It's possible to get over a mile range with a ground-mounted and legal installation (that is, 100mw or under, and antenna + ground wire <= 10 feet. I've done it, others here have as well.
I really have no sympathy for those that violate the rules knowingly, regardless of the reasoning. Whether that is the case here remains to be seen.
As pointed out all installation situations are different. I have no tolerance for Ham cops.
I'm not sure what you're saying, John.
Do you condone obvious long ground wires? Or running over legal Part 15 power? What gives them the right to do that when most others struggle along within the rules? And it's those guys the FCC points to when they give their reasons for not easing the rules.
Part 15'ers have to show that they can be good corporate citizens before the FCC (or Industry Canada) will even think about changing the way things are now.
I personally would never report someone (although I understand why there are those that would - they are, after all, breaking the law), but certainly don't waste sympathy on anyone who is caught with their pants down, so to speak.
He is saying that installation circumstances are different for everybody. Not everyone has the luxury of mounting a transmitter on the ground.
From the AM1000 manual:
How many ground mounted transmitters do you see here?
Where in the instructions, does it say place the transmitter on the ground?
But that's not the issue. Even if it's difficult or impossible to install a Part 15 transmitter on the ground, that's no excuse for breaking the rules. In my opinion, at any rate.
Anyway, this has been beaten to death and it's probably time to move on.
You stated: "Why is it so difficult to stay at 100mw with a ground mounted install?"
I am just trying to show you that it is difficult, depending on individual circumstances.
Every pictured transmitter included in my previous post was probably installed under the assumtion that they are legal installs, per the instruction manual for the AM1000.
No one is condoning purposely breaking the law. Different circumstances lead to different types of installs.
You're right, it's time to move on to the next FCC issued NOUO, and the next could be issued to you...ground mounting and all. (Alright, maybe not you, if you are in Canada...)
Many times, the violations seem to be a matter of what the inspectors feel their personal interpretation is of the rules at the time of the inspection. That is not fair, and the rules interpretations should be standardized. That's the issue.
For comparison, a fully legal ground mounted antenna with 16 10ft radials over 8mS/m ground conductivity, out in the open and clear of obstructions will produce a field strength of about 5,968 uV/m at a distance of 40.7m, well below the measured 30,000 uV/m.
A ground mounted antenna, out in the open, would yield a range of 4,415ft for the standard "fringe" signal level of 150 uV/m, and a range of 1 mile (5,280ft) at the slightly lower field strength of 121 uV/m.
So car-radio range of 1 mile can be expected for a good ground mounted antenna clear of obstructions. The location of the NOUO installation clearly shows major obstructions, so his range would be a lot less. All those closely spaced 2 story buildings with their wiring and plumbing and heating pipes would surround a ground-mounted antenna with major shielding.
The location of the NOUO installation clearly shows major obstructions, so his range would be a lot less. All those closely spaced 2 story buildings with their wiring and plumbing and heating pipes would surround a ground-mounted antenna with major shielding.
From e-m theory and from widespread experience -- are the groundwaves of MW transmit antennas significantly affected by 2 story residential buildings with their contents of wiring/plumbing/heating pipes that are located in the far fields of such transmit systems?
As far as I know, there is no constitutional right to install a Part 15 transmitter and get a good signal regardless of where you live. You still have to live within the rules.
Those rules are - 100mw input to the final stage, and an antenna + ground wire maximum 10 feet in length.
If you violate those rules, then you run the risk of getting an NOUO. It's obvious that this station's elevated installion has a long ground wire, which, as some have pointed out quite eloquently, gives you a much greater signal than a ground mounted installation with a legal antenna + ground. There seems to be no personal rule interpretation from the FCC inspector here - it's black and white.
It's your right to disagree with the rules. But until they're changed, I believe that you should attempt to stay within them.
If you don't like the antenna and power limits, you can also operate under Part 15.209.
Of course radiated field strength must meet guidelines of that rule but you can quit worrying about your antenna system.
