a loophole?
"..So that coax can be as long as you want because it is not directly hooked up to your antenna but instead to your filtering and antenna network box.."
He implies that from a technical standpoint that the coax essentially does not exist in respect to the 3 meter length limit.. I don't get it, that doesn't make sense to me. But he emphasizes his 40 years of dealing with AM broadcast engendering and first hand associations with the FCC etc, and appears to speak with a degree of conviction regarding how and why the Range Extender is compliant with the rules ..
I lack such technical expertise, so that's why I'm asking if any of what he said is actually valid?
Or does what he said simply not ring true at all?
@richpowers I don't know what you mean by filter. I assume you mean the ATU(antenna tuning unit) and the actual antenna?
So the loophole here is the antenna tuning unit and the antenna is separated from the actual transmitter in two distinct components and housings and since the coax is not a feedline directly to the antenna from the transmitter's final amp peaked for max signal but goes to the second component which contains the ATU which could be considered a "stage", and then the antenna the coax joining the two is not considered a feedline in the technical definition of a feedline.....so I have it right? There is no feedline directly linking the antenna to the final which includes the ATU as that is part of the of the final amp. The two are split up.
I guess if you want to get very technical about it this could have been how it got the certification. The poster is also assuming with an educated guess at how certification got around the feedline issue. He doesn't know for sure that's how it was done. Unless he had direct contact with the manufacturer and the FCC.
Yes in my mind stretching it but a loophole possibly. Here's the thing though. You don't have to have an ATU, you can have an unpeaked output from the final and in that case the talking house range extender with coax would now be a true feedline as it would contain only the antenna. The loophole, the ATU in the separate box with the antenna. So a "stage" before the antenna.
Stretching it, but a possible loophole in my mind.
Technically, I think that the argument that this is legal is crap. It reminds me of the argument regarding ground leads and radiating masts (referencing the KENC controversy).
Talking Sign (i.e., ChezRadio), attempted to get a similar device to the Range Extender approved for use by the Talking Sign transmitter here in Canada, and it was soundly rejected.
@artisan-radio When I talk to Gerry again I should ask about that. But to Rich Powers, really you don't need it. Well, maybe you do need it. The reason the extender works with the Talking house is the built in automatic tuner is not accurate in getting the perfect peak as a youtube video demonstrates this. When you bypass the internal automatic inaccurate ATU for the manually tuned range extender you get a better peak for max gain to the antenna. Plus you get it outside in a better location. But I think the best is like the Procaster and the Rangemaster or the Talking Sign.
With the antenna attached to the transmitter as supposed to be there is no signal loss through a "feedline"
Here's a demo of how innacurate the internal tuner is on the Talkinghouse. Ignore all the audio mods this poster made I just wanted to show the inaccuracy of the tuner and why it works better with the range extender.