In particular, many Pacific transponders frequently pick up signals from Russian mobile telephone base stations. The satellites over Asia, on the other hand, do not appear to carry much pirate traffic but suffer from a large number of legitimate terrestrial signals on the uplink frequencies that make it into the satellites and that are relayed on the downlink. In South America - principally Brazil - a large community of "pirate" users have discovered ways to modify VHF amateur radio gear to access the SATCOM system, and their signals comprise the vast majority of the clear traffic going through the transponders that cover the Americas.
There are a number of unauthorized and unintentional signals as well, which vary by region. Most military traffic is digitally encrypted, but there are occasional analog clear transmissions as well, usually in FM mode (the transponders will pass almost any modulation that fits within their passband).īut military messages are not the only transmissions that pass through the TACSAT transponders.
#SATELITE DOWNLINK PORTABLE#
This system is used by ground troops, typically employing portable "manpack" transceivers and lightweight tripod-mounted antennas, as well as by aircraft and ships when they travel outside of HF and VHF line-of-sight range. UHF military satellites are used chiefly to support the low bandwidth voice and data TACSAT system. Some samples of the spectrum produced by various transponders can be found here. The focus is on geostationary downlinks (which can be received over a large footprint and without the need to calculate their position based on time), but non-geostationary LEO, MEO, and HEO transponders will be included if I happen to catch them. This page lists the UHF satellite signals that I can receive and measure with my own (limited) equipment at several (sub-optimal) receiving sites on the East and West coasts of the US. So I've set about cataloging the downlink signals between 243 and 270 MHz that can be easily and regularly received in North America. That list UHF military satellite downlinks, but most of them, for whatever reason, are focused on signals that can be received in Europe. I've found a number of excellent web resources (such as and ) UHF SATCOM Satellite Downlinks Receivable in North America UHF SATCOM Downlinks Receivable in North America
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