How to use the adjustment wheel on Philips antenna's amplifier?

The amplifier gain is variable. Fully clockwise is most gain. After positioning the antenna to align with the direction of the broadcasting station - increase the amount of gain to about 1/4. Scan for local stations. If you receive the expected number of stations - then you are most likely in the correct area of gain. If you are missing some stations gradually increase the gain to see if you can receive the stations. You may also experiment with placement of the antenna. Best reception is often near a window facing the transmitters. Do not use more gain than is required to receive the stations. It may be required to adjust gain to an individual station