ˆ3. Connect a dummy load to J1, the amplifier RF output. In a pinch, a light bulb may be used - see the section, "Verifying RF Power Output."

ˆ4. Temporarily install a jumper from the collector of Q3 to ground.

ˆ5. Apply power to the amplifier but do not turn on the transmitter. Measure the current drawn by the amplifier and slowly rotate the bias pot, R4, clockwise until you reach a reading of ¼ amp. Do not allow the current to rise above ½ amp. If you cannot adjust or reduce the current, disconnect the power supply and consult the troubleshooting hints section. The voltage at TP1 should be about 3.2 to 3.5 volts.

ˆ6. Turn off power. Disconnect jumper from Q3 to ground.

ˆ7. Connect the QRP transmitter to the input of the amplifier. Key the transmitter. You should hear the T-R relay click and see amplified power output. Measure the DC current draw; it should be in the 1 to 3 amp range depending upon power output. Unkey the transmitter. The relay should drop out and the current should drop back down to ¼ amp

This completes the testing of your QRP power amplifier. The PC board should be mounted into a protective enclosure to guard against accidental contact. The Ramsey CQAMP case set provides an ideal perfectly sized cabinet that matches all other Ramsey kits.

Study the following sections on DC power supply and RF power considerations. Operate your transmitter with good amateur practice.

YOUR POWER SUPPLY AND RF OUTPUT POWER

For optimum performance, one or two volts of extra DC supply power can make quite a difference in any RF power amplifier. For example, two lantern batteries in series, or 8 D cells, will obviously provide about 12 volts with sufficient current capability for casual operating. For maximum RF output power, use a supply of 13 to 14 volts DC. The easiest method is to place two fresh D cells in series with your power source if a full 13.6 - 15 volts DC is not available. Be aware that batteries are not the optimum power source, especially if you are prone to long QSOs! A word of caution concerning wall plug style AC adapter power supplies: They are not suitable for operation of your amplifier due to their poor regulation, AC ripple content, and RFI susceptibility.

With 1 watt of drive and a supply voltage in the 11-12 volt range, you can expect a 1 to 2 amp current draw and about 10 watts of RF output power. With a solid 13 to 14 volt supply, you can expect about 2 to 3 amps current draw and up to 10 or 12 watts of RF output power. With 2 watts of RF drive, expect up to 20 watts RF output!

QAMP-40 • 13

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Ramsey Electronics QAMP40 manual Your Power Supply and RF Output Power
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QAMP40 specifications

The Ramsey Electronics QAMP40 represents a notable advancement in the world of audio amplification, catering to both DIY enthusiasts and professional users alike. This compact, yet powerful audio amplifier is designed for high performance while maintaining ease of use and versatility, making it an excellent choice for various applications, from home audio systems to automotive setups.

One of the main features of the QAMP40 is its robust power output, delivering 40 watts per channel into an 8-ohm load. This capability allows it to drive a wide range of speakers effectively, producing clear and dynamic sound. Users can enjoy enhanced audio quality whether for casual listening, home theater setups, or more demanding audio applications.

The QAMP40 utilizes a Class D amplifier topology, known for its efficiency and minimized heat generation compared to traditional analog amplifiers. This technology not only ensures that the amplifier can operate quietly without the need for extensive heat dissipation measures but also allows longer play times on battery-operated systems. The compact form factor makes it easy to integrate into smaller spaces where traditional amplifiers might struggle.

Another standout characteristic of this amplifier is its versatile input options. The QAMP40 includes both RCA line-level inputs and a 3.5mm auxiliary input, allowing seamless connectivity with various audio sources, including smartphones, tablets, and CD players. This flexibility enables users to easily switch between different devices without the hassle of constantly reconfiguring their audio setup.

Further enhancing its appeal is the QAMP40's user-friendly design. The front panel features a simple volume control knob and a power switch, making it straightforward for users to operate without any complex configurations. The amplifier also comes with built-in protection circuitry, safeguarding the internal components from overload and short circuits, thus ensuring reliability and longevity.

In summary, the Ramsey Electronics QAMP40 is an excellent audio amplification solution that combines compact design, powerful output, and advanced technology. Its Class D architecture, versatile inputs, and user-friendly interface make it suitable for a wide range of applications. Whether you are an audio professional seeking a powerful amplifier or a hobbyist looking to enhance your sound system, the QAMP40 offers a compelling blend of performance and convenience that can meet diverse audio needs. Invest in the QAMP40 to elevate your listening experience today.
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