Quote:
Originally Posted by PJH
I haven't ventured into Sat/ISS stuff other than the 2M downlinks for ham, but I just curious if there is anything left "in the clear" that could be received with a basic scanner and external antenna. I know most STS and ISS stuff is done via links (L/S band?), but HF, VHF, UHF with a plain old Uniden?
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Yes, there's still some non-secure, analog voice UHF SATCOM stuff out there. It's somewhat rare compared to 10 or 20 years ago because the JCS required FLTSATCOM users to go from analog voice (with or without digital encryption) to a mode called Demand Assigned Multiple Access (DAMA) to improve spectrum/power efficiency.
Seems like a lot of the Space Shuttle liftoff/recovery nets are still heard in analog, non-secure mode, as well as some special ops aircraft operations in the Iraq/Afghanistan areas for some reason. You'll also occasional hear the pesky cheap-bastards bootlegging on UHF SATCOM.
Sometimes, some analog, non-secure operations overheard are thought to be co-channel interference from assets unknowingly using the same freq as a FLTSATCOM transponder uplink but the reality is the localized tactical comms are intentionally being retrans'ed via UHF SATCOM so that staff in command centers or operators on inbound aircraft can monitor the activity. In other cases, it's just been poor frequency planning.
Check the 244MHz for the AFSATCOM downlinks (sounds like RTTY). 250s is mostly Navy tactical digital information exchange ("TADIX") nets, intel agency covert sensor relays, etc. & I think the 260s is where you'd still heard most voice activity here in the USA -- both tactical stuff as well as strategic nets, such as NORAD/NORTHCOM Net A, National Command Authority wideband, etc.
A lot of cool stuff once taking place via the UHF FLTSATCOM birds have jumped over to Inmarsat & other commercial/military SATCOM systems over the past 10 years or so. Monitors in the right part of the world used to be able to hear the Joint Task Force - Full Accounting missions into Vietnam & even North Korea on clear-voice UHF SATCOM (& HF) because as part of the host-nation requirements to enter the country, no secure communications were permitted. That was OK, because especially with a phucked-up nation like N Korea, we didn't want to take any controlled cryptographic items into the county anyway.
Back in the early 1980s I was able to QSL one of the US research stations in the South Pole using a decaying LES-9 satellite UHF transponder that no longer met military requirements. I'll never forget hearing the phone patch on it between a guy in Antarctica & his wife in CONUS. She asked him if he was in a good mode, told him to sit down, and then she told him she was pregnant. I was too young & naive at the time to wonder if he'd been away from her in Antarctica for the past 9+ months or not, but the fact that an 11th-grader radio geek in Michigan was able to listen in on that sort of highly-personal conversation taking place between a wife in California & a husband near the South Pole over a military satellite was rather surreal...
I also QSL'ed the historic 1986 around the world flight of Voyager on UHF SATCOM -- DOD granted them special access.
Technology is such these days that a person with a handheld radio & special omni-directional looking antenna can access FLTSATCOM.
Whether or not you decide there's enough analog, clear-voice activity to make it worth it to improve your chances of hearing UHF SATCOM by getting a right-hand circularly polarized or cross-polarized antenna and a good preamp centered on about 260MHz is up to you...
/-/ooligan
Longtime UHF SATCOM monitor, former UHF SATCOM customer
Anything "in the clear"?
Linear Mode
