  The KVN(Korean VLBI Network)-style simultaneous multi-frequency receiving
mode is demonstrated to be promising for mm-VLBI observations. Recently, other
Very long baseline interferometry (VLBI) facilities all over the globe start to
implement compatible optics systems. Simultaneous dual/multi-frequency VLBI
observations at mm wavelengths with international baselines are thus possible.
In this paper, we present the results from the first successful simultaneous
22/43 GHz dual-frequency observation with KaVA(KVN and VERA array), including
images and astrometric results. Our analysis shows that the newly implemented
simultaneous receiving system has brought a significant extension of the
coherence time of the 43 GHz visibility phases along the international
baselines. The astrometric results obtained with KaVA are consistent with those
obtained with the independent analysis of the KVN data. Our results thus
confirm the good performance of the simultaneous receiving systems for the
non-KVN stations. Future simultaneous observations with more global stations
bring even higher sensitivity and micro-arcsecond level astrometric
measurements of the targets.
