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It has been generally established that wires and metal rods running at or below the surface of the earth are not included in the standard 15.219 3-meter measurement of antenna, ground-lead and transmission-line. This is because such wires/rods are not expected to radiate.
It has been claimed that wires above the earth-surface always radiate, whereas those below that surface do not.
These assumptions place the ground and air into two separate domains.
Of course the surface of the earth can be raised, let’s say by dumping truck-loads of imported dirt over an area, thus raising the antenna rising vertically above that area without increasing the length of any ground-lead between the antenna and the earth.
However, as Mark Twain said (paraphrasing):
“No generalization is completely true, not even this one.”
So far I have stated the subject open for discussion in this thread, namely the earth-ground itself: what constitutes it and how it may be manipulated.
I think you at one time had suggested something like sticking a long PVC pipe vertically in the ground and filling it with dirt with the lead running through it.. ! Technically I suppose a 40 foot high dirt filled PVC pipe could then allow a grounded 3 meter install to be elevated!
Something that has occurred to me since the inverted 3 meter install discussion I had with R Fry on the forum formerly known as ALPB, is that a pole mounted elevated transmitter grounded at the top of that pole would not perform well because of the “high inductive reactance it would take to resonate it”.. This seems to help confirm what Hamilton has expressed many times that many such installations have been passed by FCC field agents. Yet technically it doesn’t appear to meet the 3 meters.
But in actuality, with part 15, technicalities have seldom been the true governing factor behind what determined continued operation of any part 15 transmitter installation. The true governing factor is maintaining the actual intention of the rules – which of course is to limit the range. Outdoor Part 15 transmitters which are elevated and well grounded is the standard and well established method of install. Ground mounts are something new.
It is the only consistent factor for the last 50 years concerning the actual implementation and acceptance of part 15 AM operation has not been the 3 meters, but the range it achieves. There’s no question that leniency has always been evident concerning the 3 meters. That leniency is what got part 15 AM of the ground and enabled it’s rise and continued as a useful medium.
Keep the range limited, that should be a part 15 broadcasters primary concern.. because that is the FCCs primary concern. A mile appears to be about the maximum accepted.
This is my observed conclusions based on the last half century of it’s established common and accepted utilization. I consider this to be more than just opinion.. But feel free to call it that.
Yes And…
End80 Advises: “Keep the range limited, that should be a part 15 broadcasters primary concern.”
Absolutely, and I guess that the concern by the FCC about range is a balance between leniency for the low power operator and the interest of licensed broadcasters who reasonably do not want unlicensed services to compete with them.
I would add a second primary concern which is obvious: keep all interference below the minimums set in 15.209, which we realize is the whole intent of the part 15 rules in general.
Which brings us to my favorite riddle: “Part 15 Intentional Radiators may not cause interference and must accept any interference.”
At first blush that guideline might seem to take away the individual rights of a citizen to complain to the FCC about interference on the radio dial, but here’s what is being said…
Any interference experienced by an individual which affects his radio listening experience can justly be submitted to the FCC as a legitimate complaint.
Any interference experienced by an Intentional Radiating Device must be accepted because the device does not have the same rights as an individual person.
All I can say is I’ve read what Keith from Rangemaster said 1-2 miles. Its also what the FCC agents told me when they visited me. They could not understand Why FM past the rules when legit AM part 15 would get me to that Deltaville market 1 and a quarter mile away (Less than 2) and Taylor’s which is the same distance the other direction. Stingray Point Marina is 2 miles.
With that and my Broadcast Engineer’s help I feel that there should be no issues with a 2 mile coverage with a decent Radio not a Wall Mart special, Emerson, or Radio that requires a 2 microvolt signal just to barely come in on a junk Radio.
There is realistic Range and pipe dream Range. I don’t expect to be heard on a clock Radio 2 miles away. You would be lucky kat 1/4 mile and that is pushing it.
Oh and a Tecsun, Grundig, Sangean, Carver, Macintosh, Sony Elite is what is known as High End Radios that should bring reception.
All I’m saying is that historically (1968 to 2019) the commonly acceptable range of 15.219 has consistently been under a mile.
I’ve never come across a single indication found in any published documentation in the last 50 years, such as those found in magazine or newspaper articles, natural and state park documentation, highway department documentation (when they were still predominately using part 15), minutes transcribed from official meetings, or for that matter in any technical calculations that 15.219 achieved greater distances than about a mile. The same goes for past and present providers of TIS companies which also provide the unlicensed part 15 option installations – The range is and always has been generally under a mile, more often than not actually half that… and most commonly that is in reference to reception to a car radio.
I realize there are plenty of part 15 hobbyist achieving more than a mile, but historically that is unheard of. Part 15 is by it’s very definition a limited range medium. If hobbyist could just keep that fact in their heads then I doubt any will ever run into problems like many others have in the past.
Greater ranges can be achieved with extra effort and expense by employing numerous transmitters (for example like Radio Sausalito has been doing for the last 20 years).
Or.. you can disregard the established historic use as flawed and follow your own path.
