A better operating arrangement will consist of a T-R switch, either a manual switch or break-in delay relay circuit. This switching circuit can disconnect the SA602 audio output at the volume control, and switch in a pleasant oscillator pitch (keying sidetone) which is amplified to listening level by LM386. The Ramsey Electronics Universal timer kit No. UT-5 is easily adapted as a sidetone oscillator.

•SPEAKER OPERATION

A fifty cent, two inch diameter speaker, lying naked on your workbench will give you a fair test of the speaker output capability. Speaker quality and well- designed enclosures have their clear purposes! A reasonable speaker in a box delivers a pleasant listening volume. On the other hand, the LM386 indeed can deliver more audio output punch than is developed in our HR- series kits. For example, our FM receivers, using the same LM386 audio IC, deliver more volume. These receivers, however, take advantage of IF amplifiers, drift-compensation and crystal controlled oscillators built into mass production, sophisticated FM receiver ICs. A heavier drain on the HR40’s battery by stronger audio will quickly result in chirpy signals and oscillator drift as well as the need for frequent battery replacement. Remember the SA602 circuits similar to Ramsey’s generally call for sets of C or D cell batteries! For Experienced Builders more information regarding audio output is in the general notes.

The simple design of the audio stage of the Ramsey HR40 receiver assumes preference for headphone or small speaker operation, low battery drain and general economy.

•MORE AUDIO POWER - ANOTHER WAY

If you want to use your HR40 for casual band monitoring while you are busy across the room, in the shop, or to share with a class or club, and want LOTS more volume, try building up our very inexpensive Ramsey BN-9, 2 watt general purpose amplifier kit. Supply DC voltage to such an amplifier separately, using D-cells, a lantern or auto battery, or a well filtered power supply.

•ADDING AN LED POWER ON INDICATOR

For many people, a pilot lamp to indicate “power on” is more than a nice touch. They expect it and depend on it , reminding us that “real radios glow in the dark!”

Adding a simple LED power-on indicator to your Ramsey HR40 is easy. All you need is the LED itself and a small 1K or 2.2K resistor. Study the PC traces between the positive battery supply wire and the on-off switch. The unused connectors on top of your switch are an ideal point to get the + DC voltage needed for the anode (longer lead) of the LED. Plan where and how

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Ramsey Electronics HR40 manual Speaker Operation, More Audio Power Another WAY, Adding AN LED Power on Indicator
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HR40 specifications

The Ramsey Electronics HR40 is a versatile and high-performance FM transmitter that has gained recognition among hobbyists and professionals looking to broadcast audio signals. With its robust features and user-friendly design, the HR40 stands as an excellent choice for a range of applications, from low-power broadcasting to personal audio projects.

One of the standout features of the HR40 is its frequency range, typically allowing for transmission on the FM band from 88 to 108 MHz. This broad range ensures compatibility with a variety of receivers and allows users to select an optimal frequency for their needs, minimizing potential interference. The transmitter is designed to offer excellent audio fidelity, with a frequency response that meets and exceeds industry standards, ensuring clear and crisp sound quality.

The HR40 utilizes advanced modulation techniques, which contribute to its performance in terms of signal clarity and range. The use of frequency modulation allows the HR40 to transmit audio signals with minimal distortion, even at higher volume levels. Additionally, the transmitter is equipped with a built-in audio preamplifier, which enhances audio quality by providing a clean and powerful signal before transmission.

Another notable characteristic of the HR40 is its adjustable output power. Users can modify the power level to suit their specific broadcasting needs, whether for indoor use or outdoor applications. This flexibility is particularly useful in managing transmission range, allowing users to tailor their setup without excessive overkill or underperformance.

The compact design of the HR40 also stands out, making it a popular choice for those who need a portable broadcasting solution. The unit is lightweight and easy to transport, while its durable construction ensures longevity and resilience in various environments.

In terms of ease of use, the Ramsey Electronics HR40 offers simple installation and operation. It comes with a clear instruction manual, allowing users to set up their transmitters quickly. The intuitive interface and minimal setup requirements enable beginners to jump right in, while advanced users can take advantage of its expandability and customization options.

Overall, the Ramsey Electronics HR40 combines user-friendliness with a range of powerful features aimed at both amateur and experienced broadcasters. Its excellent audio quality, adjustable output power, and compact design make it a favorite for many seeking reliable FM transmission capabilities.
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