We determined the separations of the radio sources in the triangle formed by the BL Lac objects 1803+784 and 2007+777 , and the QSO 1928+738 from intercontinental interferometric observations carried out in November 1991 at the frequencies of 2.3 and 8.4 GHz simultaneously .
Difference phase-delay astrometry yielded the following separations :
[Table Here]
We successfully connected differenced phase delays over 7 ^ { \circ } on the sky at 8.4 GHz at an epoch of maximum solar activity .
The effects of the ionosphere on these VLBI data were mostly removed by estimates of the total electron content from observations of GPS satellites .
The comparison of the estimated separation of QSO 1928+738 and BL 2007+777 with previous such estimates obtained from data at different epochs leads us to a particular alignment of the maps of QSO 1928+738 at different epochs relative to those of BL 2007+777 , although with significant uncertainty .
For this alignment , the jet components of QSO 1928+738 show a mean proper motion of 0.32 \pm 0.10 mas/yr and also suggest an identification for the position of the core of this radio source .