GENERAL NOTES FOR EXPERIENCED QRP BUILDERS:

We at Ramsey Electronics deliberately designed the HR-series of DC receivers to be easily available, affordable and buildable by any person willing to follow the assembly directions. To achieve this goal, the current models, with direct coupling of the SA602 to the LM386 operating with a gain figure of 50, use an amazing minimum of parts. If you know what you are doing with DC receiver design, we encourage you to use our HR-series for reliable building blocks for achieving maximum performance for you own application. If a good idea does not work as expected, you can easily restore your Ramsey receiver to its original circuit configuration.

Our job has been to keep in stock for immediate delivery a good basic design, a quality PC board with plenty of work room, useful front panel controls, correct and adjustable inductors, workable varactor tuning and the popular SA602. We know these receivers WORK, as specified, and that the ONLY reason any HR-receiver will not work after the 1-2 hours needed for assembly is if we packed the wrong parts or you put them in wrong. Once you are sure the receiver performs as specified, there is a lot you can do to coax maximum performance from the basic circuit.

For instance, if you choose a DC power source other than the 9-volt battery, the space allowed for the battery offers plenty of room for a top mounted perfboard or PC-board for preamp stages and or any sort of passive or active audio filter that suits your needs. Keep your work neat with short leads so as not to introduce broadcast station overload.

ALTERNATE POWER SOURCES:

Most of the HR40 circuitry can be operated from 6 to 14 volts without damage or significant modification. However, it is quite important that you carefully hook up with the correct polarity; reverse polarity or excessive voltages WILL damage your kit.

BANDSPREAD AND TUNING RANGE:

The easiest way to enjoy finer tuning , if you plan to use your receiver only for checking your favorite segment of the band, is to adjust the oscillator coil so that your desired segment falls within the second half of the rotation range of the tuning control. The first half of the rotation range covers about 70% of the actual tuning in KHz, while the other 30% is spread over the other half of the rotation range. If your interest is in monitoring SSB, the normal alignment will work fine. For optimum CW only listening, set the lower band edge with the tuning control in the 12:00 position of its range.

HR40 • 20

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Ramsey Electronics HR40 General Notes for Experienced QRP Builders, Alternate Power Sources, Bandspread and Tuning Range
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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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