In fact, the most significant distance in the above chart is the 1.9 µV signal strength permissible at 1260 feet (about 1/4 mile), covering a circular area of about 114 acres. A quick glance at stereo FM receiver specifications shows typical sensitivity of 1.7 µV before considering high-gain antennas or preamplifiers. Your non-licensed signal can provide serious competition to a public broadcast station fifty miles away, a station which someone in your neighborhood may have set up a special antenna to enjoy.

Calibrated "field strength meters" such as described in the ARRL Radio Amateur's Handbook can detect signals down to about 100 microvolts. To measure RF field strength below such a level, professional or laboratory equipment and sensitive receivers are required. A "sensitive" receiver responds to a signal of 1 or even .5 microvolt "delivered" to the receiver input by antenna. If the antenna is not good, the receiver cannot respond to the presence of fractions of a microvolt of RF energy.

SUMMARY

The present edition of Part 15 of the FCC rules does not provide detailed guidance on ALL aspects of using a low-power transmitter such as the FM10A. The main point is that you may not cause any interference whatsoever to licensed broadcast services and that you must be willing to put up with any interference that you may experience.

In addition to operations not requiring authorization, you also have the option of writing a clear and polite letter to the FCC Engineer-in-Charge of your local district, describing your intended operation. Mention the operating frequency and planned hours of operation. This could be a good step to take if your project is on behalf of a school, Scout or community group.

If you become further fascinated with the service rendered by low-power broadcasting, other FCC regulations explain how to apply for a license or other authorization which may permit you to upgrade your FM10A or other equipment to accomplish any objective which the FCC sees to be in the public interest and not interfering with other authorized uses of the radio spectrum.

Lawful use suggestions for the FM10A

1.Build and adjust this kit strictly according to the published instructions.

2.Use the whip antenna supplied with the Ramsey case set, CFM.

3.Do not modify your kit in any way.

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Ramsey Electronics manual Summary, Lawful use suggestions for the FM10A
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FM10A specifications

The Ramsey Electronics FM10A is a compact and efficient FM transmitter tailored for hobbyists, educators, and anyone with a passion for creating their own radio broadcast. This device stands out in the world of electronics due to its user-friendly design and array of features that make it an ideal starting point for both beginners and experienced users.

One of the main characteristics of the FM10A is its simplicity in setup and operation. Users can quickly assemble the kit without the need for advanced soldering skills, making it accessible to a broader audience. The transmitter operates in the FM band, allowing for high-quality broadcasts with minimal distortion. Its frequency stability is maintained through a PLL (Phase-Locked Loop) technology, ensuring that the transmitted frequency remains consistent throughout its operation.

The FM10A features adjustable transmission power, allowing users to customize their broadcast range. With a maximum range of approximately one mile under optimal conditions, this device is versatile enough for personal use, small events, or classroom demonstrations. Additionally, the transmitter is equipped with an audio input for connecting various media sources such as smartphones, computers, or other audio devices. This flexibility makes it suitable for a range of applications, from playing music to broadcasting educational content.

Another notable feature is its compact design, which makes the FM10A easy to transport and set up in different locations. The device is powered by a standard 12V supply, which is widely available, making it convenient for users at home or on the go. The lightweight nature of the unit further enhances its portability, enabling users to take their radio broadcasts anywhere.

The FM10A also includes an LED power indicator and a built-in antenna for straightforward operation. Users can enhance their transmitting range by adding an external antenna, providing further customization based on specific needs. The kit comes with comprehensive instructions to guide even those new to radio transmission through each step of assembly and operation.

In addition to its engaging technical features, the FM10A serves as an educational tool. Users can learn about radio frequency technology, electromagnetic theories, and audio broadcasting principles, making it an excellent addition to any STEM program. Overall, the Ramsey Electronics FM10A is a stand-out choice for anyone looking to delve into the world of FM transmission with a robust, user-friendly device that doesn't compromise on quality and functionality.
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