I keep forgetting questions like this is why we have Google, it isn't necessary to embarass yourself by asking them publicly.

As soon as I posted, I did a search and it led me to some of the same places you went to. I did notice that my "several minutes"
interval was bogus, several seconds is more realistic. I suspect it was an artifact of Lunan's book. I must have read it a long time ago.

However, I did remember that figure correctly, because I recall at the time doing the calculations and I determined that a Bracewell probe with those signal characteristics would have to be somewhere in the inner solar system.

Thanks for checking up on that for us.