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Here is the FCC rule:
Section 15.219 Operation in the band 510 - 1705 kHz.
(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.
(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.
The following statement from the FCC DC enforcement office is intended to clear up any confusion about 15.219(b):
The 3-meter combined length specified in Section 15.219(b) refers to the length of all radiating elements. Attaching the ground lead to an unshielded radiating object, or the addition of a ground screen, will cause the effective length of radiating elements to exceed 3 meters, in violation of Section 15.219(b).
Please do not disconnect a safety ground from any device including ours, no matter what you read on the internet. (Varied claims about grounding, or "certain" heights at which transmitters "have" to be located. If you feel you have a ground radiation issue you want to deal with it in a practical way, disconnecting the safety protection system is not recommended, disconnecting these recommended protection systems can lead to injury and personal harm. (lighting related damage and fire).
See how the typical indoor AM Part 15 is grounded, there are probably a million of these in use.
We have found with customers that install elevated grounds or ground wires that are obviously intended to radiate, most of the time an FCC agent will ask that they be removed. If the transmitter is installed over an existing metal object like a metal roof sometimes they may be allowed. There is typically no problem with adding radial wires in the dirt ground to improve the electrical connection with the earth. The inspecting agent has the authority to approve or disapprove a particular system. As always follow FCC law and fully cooperate with the FCC.
See these other pages:
We recommend following FCC law and fully cooperating with the FCC. If you have any issues with an FCC inspection we will help sort things out and work with the inspecting agent to get you into compliance.
With regards to the installation, the main issue for the user is to make sure he/she complies with section (b), which specifies the antenna configuration. The primary point here is to make sure the total length of the antenna wire, the ground wire, and the transmission line from the device to the antenna (if used) does not exceed 3 meters.
The intent of the regulation is to limit the physical size of the antenna system such that the radiated field strength does not create interference with licensed AM stations. This product does not use a transmission line, so we are only concerned about the total length of antenna and ground. The antenna length is obvious and easily measured, but the ground is not as clear cut. How do you limit your Antenna system to 3 meters? A solution for this is to install a ferrite choke core or other filter in the ground wire coming from the unit. This choke has a very high impedance in the AM broadcast band, and essentially reduces the currents on the outer portion of those conductors to zero. They are now not a part of the antenna system.
We Stock two types of Filters, the AM1000FER and the AM1000FIL. The AM1000FER is inexpensive, plans to build it follow. Though a gas tube can be added to the Am1000FER to add some level of lighting protection the level of protection still is not great.
The AM1000FIL however has better lighting protection performance, this filter can be purchased from us, please call to purchase.
Choke coil details (AM1000FER)
Do not use fewer turns then recommended. The choke coil should be installed directly at the ground terminal binding post of the transmitter to limit the radiator in the system to the approved length limit.
Place a gas tube such as the Bourns 2027-23-BLF 230 Volt in parallel with the Choke coil to improve lighting protection performance as the choke coil by itself does severely degrade the lighting protection performance of the transmitter.
You can request the "Ferrite Choke AM1000FER" filter along with your order for an additional $50, or the AM1000FIL for $15.
This Ferrite choke AM1000FER is slow to respond to lightning and does affect tuning,
Ferrite Choke filter AM1000FER pictured , gas tube not shown
You can also place a 1-5K carbon resistor in series with your ground wire, bypassed with a gas tube. This is the AM1000FIL.
These parts can be bought
Resistor 588-OA102KE (May be out of stock)
Resistor is 1Watt 1K carbon resistor
A good way to test your ground system, to see if it is radiating ( you will need some sort of field strength indicator) is to check the field strength, then remove the ground, retune, then check the field strength again. If you show significantly more field strength with the ground connected then your ground is radiating.
Avoiding a radiating ground
If you are connected to a ground that looks like an antenna , then you are going to get radiation from the ground system. Design the ground so that will not radiate, or does not function as an antenna. For example a pole grounded at the base with a short "ground lead" connected from the top of the pole to the transmitter has been shown to be a solution.
Tower mounted and billboard mounted transmitters are notorious "ground radiators"
But not all grounds radiate, really the only way to tell for sure if your ground is radiating is to perform the test mentioned above.
A suggestion would be to do the best you can to be sure your ground system is not a radiator but keep a ground filter to install later in case an FCC agent comes by & feels your ground system is radiating.