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This is the first of two papers describing the observations and cataloguingof deep 3-GHz observations of the Lockman Hole North using the Karl G. JanskyVery Large Array. The aim of this paper is to investigate, through the use ofsimulated images, the uncertainties and accuracy of source-finding routines, aswell as to quantify systematic effects due to resolution, such as sourceconfusion and source size. While these effects are not new, this work isintended as a particular case study that can be scaled and translated to othersurveys. We use the simulations to derive uncertainties in the fittedparameters, as well as bias corrections for the actual catalogue (presented inPaper 2). We compare two different source-finding routines, OBIT and AEGEAN,and two different effective resolutions, 8 and 2.75 arcsec. We find that thetwo routines perform comparably well, with OBIT being slightly better atde-blending sources, but slightly worse at fitting resolved sources. We showthat 30 to 70 per cent of sources are missed or fit inaccurately once thesource size becomes larger than the beam, possibly explaining source counterrors in high-resolution surveys. We also investigate the effect of blending,finding that any sources with separations smaller than the beam size are fit assingle sources. We show that the use of machine-learning techniques cancorrectly identify blended sources up to 90 per cent of the time, andprior-driven fitting can lead to a 70 per cent improvement in the number ofde-blended sources.

Deep 3 GHz Observations of the Lockman Hole North with the Very Large Array - 1. Source extraction and uncertainty analysis