In this paper we present the results of a survey for radio transients using data obtained from the Very Large Array archive .
We have reduced , using a pipeline procedure , 5037 observations of the most common pointings – i.e .
the calibrator fields .
These fields typically contain a relatively bright point source and are used to calibrate ‘ target ’ observations : they are therefore rarely imaged themselves .
The observations used span a time range \sim 1984 – 2008 and consist of eight different pointings , three different frequencies ( 8.4 , 4.8 and 1.4 GHz ) and have a total observing time of 435 hours .
We have searched for transient and variable radio sources within these observations using components from the prototype LOFAR transient detection system .
In this paper we present the methodology for reducing large volumes of Very Large Array data ; and we also present a brief overview of the prototype LOFAR transient detection algorithms .
No radio transients were detected in this survey , therefore we place an upper limit on the snapshot rate of GHz frequency transients > 8.0 mJy to \rho \leq 0.032 deg ^ { -2 } that have typical timescales 4.3 to 45.3 days .
We compare and contrast our upper limit with the snapshot rates – derived from either detections or non-detections of transient and variable radio sources – reported in the literature .
When compared with the current Log N – Log S distribution formed from previous surveys , we show that our upper limit is consistent with the observed population .
Current and future radio transient surveys will hopefully further constrain these statistics , and potentially discover dominant transient source populations .
In this paper we also briefly explore the current transient commissioning observations with LOFAR , and the impact they will make on the field .