L-Band (1600-1700MHz) Survey Spectrum Notes

The OH spectrum is dominated by the Iridium/Globalstar uplink/downlinks, covering the band 1610-1626MHz, and are present in every direction. The levels on these transmissions do vary, however, it is safe to assume, that they are of a continuous transmission. There is also an ever present Glonass transmission, covering the band 1602-1615MHz, however, it is highly variable, and is generally, much weaker than the Iridium/Globalstar transmissions.
There are a series of unlicensed transmissions (not listed in ACA database), from the east, at 1681MHz, 1686MHz, and at 1691MHz. These transmissions are of a continuous nature. They appear in other views (much less), the signal presence being attributed to the fact, that at the moment, the RFI monitoring tower is within close proximity to the Kennedy 60' telescope, and hence, some reflected transmissions are likely being picked, notably in western views (NB The RFI monitoring tower is to the east of the main observatory, and just east of the Kennedy 60' telescope).
A small signature at 1664MHz, when viewed west is attributed to the 13th harmonic of the 128MHz sampler clocks, used at the observatory (NB the 11th harmonic is also seen at 1408MHz), and there is a small signature at 1604MHz, source unknown, probably from the observatory.
In the northern view, there are brief RFI signatures at 1647.7MHz, and 1657.9MHz, of which, their existance in the survey lasted only 16 integrations and 7 integrations respectively, and remain in the averaged spectrum plots, from which, there are typically 50 integrations averaged.