  NRAO Very Long Baseline Array (VLBA) observations of NGC 4278, NGC 4374
(M84), NGC 6166, and M87 (NGC 4486) have been made at 43 GHz in an effort to
image the jet collimation region. This is the first attempt to image the first
three sources at 43 GHz using Very Long Baseline Interferometry (VLBI)
techniques. These three sources were chosen because their estimated black hole
mass and distance implied a Schwarzschild radius with large angular size,
giving hope that the jet collimation regions could be studied. Phase
referencing was utilize for the three sources because of their expected low
flux densities. M87 was chosen as the calibrator for NGC 4374 because it
satisfied the phase referencing requirements: nearby to the source and
sufficiently strong. Having observed M87 for a long integration time, we have
detected its sub-parsec jet, allowing us to confirm previous high resolution
observations made by Junor, Biretta & Livio, who have indicated that a wide
opening angle was seen near the base of the jet. Phase referencing successfully
improved our image sensitivity, yielding detections and providing accurate
positions for NGC 4278, NGC 4374 and NGC 6166. These sources are point
dominated, but show suggestions of extended structure in the direction of the
large-scale jets. However, higher sensitivity will be required to study their
sub-parsec jet structure.
