Why use such a fancy interface? Why not just wire the tuner to the radios connector as shown on the SGC web page?
A. The simple circuit, even the one using the resistor and capacitor, can cause reliability problems. The radio outputs a short (appox 60mS) pulse for each band change. This is intended to signal Icom’s AH-4 tuner to go into bypass mode. With the direct connections, this band change pulse can cause the radio to inadvertently go into tune while changing bands. This is especially true if you step through several bands to get to the one you want. The multiple pulses can charge the capacitor to the point where it trips the radio into tune right in the middle of changing bands You wind up putting a tune signal on a randomly selected frequency which may be right on top of a QSO in progress. In addition, the radio’s tune button does not function as Icom intended when using the simple circuit. The SGC tuner does not send the proper control signals to the radio to indicate if it was able to find a proper match or not. The cancel tune and bypass functions do not work as Icom intended for the sam
