So, setting LNA manually to G1 yields the following results:

`1.0. RSSI=-102, regAFCFEI=B10000, regLNA=B1001`

1.1. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

1.2. RSSI=-112, regAFCFEI=B10000, regLNA=B1001

1.3. RSSI=-105, regAFCFEI=B10000, regLNA=B1001

1.4. RSSI=-108, regAFCFEI=B10000, regLNA=B1001

1.5. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

1.6. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

1.7. RSSI=-109, regAFCFEI=B10000, regLNA=B1001

1.8. RSSI=-111, regAFCFEI=B10000, regLNA=B1001

1.9. RSSI=-114, regAFCFEI=B10000, regLNA=B1001

2.0. RSSI=-98, regAFCFEI=B10000, regLNA=B1001

2.1. RSSI=-109, regAFCFEI=B10000, regLNA=B1001

2.2. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

2.3. RSSI=-127, regAFCFEI=B10000, regLNA=B1001

2.4. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

2.5. RSSI=-115, regAFCFEI=B10000, regLNA=B1001

2.6. RSSI=-109, regAFCFEI=B10000, regLNA=B1001

2.7. RSSI=-107, regAFCFEI=B10000, regLNA=B1001

2.8. RSSI=-116, regAFCFEI=B10000, regLNA=B1001

2.9. RSSI=-112, regAFCFEI=B10000, regLNA=B1001

3.0. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

3.1. RSSI=-114, regAFCFEI=B10000, regLNA=B1001

3.2. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

3.3. RSSI=-104, regAFCFEI=B10000, regLNA=B1001

3.4. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

3.5. RSSI=-108, regAFCFEI=B10000, regLNA=B1001

3.6. RSSI=-112, regAFCFEI=B10000, regLNA=B1001

3.7. RSSI=-104, regAFCFEI=B10000, regLNA=B1001

3.8. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

3.9. RSSI=-108, regAFCFEI=B10000, regLNA=B1001

4.0. RSSI=-105, regAFCFEI=B10000, regLNA=B1001

4.1. RSSI=-114, regAFCFEI=B10000, regLNA=B1001

4.2. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

4.3. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

4.4. RSSI=-107, regAFCFEI=B10000, regLNA=B1001

4.5. RSSI=-111, regAFCFEI=B10000, regLNA=B1001

4.6. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

4.7. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

4.8. RSSI=-109, regAFCFEI=B10000, regLNA=B1001

4.9. RSSI=-109, regAFCFEI=B10000, regLNA=B1001

5.0. RSSI=-102, regAFCFEI=B10000, regLNA=B1001

5.1. RSSI=-112, regAFCFEI=B10000, regLNA=B1001

5.2. RSSI=-111, regAFCFEI=B10000, regLNA=B1001

5.3. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

5.4. RSSI=-107, regAFCFEI=B10000, regLNA=B1001

5.5. RSSI=-109, regAFCFEI=B10000, regLNA=B1001

5.6. RSSI=-110, regAFCFEI=B10000, regLNA=B1001

5.7. RSSI=-107, regAFCFEI=B10000, regLNA=B1001

5.8. RSSI=-106, regAFCFEI=B10000, regLNA=B1001

5.9. RSSI=-104, regAFCFEI=B10000, regLNA=B1001

Setting LNA manually to G2 (which is what the AGC was selecting) yields:

`1.0. RSSI=-103, regAFCFEI=B10000, regLNA=B10010`

1.1. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

1.2. RSSI=-107, regAFCFEI=B10000, regLNA=B10010

1.3. RSSI=-108, regAFCFEI=B10000, regLNA=B10010

1.4. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

1.5. RSSI=-106, regAFCFEI=B10000, regLNA=B10010

1.6. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

1.7. RSSI=-106, regAFCFEI=B10000, regLNA=B10010

1.8. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

1.9. RSSI=-103, regAFCFEI=B10000, regLNA=B10010

2.0. RSSI=-100, regAFCFEI=B10000, regLNA=B10010

2.1. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

2.2. RSSI=-106, regAFCFEI=B10000, regLNA=B10010

2.3. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

2.4. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

2.5. RSSI=-101, regAFCFEI=B10000, regLNA=B10010

2.6. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

2.7. RSSI=-109, regAFCFEI=B10000, regLNA=B10010

2.8. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

2.9. RSSI=-101, regAFCFEI=B10000, regLNA=B10010

3.0. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

3.1. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

3.2. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

3.3. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

3.4. RSSI=-107, regAFCFEI=B10000, regLNA=B10010

3.5. RSSI=-103, regAFCFEI=B10000, regLNA=B10010

3.6. RSSI=-107, regAFCFEI=B10000, regLNA=B10010

3.7. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

3.8. RSSI=-106, regAFCFEI=B10000, regLNA=B10010

3.9. RSSI=-103, regAFCFEI=B10000, regLNA=B10010

4.0. RSSI=-107, regAFCFEI=B10000, regLNA=B10010

4.1. RSSI=-106, regAFCFEI=B10000, regLNA=B10010

4.2. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

4.3. RSSI=-113, regAFCFEI=B10000, regLNA=B10010

4.4. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

4.5. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

4.6. RSSI=-107, regAFCFEI=B10000, regLNA=B10010

4.7. RSSI=-103, regAFCFEI=B10000, regLNA=B10010

4.8. RSSI=-107, regAFCFEI=B10000, regLNA=B10010

4.9. RSSI=-108, regAFCFEI=B10000, regLNA=B10010

5.0. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

5.1. RSSI=-101, regAFCFEI=B10000, regLNA=B10010

5.2. RSSI=-101, regAFCFEI=B10000, regLNA=B10010

5.3. RSSI=-104, regAFCFEI=B10000, regLNA=B10010

5.4. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

5.5. RSSI=-102, regAFCFEI=B10000, regLNA=B10010

5.6. RSSI=-105, regAFCFEI=B10000, regLNA=B10010

5.7. RSSI=-101, regAFCFEI=B10000, regLNA=B10010

5.8. RSSI=-100, regAFCFEI=B10000, regLNA=B10010

5.9. RSSI=-109, regAFCFEI=B10000, regLNA=B10010

Setting LNA manually to G6 (which is what the AGC was selecting) yields:

