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Post by End80 on Apr 21, 2019 5:23:10 GMT
So in the dictionary also as does the NOUOs: "It is interesting to note they seem to use ground lead and ground wire interchangeably".
The "ground lead" is the part of a circuit formed by the earth - regardless if that conducting circuit is a actual wire, a steel tower, or whatever other form of conducting path used. Any conducting material you connect your transmitters antenna system to extends the length of your system.. If the entire antenna system exceeds 3 meters then it does not conform to the rule as written.
But like I said, it never has, and as Legacy points out above, the certified Talking House never really conformed to the rule either... 15.219 is a convoluted rule, and the best you can hope to do is to conform and operate in respect to legality is to either install a few inches above the ground OR insure the intent of the rule which is to maintain your range to under a mile radius.
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w9lwa
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Post by w9lwa on Apr 21, 2019 5:45:19 GMT
www.merriam-webster.com/dictionary/ground%20lead ground lead noun Definition of ground lead 1 : a contrivance for guiding a cable that hauls logs along the ground 2 : ground wire
ground wire noun Definition of ground wire 1 : a wire making a ground connection 2 : the part of a circuit formed by the earth
Well, I think we can agree on those definitions, if nothing else. I'm proposing that it's legal to mount a Rangemaster or similar device atop a tower of some height and attach the ground lug of the Rangemaster to the top of the tower with a short length of wire. By the above definitions, I see nothing to suggest noncompliance: 1. My ground lead is indeed a wire - which I would define as well, a wire. Not a tower, water pipe or rod in the ground. 2. My wire makes a ground connection - between the Rangemaster and the tower it's mounted upon. I suppose the bottom of the tower is grounded since it's stuck in the earth. My wire doesn't make the entire connection, but nothing says it must. (In fact, see number 3 below that it must only be part of the circuit with the earth.) 3. It is part of the circuit formed by the earth - Indeed, not the whole circuit, but that what part means as opposed to making the whole circuit, which it could say easily enough, but does not. You can limit your system if you wish, but I don't think you must. My system is fully compliant pursuant to the above definitions using plain and ordinary language. The significance of that is that laws with criminal penalties must be applied according to their plain and ordinary meanings. I appreciate your comments. John W9LWA Well, I guess there a couple of more things: 1. What is a talking house and how does that fit in to the discussion? 2. What is this apparent exemption for signals that don't go over a mile? Is that some unofficial understanding that the FCC will leave you alone if your signal doesn't go farther than that? Now, that sounds like trouble unless there is a declaratory ruling. I'm sure you'll do as you wish, but I think you're safer with my definition of a legal ground than with any unofficial understanding with someone at the FCC.
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Post by thelegacy on Apr 21, 2019 5:48:03 GMT
I'm going to keep saying the same thing about range and that is there are plenty of sites and even a needs himself told me you can achieve about a mile to a mile and a half sometimes to miles but the average is about a mile to a mile and a half. When I talked about a mile and a half I'm not talkin about a portable radio I'm talking about a car radio because the sensitivity is at 0.9 microvolts.
AM radio is a dying band (money wise) so I say install it so that it physically we'll look like it follows the rules. You're not likely to get in trouble if you're getting out about a mile 2 a mile and a half maybe two miles but I'm talking about in a noise free environment. You really need to look on YouTube there are plenty of users width a 2-mile range and have not gotten a NOUO. Good Luck
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Post by End80 on Apr 21, 2019 5:56:29 GMT
To illustrate the point I keep trying to drive to, download the Savannah NSR Interpretive Radio System case study. It details their part 15 AM system installations. This is basically how it's been done at historical and park areas for ever since Yellowstone first began doing it 50 years ago. This particular system uses Talking Houses with external ATUs. They are elevated 10 feet and well grounded (already exceeding the 3 meter rule) and to boot they extend it even higher with the ATU (which in spite of also being FCC certified doesn't conform to the 3 meters either). But this is acceptable and very well established method anyway.. However, this is basically identical to the historical installations throughout the past half century.. and as always the range is maintained to under a mile for each transmitter.
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Post by End80 on Apr 21, 2019 6:06:28 GMT
Yes.. you can exceed much farther than a mile with a part 15 transmitter (all it takes is a massive extension of the antenna system).. But, historically speaking, it has never been permitted. Longer ground leads have always been permitted (unofficially), but never ranges greater than a mile. Not with Yellowstone, not with Atlantic Records, not with the Sea Grant operations, not with Talking Houses,.. Never has over a mile been permitted in any of the documented or high profile cases. It's never the length of the ground lead that's the true issue, it's always excess range.
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Rich
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Post by Rich on Apr 21, 2019 12:13:31 GMT
Only Physics tells us the radiation characteristics of the components of a transmitter+antenna system for a given hardware configuration and installation environment.
