hearing about significant performance improvements, we do not recommend casual modification attempts.

However, there is one practical customization which could be undertaken by experienced VHF experimenters who wish to take advantage of the NE602's ability to accept a crystal resonator instead of the existing L-C tank circuit. The goal would be a one channel repeater monitor or dedicated packet receiver. Inductor L3 and associated capacitors would be replaced by the appropriate crystal tank components. Remember that the crystal oscillator should be planned to operate 10.7 MHz. above the desired receiving frequency. Please do not attempt such a project unless you have a clear knowledge of oscillator design and have reviewed and understood the terms of your Ramsey Kit Warranty. We regret that the factory cannot offer any assistance in performing this or any other modification, so... you're on your own, but that's what experimenting is all about!

A helpful article on the Signetics NE602 IC, including a discussion of crystal- controlled oscillator configurations, was written by Michael A. Covington with acknowledged assistance from Signetics personnel, published with good circuit illustrations in Radio-Electronics magazine for April 1990 (Vol 61, No 4). This will help you understand your SA602.

A less complex approach to the same general goal, eliminating the expense of a crystal and the logistics of adding it to the PC board, is to "undo" the excellent tuning range we designed into your receiver! This would require selecting appropriate values for C9,C10 and C12 and reducing the effect of the varactor tuning to perhaps a 100 KHz swing for fine tuning purposes only. Try reducing C12 to 1 or 2 pF for starters.

Finally, the only pin of the MC3359 not used in our circuit is pin 15, for scan control. Perhaps you will come up with some fascinating idea for it!

Again, please be sure that you understand your warranty, and that you understand your receiver and how to keep it working, before attempting any modifications.

If you've enjoyed this kit, be sure to check out the entire Ramsey kit line. We have a whole series of nifty synthesized VHF FM Transceiver kits that not only teach state-of-the-art technology, but are fun and easy to build, too! Call or write for our catalog.

FR146 • 22

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Ramsey Electronics FR146 manual
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FR146 specifications

The Ramsey Electronics FR146 is a versatile RF transmitter that has gained popularity among hobbyists and professionals alike for its reliability and performance. This compact and efficient device operates in the 146 MHz frequency range, making it suitable for various applications, including remote control systems, wireless audio, and telemetry. Its lightweight design and user-friendly interface make it an excellent choice for both beginners and seasoned RF enthusiasts.

One of the standout features of the FR146 is its ability to deliver a stable and clean signal. It employs advanced modulation techniques to ensure high-quality transmissions, minimizing interference and distortion. The device supports AM modulation, which is ideal for long-range communication due to its excellent propagation characteristics. This feature is particularly useful in outdoor environments where signals can travel considerable distances.

Another significant advantage of the FR146 is its user-adjustable output power. Users can easily modify the transmitter's power settings to suit specific needs, whether they require low power for short-range applications or higher power for extended reach. This flexibility allows for greater versatility in operation and makes it suitable for various scenarios.

The FR146 also comes equipped with a built-in tone generator, which can be used to encode audio signals. This feature allows for the integration of sound with the RF transmission, making it a perfect choice for projects that require audio broadcasting. Furthermore, the device includes a frequency stabilization circuit, ensuring that the transmitter maintains a consistent frequency even under varying temperature and voltage conditions.

In terms of construction, the FR146 is designed for durability and ease of use. It features a robust enclosure that protects the internal components from environmental factors. The device is straightforward to set up, often requiring only a few simple connections for operation. Its lightweight design enables easy mobility, making it suitable for portable applications.

Overall, the Ramsey Electronics FR146 stands out for its combination of advanced features, robust performance, and ease of use. Whether you are working on a personal project, conducting experiments, or managing professional tasks, the FR146 offers a reliable and effective solution for your RF transmission needs. Its adaptability across different applications makes it a valuable addition to any electronics enthusiast's toolkit.
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