We combine surveys of the radio sky at frequencies 22 MHz to 1.4 GHz with data from the ARCADE-2 instrument at frequencies 3 to 10 GHz to characterize the frequency spectrum of diffuse synchrotron emission in the Galaxy .
The radio spectrum steepens with frequency from 22 MHz to 10 GHz .
The projected spectral index at 23 GHz derived from the low-frequency data agrees well with independent measurements using only data at frequencies 23 GHz and above .
Comparing the spectral index at 23 GHz to the value from previously published analyses allows extension of the model to higher frequencies .
The combined data are consistent with a power-law index \beta = -2.64 \pm 0.03 at 0.31 GHz , steepening by an amount \Delta \beta = 0.07 every octave in frequency .
Comparison of the radio data to models including the cosmic ray energy spectrum suggests that any break in the synchrotron spectrum must occur at frequencies above 23 GHz .