I’d been keeping an eye on the F5LEN and Hepburn Atlantic tropo forecasts prior to the 20th of May because they looked promising for good propagation towards the south:
 Hepburn North Atlantic forecast 06z May 20, 2015 |  F5LEN Atlantic forecast 00z 21st May, 2015 |
Lots of bright colours over much of the North Atlantic! There looked to be some possibility of a repeat of Dave, PJ4VHF’s incredible reception of the Cape Verde beacon, over a distance of some 4700km (and perhaps further?), as well as a north-south path touching on Ireland.
Up until lunchtime on the 20th there was nothing other than a slight enhancement on my AIS receiver (a useful propagation tool at 162MHz, online at MarineTraffic) showing ships slightly further south of Cork than usual – certainly nothing exceptional. I wasn’t even hearing the stalwart ED1ZAG beacon in IN53 but the forecast maps were marginal for that direction.
At approximately 14:35z, a weak cw-keyed signal appeared just very slightly above 144.436MHz, rapidly becoming strong enough to identify as D4C in HK76mv! The Monteverde Contest Team’s beacon is at a distance of some 4165km from EI3KD, with a tolerance of five kilometers or so, which probably makes it the furthest tropo distance yet heard from within IARU Region 1.