50W Tube-Valve SW transmitter

This transmitter operates in the shortwave range from 6 MHz to 22 MHz. Coil L1 serves as the shortwave oscillating coil for the 6SA7 vacuum tube and is commercially available. Capacitor C1 is a variable capacitor with a capacitance range of 0 to 500 pF. Coil L1 is constructed with 13 turns of wire, 1 mm in thickness, wound on a form with a diameter of 3 cm. Capacitors C1, C2, C3, and C4 are all variable capacitors, each with a capacitance range of 0 to 500 pF. C3 and C4 should be spaced apart to prevent arcing between their terminals. Coil L3 consists of 13 turns of wire, 1 mm in thickness, wound on a form with a diameter of 4 cm. The base of the 807 vacuum tube must be made of porcelain. The transmitter should be powered using an 80W medium wave transmitter.

The antenna system should have a feed impedance of 75 ohms, with two horizontal sections of the antenna measuring 10 meters each for operation at 6 MHz, reducing to 3.5 meters for operation at 22 MHz. Coordination of the rotation of capacitors C2, C3, and C4 is essential to minimize the current reading on the ammeter, which indicates optimal power radiation.

This transmitter circuit is designed to efficiently generate shortwave signals within the specified frequency range. The use of a 6SA7 tube in conjunction with precisely wound coils and variable capacitors allows for fine-tuning of the oscillation frequency. The variable capacitors (C1, C2, C3, and C4) play a critical role in adjusting the resonant frequency of the circuit, allowing for effective signal transmission.

The construction of the coils is crucial; the dimensions and wire gauge directly influence the inductance and, consequently, the overall performance of the transmitter. The 13 turns in both coils L1 and L3 are optimized for the desired frequency range, ensuring efficient energy transfer and minimal losses.

In terms of the antenna design, the specified lengths for the horizontal sections are vital for matching the transmitter's output impedance to the antenna's feed impedance, which is set at 75 ohms. This matching is critical for maximizing power transfer and minimizing signal reflections. The careful spacing of capacitors C3 and C4 is necessary to mitigate the risk of electrical arcing, which could lead to component failure or signal distortion.

Overall, this transmitter design emphasizes reliability and efficiency, leveraging high-quality components and precise engineering to facilitate effective shortwave communication.This transmitter works in the short waves from 6MC / S to 22MC / S. Coil L1 is the short wave oscillating coil of the 6SA7 lamp and you will find it ready for trade. Capacitor C1 is variable with a capacity of 0-500pF. The coil L1 consists of 13 coils 3cm in diameter and 1mm thick wire. Capacitors C1, C2, C3 and C4 are variables with a capacity of 0-500pF each.

C3 and C4 must be sparse to avoid sparks between their reinforcements. The coil L3 consists of 13 coils of 4 cm diameter, 1 mm thick wire. The base of lamp 807 must be of porcelain. Use the 80W medium wave transmitter to power the transmitter.

The descent of the antenna should be 75Ω and the two horizontal portions of the antenna should each be 10m long for 6MC / S up to 3.5m for 22MC / S. When coordinating with the rotation of capacitors C2, C3 and C4, we must achieve the minimum current in the ammeter.

Then we have the greatest power radiance.