Signal strength reports?
I'm holding off on a couple of potential bug reports because I now realize I may not correctly understand the various signal strength reports that appear in the VarAC UI and in the logs.
In recent tests using FM, we had inconsistent broadcast reception, and QSOs were disconnected seemingly at random. In the UI, my partner was seeing the SNR(dB) Last and Avg of my signal around +16. I may have mis set expectations from FT8, where I expect solid communications down to -10 or so. If I look at N7SHM's VARA FM log I'm seeing:
2023-03-23 17:04:11 Monitor: WA1TYB -> N7SHM S/N: 19.2 dB
2023-03-23 17:04:45 Monitor: Weak Incoming signal (Unknown) S/N: 15.9 dB
2023-03-23 17:06:31 Monitor: WA1TYB -> N7SHM S/N: 17.5 dB
2023-03-23 17:07:21 Monitor: Weak Incoming signal (Unknown) S/N: 10.8 dB
I thought that 10dB would be quite a strong signal, so I'm unsure what is being reported here
I'm also seeing:
.2023-03-23 17:10:38 Connecting to WA1TYB... 1/2
2023-03-23 17:10:40 Connected to WA1TYB
2023-03-23 17:10:42 <-SN
2023-03-23 17:10:45 <-SN
2023-03-23 17:11:11 Poor conditions. Disconecting...
2023-03-23 17:11:12 WA1TYB disconnected TX: 11 Bytes (Max: 566 bps) RX: 19 Bytes (Max: 566 bps) Session Time: 00:32
2023-03-23 17:13:34 Connecting to WA1TYB... 1/2
2023-03-23 17:13:36 Connected to WA1TYB
2023-03-23 17:13:38 <-SN
2023-03-23 17:13:41 <-SN
2023-03-23 17:14:26 Poor conditions. Disconecting...
2023-03-23 17:14:27 WA1TYB disconnected TX: 45 Bytes (Max: 566 bps) RX: 19 Bytes (Max: 566 bps) Session Time: 00:51
2023-03-23 17:15:01 <-SN
2023-03-23 17:15:01 WA1TYB connected S/N: 26.4 dB
2023-03-23 17:15:01 <-LINK REGISTERED
2023-03-23 17:15:31 Poor conditions. Disconecting...
2023-03-23 17:15:33 WA1TYB disconnected TX: 45 Bytes (Max: 566 bps) RX: 19 Bytes (Max: 566 bps) Session Time: 00:32
Unfortunately, the VARA FM Log doesn't record a S/N for the poor conditions. But looking at that period in my (WA1TYB) traffic log at 17:13:43 I get a signal report of +23:
23/03/2023 17:10:39 - CONNECTED TO N7SHM
23/03/2023 17:10:46 - WA1TYB> de WA1TYB <R+02>
23/03/2023 17:10:47 - N7SHM> Second "23/03/2023 17:11:12 - QSO SUMMARY: Frequency: 145.050.000 (2m) Duration: 00:00:32
23/03/2023 17:11:12 - DISCONNECTED FROM N7SHM
23/03/2023 17:13:35 - INCOMING CONNECTION REQUEST. Still don't know who that is.
23/03/2023 17:13:35 - CONNECTED TO N7SHM
23/03/2023 17:13:42 - WA1TYB> de WA1TYB <R+01>
23/03/2023 17:13:43 - N7SHM> Second "New message" test
de N7SHM <R+24>
23/03/2023 17:14:27 - QSO SUMMARY: Frequency: 145.050.000 (2m) Duration: 00:00:51
23/03/2023 17:14:27 - DISCONNECTED FROM N7SHM
23/03/2023 17:15:02 - INCOMING CONNECTION REQUEST. Still don't know who that is.
23/03/2023 17:15:02 - CONNECTED TO N7SHM
23/03/2023 17:15:32 - QSO SUMMARY: Frequency: 145.050.000 (2m) Duration: 00:00:29
23/03/2023 17:15:32 - DISCONNECTED FROM N7SHM
And in his (N7SHM) traffic log I send him a +02 and a +01:
23/03/2023 17:10:40 - INCOMING CONNECTION REQUEST. Still don't know who that is.
23/03/2023 17:10:40 - CONNECTED TO WA1TYB
23/03/2023 17:10:42 - WA1TYB> de WA1TYB <R+02>
23/03/2023 17:11:12 - QSO SUMMARY: Frequency: 0 () Duration: 00:00:31
23/03/2023 17:11:12 - DISCONNECTED FROM WA1TYB
23/03/2023 17:13:36 - INCOMING CONNECTION REQUEST. Still don't know who that is.
23/03/2023 17:13:36 - CONNECTED TO WA1TYB
23/03/2023 17:13:38 - WA1TYB> de WA1TYB <R+01>
23/03/2023 17:14:02 - N7SHM> Second "New message" test
de N7SHM <R+24>
23/03/2023 17:14:27 - QSO SUMMARY: Frequency: 0 () Duration: 00:00:50
23/03/2023 17:14:27 - DISCONNECTED FROM WA1TYB
23/03/2023 17:15:02 - INCOMING CONNECTION REQUEST. Still don't know who that is.
23/03/2023 17:15:02 - CONNECTED TO WA1TYB
23/03/2023 17:15:33 - QSO SUMMARY: Frequency: 0 () Duration: 00:00:30
23/03/2023 17:15:33 - DISCONNECTED FROM WA1TYB
All of these disconnects were the result of "Poor conditions" at the N7SHM end. When he's giving me +24. There is something I'm clearly not understanding. Where am I going wrong?
I've uploaded the six logs as a zip attached to this report..
Generally speaking - FM is not like SSB when it comes to SNR levels. With FM on one hand you can send more data but you need a solid copy. SSB is more tolerable with faint signals. Thats why the Modem consider those SNR levels as poor as relatively to FM, they are poor. Try the same link over USB on 2M/70CM and you'll notice the difference... but the Max speed level of VARAHF will be lower.