80M-amateur-radio-transmitter
This transmitter comprises a keyed crystal oscillator/driver and a high-efficiency final amplifier, both utilizing a TMOS Power FET as the active component. The total cost of components is under $20, and no specialized construction skills or circuit boards are necessary. The Pierce oscillator is distinctive due to the high capacitance of the final amplifier's power FET, ranging from 700 to 1200 pF, which is incorporated into the capacitive feedback network. The oscillator will not function without the installation of Q2. The MPF910 transistor is a suitable choice for this circuit as it can drive the final amplifier in a switching mode while maintaining sufficient gain for oscillation. To reduce costs, a commonly available color burst TV crystal serves as the frequency-determining element for Q1. An impressive output efficiency of 84% can be achieved with this transmitter, attributed to the characteristics of the TMOS power FET and modifications to the conventional algorithm for output matching.
This transmitter circuit is designed to operate efficiently while remaining cost-effective. The core of the design is the keyed crystal oscillator, which utilizes a Pierce configuration. This configuration relies on the unique properties of the TMOS Power FET, which not only serves as the active element but also plays a critical role in determining the oscillator's performance. The inclusion of the high capacitance from the final amplifier's FET into the feedback network is a notable feature, as it enhances the oscillator's stability and frequency accuracy.
The choice of the MPF910 transistor is strategic; it is capable of functioning in a switching mode, which is essential for driving the final amplifier effectively. This allows the transmitter to achieve high output power while minimizing power loss, which is crucial for maintaining the overall efficiency of the system. The use of a color burst TV crystal as the frequency-determining element is a practical decision that leverages readily available components, further reducing the overall cost of the circuit.
The design achieves an output efficiency of 84%, which is significantly high for a transmitter of this nature. This efficiency is primarily due to the inherent characteristics of the TMOS power FET, which allows for lower on-resistance and faster switching speeds compared to traditional FETs. Additionally, the modifications made to the output matching algorithm optimize the power transfer from the final amplifier to the antenna, ensuring that most of the generated power is effectively radiated.
Overall, this transmitter circuit is an excellent example of how thoughtful design choices and component selection can lead to high performance in a compact and economical package. The integration of the TMOS Power FET, the use of standard components, and the innovative feedback network design collectively contribute to a reliable and efficient transmitter suitable for various applications.This transmitter consists of a keyed crystal oscillator/driver and a high efficiency final, each with a TMOS Power FET as the active element. The total parts cost less than $20, and no special construction skills or circuit boards are required.
The Pierce oscillator is unique because the high 4ss of the final amplifier power FET, 700 -1200 pF, is used as part of the capacitive feedback network. In fact, the oscillator will not work without Q2 installed. The MPF910 is a good choice for this circuit because the transistor is capable of driving the final amplifier in a switching-mode, while still retaining enough gain for oscillation. To minimize cost, a readily-available color burst TV crystal is used as the frequency-determining element for Ql.
An unusual 84% output efficiency is possible with this transmitter. Such high efficiency is achieved because of the TMOS power FET"s characteristics, along with modification of the usual algorithm for determining output matching. 🔗 External reference
This transmitter circuit is designed to operate efficiently while remaining cost-effective. The core of the design is the keyed crystal oscillator, which utilizes a Pierce configuration. This configuration relies on the unique properties of the TMOS Power FET, which not only serves as the active element but also plays a critical role in determining the oscillator's performance. The inclusion of the high capacitance from the final amplifier's FET into the feedback network is a notable feature, as it enhances the oscillator's stability and frequency accuracy.
The choice of the MPF910 transistor is strategic; it is capable of functioning in a switching mode, which is essential for driving the final amplifier effectively. This allows the transmitter to achieve high output power while minimizing power loss, which is crucial for maintaining the overall efficiency of the system. The use of a color burst TV crystal as the frequency-determining element is a practical decision that leverages readily available components, further reducing the overall cost of the circuit.
The design achieves an output efficiency of 84%, which is significantly high for a transmitter of this nature. This efficiency is primarily due to the inherent characteristics of the TMOS power FET, which allows for lower on-resistance and faster switching speeds compared to traditional FETs. Additionally, the modifications made to the output matching algorithm optimize the power transfer from the final amplifier to the antenna, ensuring that most of the generated power is effectively radiated.
Overall, this transmitter circuit is an excellent example of how thoughtful design choices and component selection can lead to high performance in a compact and economical package. The integration of the TMOS Power FET, the use of standard components, and the innovative feedback network design collectively contribute to a reliable and efficient transmitter suitable for various applications.This transmitter consists of a keyed crystal oscillator/driver and a high efficiency final, each with a TMOS Power FET as the active element. The total parts cost less than $20, and no special construction skills or circuit boards are required.
The Pierce oscillator is unique because the high 4ss of the final amplifier power FET, 700 -1200 pF, is used as part of the capacitive feedback network. In fact, the oscillator will not work without Q2 installed. The MPF910 is a good choice for this circuit because the transistor is capable of driving the final amplifier in a switching-mode, while still retaining enough gain for oscillation. To minimize cost, a readily-available color burst TV crystal is used as the frequency-determining element for Ql.
An unusual 84% output efficiency is possible with this transmitter. Such high efficiency is achieved because of the TMOS power FET"s characteristics, along with modification of the usual algorithm for determining output matching. 🔗 External reference