What is the PGA setting used for in the Configuration menu?
PGA stands for Programmable Gain Amplifier, which happens to be U7 in the schematic. This device can be set to different levels of amplification to better handle either low-level or high-level audio signals coming into the modem from the transceiver. Normally there is no need to change the setting of the PGA. The default setting is a voltage gain of 16. The PgUp key can increase the gain to a maximum of 32. The PgDn key can decrease the gain to a minimum of 1. In some cases, with a very strong signal near a weaker signal that you are trying to copy, reducing the gain may help in decoding the PSK signal. An alternative (which I frequently use) is to reduce the RF gain of the receiver, so that there is little AGC action due to the very strong signal. Because of the limited dynamic range of the electronics, reducing the gain, or the signal level of the input, can prevent “clipping” of the audio signal in the Modem. Generally, you will find that the Modem will demodulate signals that are b
