Novice hams are often hesitant to begin the Assembly of electronic devices just because in the description is missing the picture of the PCB, and to develop its own not everyone can. Indeed, without sufficient experience to make it easy: it is necessary to know how to choose the best dimensions to correctly place items in a timely manner to detect and correct errors. Therefore, we recommend you to master the design of printed circuit boards with the simplest.
The Board size and the location of the printed conductors depend on the number of set a elements and their types, why not get to work, making sure that prepared all the necessary radio components. Pick them in accordance with the concept and description of the instrument and is also considering possible replacements. First of all you need to choose the right types of capacitors: it is important not only capacitance and working voltage that they are designed, but their frequency properties and qualities of the dielectric. If, for example, in the radio frequency device to apply capacitors on the basis of low-frequency ceramic or paper (MBM, BM-2, etc.), it can be generally unworkable.
Fig. 1. The methods of installation of radioelements on PCB
Between mounted on printed circuit Board elements often have complex reciprocal relationships. Their influence could weaken the positioning elements based on the principle of their action and increasing the distance between them. Therefore, you should not strive for reduction of fees due to seal installation. Close the installation may deteriorate and the thermal design of electronic device that interferes with his normal work. In the radio frequency devices is not unnecessarily lengthen the connecting conductors, to arrange the elements of the individual stages in close proximity to each other to be placed close to the input and output circuits.
Fig. 2. Application of the radioactive elements:
a — resistors MLT, b — low power transistors, a capacitor, KM-5, g — condenser K50-6.
Perhaps the greatest difficulties encountered in the development of printed circuit boards amplifiers and oscillators, and increase the operating frequency, gain, number of stages, as well as capacity increase, with increase of requirements to stability of frequency and voltage generated by the task becomes more complicated. The easiest way to develop printed circuit boards for power supplies — just enough to ensure the normal thermal regime elements and, of course, to avoid mistakes. By the way, the errors to the drawing boards need to be identified at all stages of development: the earlier they are detected, the easier it is to fix them.
Hams used both one-sided and double-sided printed circuit Board. Beginners recommend only one-sided. All the radioactive elements in them are on the one hand, and connecting the terminals elements printed conductors on the other.
The methods of installation of components on the Board can be different (Fig. 1). The findings of each of them into the desired shape — curve, to give them a certain configuration, and the location of bends and distance from body to soldering shall conform to the conditions of this element, details of which can be found in the handbooks.
So, transistors can bend the findings are not closer than 2 mm from the body, in turn, the bending radius depends on the diameter of the output than it is thicker, the smaller the allowable curvature. Insights powerful transistors (КТ803, КТ805 and the like), bending is impossible, and semiconductors with the findings of shorter than 10 mm for novice hams better not to use.
The order of placing the electronic components on the PCB is called a layout. From it largely depends on the performance of the electronic device. For example, bad layout of the circuit Board of the generator may cause it unstable, and the radio frequency amplifier to cause self-excitation.