I was looking at different radio designs on the net and the amateur band only radios have a single bandpass filter switched in and out for each ham band. But I have used many general coverage radios for example the kenwood ts850 which as you tune you hear a relay switch at every half megahertz, inside and outside any ham band. That would mean the radio would need 56 band pass filters which is clearly overkill. So can someone explain what is happening here, i.e are bandpass filters combined in series like gearsticks on a truck to lower the number needed or what?