low noise 2 meter pre-amp

2-32 — elektor february 1981 low noise 2 metre preamplifier kw noise 2 metre This preamplifier is intended for use in receivers of the 2 metre amateur band wave (144 MHz). By changing a single resistor, it can be made for either very low noise or a low intermodulation distortion. This is the creation of all kinds of by-products in the output signal which were not in the input signal. The reason for this is that the transistor is not linear. The intermodulation distortion can also be expressed in dB, as the ratio between the desired signal and the intermodu- lation products. For obvious reasons, this ratio should be as high as possible. In other words, an ideal amplifier would have virtually no intermodulation dis- tortion coupled with an extremely low noise factor. It would be ideal if the collector current producing the lowest possible noise could at the same time ensure the lowest possible intermodu- lation distortion. This however is wishful thinking. From the noise point of ...