Judges, lawyers and the typical operators of unlicensed AM/FM transmit systems are unlikely to understand how they operate without an accurate knowledge of, and use of Physics.
Note that even the most basic definition of a "ground lead" and/or "ground wire" applicable to electrical and electronic systems requires at least one end of it to be connected to the potential of true, literal ground. A true ground does not, and cannot radiate e-m energy.
And as posted and illustrated earlier in this thread, a true ground at radio frequencies does not exist at the top of any/every elevated, conducting path whose opposite end is connected to true r-f ground.
Rather, Physics shows that such paths are a radiating part of the antenna system.
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w9lwa
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Post by w9lwa on Apr 21, 2019 17:58:58 GMT
Well, I don't know about that, Rich. It may be physicists who understand the science but it's not the laws of physics that are enforced by federal courts. It's politicians who are responsible for laws and regulations and Judges who ultimately enforce them or not - whether or not they actually understand the issues at hand. It's not unlike global warming. Politicians and Judges can take the science into account or not as they see fit.
You can't make this too complicated for non-scientists to understand if they are breaking the law or not. Laws with criminal penalties don't work that way. Otherwise, federal prisons would be full of twelve year olds who received transmitters for Christmas but didn't consult with physicists before grounding their antennas. Perhaps those of you who disagree should ask for a declaratory ruling that 47 CFR by implication incorporates the laws of physics. That would be the only way they would have any real impact here. That's just how it is in the real world of law and politics.
I appreciate your comments.
John W9LWA
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Rich
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Post by Rich on Apr 21, 2019 19:00:42 GMT
...You can't make this too complicated for non-scientists to understand if they are breaking the law or not. ... But neither should this be made so simple that non-scientific operators of unlicensed AM/FM systems fail to understand what may lead the FCC to issue them an NOUO, or worse.
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w9lwa
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Post by w9lwa on Apr 21, 2019 19:17:26 GMT
...You can't make this too complicated for non-scientists to understand if they are breaking the law or not. ... But neither should this be made so simple that non-scientific operators of unlicensed AM/FM systems fail to understand what may lead the FCC to issue them an NOUO, or worse. Could be. I think the average person thinks a ground lead is one of those copper web straps they sell at Pep Boys. If the regs indeed comprehend that a ground lead includes any metal between the transmitting system and the earth or whatever it is, they could just go ahead and include it in the regulatory language. I suppose that would clear it up? Thank you for your comments. John W9LWA
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Rich
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Post by Rich on Apr 21, 2019 21:28:53 GMT
...Thank you for your comments. And I thank you for yours, John.
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w9lwa
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Post by w9lwa on May 2, 2019 6:05:59 GMT
Does anyone have an opinion regarding use of an Isotron antenna that supposedly needs no ground? I'm seeing a lot more bad than good about these things these days and in addition to the ground issue, I'm wondering if anyone has actually obtained good results in a Part 15 AM setup?
All comments much appreciated.
John W9LWA
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Post by Boomer on May 5, 2019 13:27:28 GMT
At one time I'd studied the Isotron, it's certainly a novel looking antenna, with space age design. In my time reading Part-15 pages, I haven't seen anyone who has tried the Isotron and reported on it on the groups. One reason might be that since the Isotron already has its own loading coil component, it's designed for low impedance input, 50 ohms, where most of the transmitters used by Part-15 operators already have loading coils and high impedance outputs to feed their own whip antenna or wire directly. That cuts out a good portion of potential users.
I saw one video a few years ago, a put one on a pole in his back yard, and walked around his whole town hearing the signal, but he was experimenting by running a few watts into the antenna, not milliwatts. He was freaking out, carrying a portable radio and walking the trails around his local lake, and the signal was still good. If I find the video again, I'll post the link for it.
From reports, the Isotron is considered a whip antenna and a loading coil between two plates of a capacitor, which are its end brackets. That's probably why they can claim it doesn't need to be tuned after you get it, as the structure is built with controlled properties. A benefit might be the larger external loading coil, where most transmitters have their smaller loading coils inside of the case. That could mean a higher Q-factor for a stronger resonant peak.
The problem with any short antenna though is the 'aperature size', based on the length of the radiator. A standard quarterwave antenna like a licensed broadcaster would use is around 150 feet long near the top of the AM band. Part-15 antennas are ten feet long, and make up for the lack of length by using the loading coil. There's just not a lot of surface to radiate a signal from with a ten foot antenna, which is the real limitation we're dealing with.
Boomer
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Post by Boomer on May 6, 2019 1:53:20 GMT
I like this site and explanation of short antenna matching on the AM broadcast band. The author builds with vacuum tubes, but the same principals would apply to transistors, matching and the circuit path the signal takes. electronbunker.ca/eb/AntennaMatch.htmlBoomer
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