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We present the analysis results of the simultaneous multifrequencyobservations of the blazar 4C +28.07. The observations were conducted by theInterferometric Monitoring of Gamma-ray Bright Active Galactic Nuclei (iMOGABA)program, which is a key science program of the Korean Very Long BaselineInterferometry (VLBI) Network (KVN). Observations of the iMOGABA program for 4C+28.07 were conducted from 16 January 2013 (MJD 56308) to 13 March 2020 (MJD58921). We also used {\gamma}-ray data from the Fermi Large Array Telescope(Fermi-LAT) Light Curve Repository. We divided the iMOGABA data and theFermi-LAT data into five periods from 0 to 4, according to the prosody of the22 GHz data and the presence or absence of the data. In order to investigatethe characteristics of each period, the light curves were plotted and compared.However, a peak was observed earlier than the period of a strong {\gamma}-rayflare at 43-86 GHz in period 3 (MJD 57400-58100). Therefore, we assumed thatthe minimum total CLEANed flux density for each frequency was quiescent flux(Sq), with the variable flux (Svar) obtained by subtracting Sq from the valuesof the total CLEANed flux density. We then compared the variability of thespectral indices ({\alpha}) between adjacent frequencies. Most notably,{\alpha}22-43 showed optically thick spectra in the absence of a strong{\gamma}-ray flare, and when the flare appeared, {\alpha}22-43 became opticallythinner. In order to find out the characteristics of the magnetic field in thevariable region, the magnetic field strength in the synchrotron self-absorption(BSSA) and the equipartition magnetic field strength (Beq) were obtained. Wefound that BSSA is largely consistent with Beq within the uncertainty, implyingthat the SSA region in the source is not significantly deviated from theequipartition condition in the {\gamma}-ray quiescent periods.

Interferometric Monitoring of Gamma-ray Bright AGNs: 4C +28.07 and its Synchrotron Self-absorption Spectrum