Rich, how much TPO could be applied to a 1/4 wavelength vertical and stay within Part 15.209 guidelines? It would be interesting to compare patterns of a 3 meter antenna to a 1/4 wave antenna both meeting the field strength requirement.
And then of course there's always the carrier current station which has shown promise in some applications.
There isn't much information easily available on the web regarding "obstructions" in the reactive near field of an antenna, so I am only offering a possible explanation for the known poor performance of a ground mounted 3 meter antenna surrounded on all sides by buildings. This explanation also may account for the known poor performance of an antenna mounted within a few inches of a building wall over the entire antenna length, and the known poor performance of indoor antennas.
At 1600 kHz, the reactive near field extends out to 97 ft. from an antenna. That's calculated by dividing the wavelength (615 ft.) by 2 x pi. From Wikipedia: "In this reactive region,... there is a "reactive" component to the electromagnetic field, meaning that the nature of the field around the antenna is sensitive to, and reacts to, EM absorption in this region (this is not true for absorption far from the antenna, which has no effect on the transmitter or antenna near-field)." Any perfect conductors in the reactive near field will not rob any energy from the antenna. They will just change the antenna impedance. However, any LOSSY conductors coupled either inductively or capacitively, or both, will rob energy from the antenna. Wiring and plumbing will be lossy at 1600 kHz, so the net energy produced by the antenna and its reactively coupled obstructions will be reduced. In other words, the transmitting range will be reduced.
It's pretty clear to me from the pictures posted that a ground mounted antenna could only be placed in that little patch of ground to the left of the building. The distance to the building would only be about 10 or 15 ft. I judge the other surrounding buildings to be within the 97 ft. reactive near field.
I think the lack of easily available information on this subject is probably due to lack of interest on the part of commercial antenna designers. They just assume that nobody would ever even consider building a quarter wave antenna tower immediately adjacent to, or even inside a 154 ft. tall building!
how much TPO could be applied to a 1/4 wavelength vertical and stay within Part 15.209 guidelines? It would be interesting to compare patterns of a 3 meter antenna to a 1/4 wave antenna both meeting the field strength requirement.
This is shown in the graphic below.
Even though a 3-meter vertical, 1700 kHz monopole antenna system has an electrical height of only 0.017 wavelengths, the shape of its relative field pattern is very similar to that of a 1700 kHz 1/4-wave monopole.
The reason for the difference in the radiation efficiency of these two systems is related to the ratio of their radiation resistance to the resistance of the r-f ground connection; 2 ohms in this case.
(A power of 1.9 nW = 0.000 000 001 900 watts.)
What I was curious about, with all the banter about short antennas being obstructed by power robbing items in the near field, was whether or not holes in the pattern would be less of a problem when using a 1/4 wave radiator producing the same, legal, field strength per Part 15.209.
Logically, producing the same field strength at the same distance one would think the same coverage area would result. The difference I was considering was less holes in the pattern simply due to the phycial height of the 1/4 wave antenna reaching above the obstructions.
From reply #43... I was curious about whether or not holes in the pattern would be less of a problem when using a 1/4 wave radiator ... due to the physical height of the 1/4 wave antenna reaching above the obstructions.
This benefit is much more pronounced in the r-f spectrum above 30 MHz, where propagation uses the space wave along a line-of-sight path.
The wiring/ductwork/metal pipes in residential buildings of 2-3 floors have very localized effects on the propagation of radio waves in the AM broadcast band, only within a few feet of them typically. Their physical lengths in the vertical plane are only a small fraction of a wavelength in the AM BC band, and they don't couple much energy from an arriving radio wave of such wavelengths.
Below is a re-post of a paper I put together on this topic a year or so ago.
You are talking outside the box, MRAM 1500.
You may need to make multiple tries to register with conventional minds who are unaccustomed to considering novel and original solutions.
The status quo might need to be re-arranged.