The mean absolute brightness temperature of the diffuse radio background was measured as a function of frequency in a continuous band between 100 and 200 MHz over an effective solid angle of \sim \pi str at high Galactic latitude .
A spectral brightness temperature index of \beta = 2.5 \pm { 0.1 } ( \alpha _ { S } = 0.5 ) was derived from the observations , where the error limits are 3 \sigma and include estimates of the instrumental systematics .
Zenith drift scans with central declination \delta = -26.5 ^ { \circ } and spanning right ascensions 0 < \alpha < 10 h yielded little variation in the mean spectral index .
The mean absolute brightness temperature at \nu = 150 MHz was found to reach a minimum of T = 237 \pm { 10 } K at \alpha = 2.5 h. Combining these measurements with those of yields a spectral index of \beta = 2.52 \pm { 0.04 } between 150 < \nu < 408 MHz .