Simple 15W linear on KV
The described power amplifier is suitable as a supplement to the all-band QRPP TCVR with a power of 1W and less. In bands 160 up to 10m will transmit approx 10 up to 15W. The construction is simple and undemanding, it does not hide any intricacies.
The PA is fitted with a 2SC1969 transistor (Uce = 13.8V, Ic = 6A, Ptot = 35W, G = 11.5dB at 30 MHz, Ft = 90 MHz, Pout = 16W), which is cheap and available. It is of course possible to use another similar transistor.
The excitation is supplied through the input transformer TR1. The quiescent current circuit consists of R1, D1, C1 a C2. Resistor R1 sets the quiescent current to 75mA. Diode D1 should have thermal contact with the transistor case, which must be mounted on the radiator. The stability of the connection is improved by the negative feedback of R2C3. Due to the wide range of transmitted frequencies, two chokes are used. The output transformer TR2 is wound on a pair of glued toroids made of material T50-61.
The setting of the amplifier is limited to the quiescent current setting. To begin with, we choose R1 of a significantly larger value (2,2k a pod.), which we then slowly reduce, until we reach a quiescent current of 75mA.
| R1 | cca.470 * |
| R2 | 100 0,5W |
| R3 | 22 |
| R4 | 2,2k 1W |
| C1 | 100nF |
| C2 | 22uF/6V |
| C3 | 47nF |
| C4 | 100nF |
| C5 | 22uF/16V tantalum |
| C6 | 47nF |
| D1 | 1N4001 a pod. |
| T | 2SC1969 |
| TL1 | 8uH 35z toroid T68-2 |
| TL2 | 4z na ferit.perle |
| TR1 | 30/8z toroid T50-61 |
| TR2 | 8/20from two T50-61 toroids |