I think the key difference here is that a licensed station has precedence and rights above that of an unlicensed intentional radiator.
TIB
RE: I’ve never come across a single indication found in any published documentation … or for that matter in any technical calculations that 15.219 achieved greater distances than about a mile.
NEC4.2 shows that a 3m Base-driven Whip+Tx @ 10m AGL, 10m Lead from Tx to Ground Rod, 100 mW d-c input to Final RF Amplifier, 65 mW PA RF Output Power, 15 ohm Loading Coil, 8-m Buried Ground Rod, and 5 mS/m Earth conductivity produces a groundwave field at 1650 kHz ranging from about 0.6 millivolts/m at a horizontal distance of 500 meters to 0.1 millivolts/m at 3220 meters (about 2 miles).
A field of about 0.1 millivolts/meter can be useful to a good AM receiver in a low noise, low-interference receive location.
However this installation is similar to some unlicensed systems producing NOUOs for some operators.
I’m inclined to side with RichPowers on this one. 2 miles is unrealistic, unless you’re dealing with a car radio (and even then it’s pretty unlikely), or are getting a signal induced into power lines (and you’re close to those power lines).
My experience with multiple transmitters is that I got about a mile, maybe a bit more, as the crow flies, to a car radio, in less built up directions. The signal was weak, but listenable, at least to my ears. With my Rangemaster, I was able to receive the signal up to slightly less than 2 miles away in one direction only, and I believe it was due to one of those exceptional circumstances (and it was only in one, localized area).
The NEC simulation that Rich quotes should be viewed as a best case scenario, as it doesn’t take into consideration the myriad of factors that can degrade an AM signal, including geography, background noise, interfering obstructions, weather, etc.
If I was to generalize with my 13 years of experimentation, I’d say that you should count on 1/4 to 1/2 mile reasonable signal in most areas (more in less noisy, rural areas), and up to a mile with weak signals (again, more in rural areas). That’s with a car radio.
Where I used to live on Bowen Island (essentially a rock sticking out of the ocean, so very poor ground conductivity), the best I could do to a car radio was about 1/4 mile with the same transmitters.
Basically, it all depends where you live, and what you’re using to listen.
Puzzler
Just earlier, in Post pm #110451, Rich demonstrates with NEC4.2 that a legally compliant part 15 installation under 15.219 can and has been subjected to an NOUO from the FCC.
What are we being told?
For one thing Rich shows that 2-miles can be reached after all, overshadowing earlier estimates that 1-mile is the best expected. That could come as hopeful news for operators hoping to gain every inch of legal range.
But hold on. In the same presentation is a risk assessment pointing out a history of stations in this legal category being denied their right to operate by a bring-down notice from the FCC.
One gets the immediate feeling there’s more to the story, but we also know that NOUOs don’t give all the facts about what’s behind them, and Rich hasn’t shared any insight from his point of view as to why legal operators would be treated the same as pirates.
Therefore, for all of Rich’s claim of truth and accuracy his post earns the mark of incomplete.
An abundantly-confident Carl Blare wrote (in part): … Rich hasn’t shared any insight from his point of view as to why legal operators would be treated the same as pirates. … Therefore, for all of Rich’s claim of truth and accuracy his post earns the mark of incomplete.
The description of my “Part 15” setup included this: 3m Base-driven Whip+Tx @ 10m AGL, 10m Lead from Tx to Ground Rod, (etc).
>>That setup is NOT a legal system permitted by FCC §15.219.<<
Carl Blare earns marks of “F” for his comprehension and fact-checking.
Grade Book Adjusted Accordingly
Rich’s grade has been switched to a “complete” for having described a non-compliant setup being served with an NOUO from the FCC.
Basically, it all depends where you live, and what you’re using to listen.
That about sums it up, location and it’s surroundings makes a major difference upon range for part 15, as does the receiving radio itself.
I do suspect however that a completely legal install could feasibly achieve over a mile radius providing the conditions (terrain, ground conductivity, ect.) are optimal.
RE: … a completely legal install could feasibly achieve over a mile radius providing the conditions (terrain, ground conductivity, ect.) are optimal.
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Possibly. But other things equal, not with the coverage radius and reliability of an illegal installation such as the transmitter+3-meter whip installed on the top of a tall mast, and using a long, radiating conductor connecting the transmitter ground connector to a buried ground rod.
Possibly. But other things equal, not with the coverage radius and reliability of an illegal installation..
Well we weren’t talking in reference to an illegal install, but it’s good to hear your conformation that it is plausible that over a mile can be legally achieved.
Out of curiosity do you also agree that an legal elevated grounded install could be achieved by modification of the existing terrain as in Carle scenario of using dump trucks to create a kind of mountain of elevated earth (an extreme due to expense), or as described in another post, actually building a structure (like the mud hut) made of earth and running a ground through it’s walls with the transmitter on it’s roof… Both ideas ridiculous perhaps, but technically seems it would be legal.
Or as also described above; a PVC pipe sticking 10 foot out of the ground filled with earth and the lead running through it to the ground rod.. wonder how that would play out as far as the 3 meters
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