Saturday, August 10, 2013

matching network for the antenna feed line

To match the output stage of the transmitter antenna to the power line, you can use proprietary matching devices for example mfj. But if you do not have or can not buy it, then you can build a device to align antennas shown in the figure. This is a matching device used to adapt the output of the transmitter with a resistance of 50 ohms with balanced and unbalanced power line connected to the antenna input impedance from 10 to 4000 ohms. Between the transmitter output and the input matching device placed SWR. After SWR transmitter signal applied to the input matching circuit devices for L1-C1 (L1A-C1, L1B-C1) which has inductive coupling with the antenna circuit. Setting the Loop L1-C1 made pripomoschi capacitor C1. Setting the antenna circuit L2-C2 (L2AB-C2C3) made capacitors C2 and C3. By the antenna circuit may be connected balanced or unbalanced load. The adjustment is made independent of each other capacitors C2 and C3. Switch matching device has four sections at five positions (or more depending on the number of bands). Coils L1A and L1B has four turns in the range of 80 and 40 meters, both coils are connected in series (8 turns), other bands parallel. Parallel connection improves the agreement with the 50 ohm output of the transmitter. All coils are wound on a device matching the same frame having a diameter of 75 mm. Coils L2A and L2B are approximately 28-30 turns. Since capacitors matching device are under a lot of stress, they must be isolated from each other and from the metal housing of the device, the handle on the axes of the capacitors should also be insulated. The second figure shows the performance of the matching coil unit.

matching network

design matching device

No comments:

Post a Comment