ACS of Amateur Radio

ACS is short for Adjacent Channel Selectivity. It is a measure of the receiver's ability to receive useful modulated signals and is an important parameter of radio receivers.

The definition of adjacent channel selectivity is the ratio of the attenuation of the receiver filter on the specified channel to the attenuation on the adjacent channel. Therefore, when defining adjacent channel selectivity, that is, ACS performance, the performance of the receiver filter is the key.

​There are some points that we should pay attention to when testing the Adjacent Channel Selectivity of radio receivers.

1. The frequency of the useful signal should be consistent with the nominal frequency of the receiver;

2. The useful signal level should be set to be consistent with the maximum available sensitivity;

3. Adjacent channels are selectively expressed by the smaller value of the ratio of the unwanted signal level and the useful signal level on the upper and lower adjacent channels;

4. Under extreme conditions, set the useful signal level value to the maximum available sensitivity to repeat the test

Under normal conditions, the adjacent channel selection rate should not be less than 70dB; under extreme conditions, it should not be less than 60dB. The useful modulation signal does not exceed the given attenuation due to the existence of the useless modulation signal, and the frequency offset between the useless signal and the useful signal is 25kHz.