Switching ON and OFF of the VBF always interacts with RGO ONE receiver Automatic gain control system (AGC). Since VBF reduces noises in RX path – from the ether and from previous IF amplifier, AGC system will act slightly different. Let’s discuss these cases:
1. VBF is not in use (or not installed) AGC treshold is aligned with R26 on IF/AF board in order to obtain S1 or no indication on S-meter. (This procedure has been already done by manufacturer)
2. VBF is installed and is selected (B01 – B10) via pressing FLT button. IF signal + noise is decreased and then AGC response and action will be decreased. Reading on S-meter will fall down. AGC treshold must be realigned with R26 potentiometer in order to have proper AGC response and S-meter reading. But if you decide to switch VBF off and use standard filter again – S-meter reading will not be valid and R26 must be realigned again.
How to deal this issue.
1. If you like to achieve best AGC response and you are mostly CW operator and you are using mainly narrow filters – then engage VBF and align R26 to null S-meter reading with no antenna connected to RGO ONE 50 ohm input. First rotate R26 counterclockwise and when S-meter starts to raise – slightly and carefully return back till S1 on S-meter flickers or no segments appear lit on LCD. In order to achieve true S-meter readings – always use VBF – for CW and sideband modes – just increase or reduce bandwith with encoder 1 on the front panel.
2. If you are not using narrow filter much – align AGC treshold with R26 when VBF is off or do not align it if S-meter reading is null (with no antenna connected). Though S-meter reading might not be accurate on some filter bandwiths when VBF is on. Received signal strength won’t degrade or been lost with this adjustment. Just S-meter reading will show some S units.