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We present the results of comparative study of amplitude calibrations forEast-Asia VLBI Network (EAVN) at 22 and 43 GHz using two different methods ofan "a-priori" and a "template spectrum", particularly on lower declinationsources. Using observational data sets of early EAVN observations, weinvestigated the elevation-dependence of the gain values at seven stations ofthe KaVA (KVN and VERA Array) and three additional telescopes in Japan(Takahagi 32m, Yamaguchi 32m and Nobeyama 45m). By comparing the independentlyobtained gain values based on these two methods, we found that the gain valuesfrom each method were consistent within 10% at elevations higher than 10degree. We also found that the total flux densities of two images produced fromthe different amplitude calibrations were in agreement within 10% at both 22and 43 GHz. By using the template spectrum method, furthermore, the additionalradio telescopes can participate in the KaVA (i.e. EAVN) so that it can give anotable sensitivity increase. Therefore, our results will constrain thedetailed conditions to reliably measure the VLBI amplitude using EAVN and givea potential to extend possible telescopes comprising EAVN.

A comparative study of amplitude calibrations for East-Asia VLBI Network: a-priori and template spectrum methods