# Should I add call signs with /R suffix to the logbook?

Sometimes in FT-8 mode I receive calls like this one:

It happens 2-3 times a week.

The problems are: 1) I never could look up such call signs 2) I tried to reply, but never got answer 3) I don't know what /R means.

Are these real calls or maybe just a noise that WSJT-X somehow managed to decode? So far I didn't log such events as QSO's. Maybe I should?

UPD: As Marcus pointed out, the checksum collision in FT-8 is very unlikely. Also I managed to figure out that "/R" means a repeater https://en.wikipedia.org/wiki/Amateur_radio_call_signs I believe it means that the signal was sent automatically by the device, not that the operators works through the repeater. Still I wonder - should I add repeaters to the logbook?

• "noise that WSJT-X somehow managed to decode" <-- that's extremely unlikely; FT-8 does a 12 bit CRC on 75 bit data; the likelihood of a sequence of bit flips breaking both the data and the checksum in a way that looks "valid" again is extemely slim – especially since FT-8 encapsulates these 87 bits in a rate $\frac12$ low-density parity check code. I haven't done the math, but my guess would be that it's more likely that you'll be struck by lightning on your way to pick up your lottery jackpot while randomly happening to be the Queen of England. – Marcus Müller Mar 3 '19 at 12:45
• Thank you, Marcus. I didn't know how long the checksum in FT-8 is. In this case I must agree that the collision is very unlikely. Still I never heard of /R suffix. What could it mean? – Aleksander Alekseev - R2AUK Mar 3 '19 at 12:48
• OK, I manage to figure out that "/R" means a repeater en.wikipedia.org/wiki/Amateur_radio_call_signs I believe it means that the signal was sent automatically by the device, not that the operators works through the repeater. Still I wonder whether I should add repeaters to the logbook. – Aleksander Alekseev - R2AUK Mar 3 '19 at 12:59
• @MarcusMüller The caveat, of course, is that the checksum is subject to the same errors as the message body. – Glenn W9IQ Mar 3 '19 at 14:51
• @MarcusMüller I've definitely seen false decodes, stuff like superficially-Chinese callsigns that don't exist in any database, with grids in the middle of the ocean. The strength of the FT8 code has to be weighed against the sheer number of decodes the software attempts, and its determination to sift out the weakest possible signals. – hobbs - KC2G Mar 6 '19 at 3:44