`1.0. RSSI=-66, regAFCFEI=B10000, regLNA=B110110`

1.1. RSSI=-70, regAFCFEI=B10000, regLNA=B110110

1.2. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

1.3. RSSI=-63, regAFCFEI=B10000, regLNA=B110110

1.4. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

1.5. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

1.6. RSSI=-71, regAFCFEI=B10000, regLNA=B110110

1.7. RSSI=-67, regAFCFEI=B10000, regLNA=B110110

1.8. RSSI=-68, regAFCFEI=B10000, regLNA=B110110

1.9. RSSI=-64, regAFCFEI=B10000, regLNA=B110110

2.0. RSSI=-62, regAFCFEI=B10000, regLNA=B110110

2.1. RSSI=-63, regAFCFEI=B10000, regLNA=B110110

2.2. RSSI=-63, regAFCFEI=B10000, regLNA=B110110

2.3. RSSI=-67, regAFCFEI=B10000, regLNA=B110110

2.4. RSSI=-70, regAFCFEI=B10000, regLNA=B110110

2.5. RSSI=-68, regAFCFEI=B10000, regLNA=B110110

2.6. RSSI=-63, regAFCFEI=B10000, regLNA=B110110

2.7. RSSI=-72, regAFCFEI=B10000, regLNA=B110110

2.8. RSSI=-70, regAFCFEI=B10000, regLNA=B110110

2.9. RSSI=-67, regAFCFEI=B10000, regLNA=B110110

3.0. RSSI=-62, regAFCFEI=B10000, regLNA=B110110

3.1. RSSI=-72, regAFCFEI=B10000, regLNA=B110110

3.2. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

3.3. RSSI=-69, regAFCFEI=B10000, regLNA=B110110

3.4. RSSI=-66, regAFCFEI=B10000, regLNA=B110110

3.5. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

3.6. RSSI=-70, regAFCFEI=B10000, regLNA=B110110

3.7. RSSI=-62, regAFCFEI=B10000, regLNA=B110110

3.8. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

3.9. RSSI=-63, regAFCFEI=B10000, regLNA=B110110

4.0. RSSI=-63, regAFCFEI=B10000, regLNA=B110110

4.1. RSSI=-60, regAFCFEI=B10000, regLNA=B110110

4.2. RSSI=-69, regAFCFEI=B10000, regLNA=B110110

4.3. RSSI=-68, regAFCFEI=B10000, regLNA=B110110

4.4. RSSI=-72, regAFCFEI=B10000, regLNA=B110110

4.5. RSSI=-68, regAFCFEI=B10000, regLNA=B110110

4.6. RSSI=-69, regAFCFEI=B10000, regLNA=B110110

4.7. RSSI=-75, regAFCFEI=B10000, regLNA=B110110

4.8. RSSI=-65, regAFCFEI=B10000, regLNA=B110110

4.9. RSSI=-74, regAFCFEI=B10000, regLNA=B110110

5.0. RSSI=-66, regAFCFEI=B10000, regLNA=B110110

5.1. RSSI=-66, regAFCFEI=B10000, regLNA=B110110

5.2. RSSI=-71, regAFCFEI=B10000, regLNA=B110110

5.3. RSSI=-64, regAFCFEI=B10000, regLNA=B110110

5.4. RSSI=-68, regAFCFEI=B10000, regLNA=B110110

5.5. RSSI=-67, regAFCFEI=B10000, regLNA=B110110

5.6. RSSI=-66, regAFCFEI=B10000, regLNA=B110110

5.7. RSSI=-66, regAFCFEI=B10000, regLNA=B110110

5.8. RSSI=-68, regAFCFEI=B10000, regLNA=B110110

5.9. RSSI=-69, regAFCFEI=B10000, regLNA=B110110

So, given the difference between manually setting LNA to G2 versus letting AGC set the LNA to G2, the manual setting seems less anomalous.

Theoretically, with a shorted antenna, all the RSSI values should be -127, at least ideally. Isn't that right? Looking at the above results, the only time I get even one measurement with RSSI=-127 is when LNA is set to G1.

Bottom line: when just measuring ambient RSSI, is it best to manually set LNA to G1?

On the other hand, suppose you determine empirically that when receiving packets from a particular RFM69 Moteino, the AGC is generally using a gain of G2. In that case, maybe setting LNA manually to G2 would be the more relevant choice, because then you'd be measuring the background RSSI at the LNA level that's most relevant to receiving packets from that particular RFM69 Moteino. Isn't that right?

I'm just feeling my way through the dark here, so any and all comments/suggestions/help/guidance would be more than welcome.

Not to overcomplicate the discussion, but does DC cancellation figure into this at all? Quoting the datasheet: "DC cancellation is required in zero-IF architecture transceivers to remove any DC offset generated through self-reception." What kind of "self-reception" is it referring to? i.e. Is that "self-reception" the result of the transceiver's own transmission, or is it "self-reception" of the noise created by the RFM69 in normal operation?

The datasheet also says, "It is advised to adjust the DCC setting while monitoring the receiver sensitivity." How does one even do that? I've searched this forum and haven't found any meaningful postings about DCC.