1. First of all the praise. A friend and I have been using WSJT-X for a while now and between us we have over 10,000 FT8 contacts. His preferred mode is FT8 and mine is CW, yet I can work folks on FT8 ( band-counties, prefixes, etc. ) who are not active on other modes. For the most part the program works very well. 2. Caveat. A long time ago I used to develop software for various classified defense/intelligence applications. I understand that when you are writing code that others will use, you need to anticipate all the silly things that people will try to do as well as all the non-silly things that people will want to do of which you would not normally be aware. In that sense, I believe the author(s) of WSJT-X have done a great job and the program works very well for almost everyone because the author(s) have anticipated almost everything. 3. Peculiarities. There are however some peculiarities that my friend and I have observed. These particular peculiarities only seem to apply where someone uses WSJT-X with multiple call signs. Note that these are our apparent “observations” having used the program extensively. No criticism or complaints are intended. And it is possible that what we observe/assume as reproducible peculiarities are merely non-reproducible anomalies. a. One peculiarity seems to be the log file. When you change your call sign, any new contacts show the new call sign while the previous contacts show the previous call sign. That is good. But if you use multiple call signs, and switch back and forth between them, and want to know you haven’t worked someone before ( with whatever call sign you are currently using ), you cannot rely on the log file to tell you. I have a work around. I have a separate WSJT-X log file for each call sign I use ( N4UP, N4UP/M, N4ACW, K7ACW/4, and occasionally other club and special event call signs ). When I switch call signs I change the WSJT-X settings, but I also back up the current WSJT-X log file and then replace it with the one associated with the call sign I am about to use. That way the WSJT-X decode colors are correct for the call sign I am using. This is not terribly inconvenient. No problem. Except my friend is not as computer savvy, so he just uses the one log file. So, his problem, not yours. Obviously this peculiarity means nothing to almost everyone. That’s okay. I am wearing my flame-proof vest. If this post is boring you, please move on. b. Another peculiarity is the way that WSJT-X deals with compound call signs. When we went to Version 2.0 we gained the ability to use compound call signs in WSJT-X. That is great. By compound I mean things like VP9/N4UP and N4UP/M. The problem is not a big one, but does sometimes appear. The problem is what happens when two people are using the same call sign, one not-compound, and one compound, at the same time. For example, I might be using N4ACW and my friend might be using N4ACW/7. We both belong to the club and we are both authorized to use the club call sign, but not on the same band at the same time. We need to be careful to avoid that situation. But yesterday we observed something peculiar. He was working on 20 meters as N4ACW/7 and I was working on 30 meters as N4ACW. Someone ( presumably decent fellow ) was working on 20 meters and ( presumably ) decoded N4ACW/7 on 20 meters but did not work him. Then he moved to 30 meters and called CQ. I responded as N4ACW and he responded to me as if I were N4ACW/7. He thinks I am in Nevada when I am actually in Virginia. I am guessing that he did not erase his decode window when he changed bands, and somehow WSJT-X took the first instance of N4ACW/7 instead of the correct ( second ) instance of N4ACW. My log is presumably correct, but his log is presumably incorrect, wrongly logging N4ACW/7 instead of N4ACW. A polite email should fix that problem. Note. When I say he responded to me as if I were N4ACW/7 I mean the decode was RED on my decode window and my auto-sequence took over. This implies that WSJT-X does not discriminate between compound and non-compound call signs in this sense. At first I feared my friend was also operating on 30 meters but it turned out he was still on 20 meters. Perhaps the problem goes away if people erase the decode window when they change bands ( as I do ), but you cannot count on everyone doing that and I don’t think it would be fair to expect them to. Again this peculiarity means nothing to almost everyone, but if that other operator thinks he worked Nevada when he actually worked Virginia, he might be disappointed. Moreover, N4ACW is good on eQSL and LoTW and N4ACW/7 is not good on either. Now you say people should stick to just one call sign? Sorry you feel that way. We have every right to use a club call sign to the extent that the FCC and the club allow it. So nothing inherently wrong with it. Likewise nothing inherently wrong with mobile and portable operations using compound call signs. Again, no criticism of WSJT-X intended. These are small-rare peculiarities at most.