One of the first things that an amateur radio operator is likely to do once receiving their license is grab a dual-band handheld and try to make contacts with a local repeater. After the initial contacts, though, many hams move on to more technically challenging aspects of the hobby. One of those being activating space-based repeaters instead of their terrestrial counterparts. [saveitforparts] takes a look at some more esoteric uses of these radio systems in his latest video.
There are plenty of satellite repeaters flying around the world that are actually legal for hams to use, with most being in low-Earth orbit and making quick passes at predictable times. But there are others, generally operated by the world’s militaries, that are in higher geostationary orbits which allows them to serve a specific area continually. With a specialized three-dimensional Yagi-Uda antenna on loan, [saveitforparts] listens in on some of these signals. Some of it is presumably encrypted military activity, but there’s also some pirate radio and state propaganda stations.
There are a few other types of radio repeaters operating out in space as well, and not all of them are in geostationary orbit. Turning the antenna to the north, [saveitforparts] finds a few Russian satellites in an orbit specifically designed to provide polar regions with a similar radio service. These sometimes will overlap with terrestrial radio like TV or air traffic control and happily repeat them at brief intervals.
[saveitforparts] has plenty of videos looking at other satellite communications, including grabbing images from Russian weather satellites, using leftover junk to grab weather data from geostationary orbit, and accessing the Internet via satellite with 80s-era technology.
I’m assuming these are old satellites, and that a modern military communication device would have a mechanism to prevent it from repeating pirate radio or civilian tv? I.E. a digital signal with authentication?
Kind of wild that there was a time when you could chuck something into space without worrying about access controls.
Great question. I heard people (here) making the case that the military ones would simply repeat, and let the encryption happen at the endpoints rather than having encryption on the thing in space, heaven forbid the encryption is broken on something that’s completely inaccessible.
Usually if radio is encrypted its done at the transceiver
Repeater will just typically take whatever it’s sent and retransmit on a different frequency or band
They can include something called pl tones a low frequency tone to “authenticate” to a repeater that’s the transceiver signal is valid and key the repeater
Pl tone or ctcss is basically a low sub 300hz inaudible tone or carrier superimposed on the existing rf signal, normally used on repeaters or radios that operate near the same frequency and are close enough to possibly key each other. It only will activate if the pl tone is correct.
you could increase the frequency a little and modulate some digital data such as a rolling code of sorts to add security from a civilian transceiver, don’t need that much bandwidth to send encryption handshake or keys….
Also use a non standard ctcss tone
Here in Germany/Europe we historically had 1750 Hz tone for opening the FM relays, too.
Unfortunately, the CTCSS was being forced upon us in the past ~15 years.
Because, US and Japan.. They’re cool, after all. So we must obey. They’re leading ham radio, after all.
The result is now that a lot of vintage radios in our place can nolonger be used on the FM relays.
These excellent, true-FM radios (no PM, but FM) could have been passed on to the next ham generation.
Adding CTCSS support is tricky, because Mic amp must be by-passed (it filters low signals).
On bright side, many repeaters now drop CTCSS and 1750 Hz and use carrier detection.
Primitive and prone to interference, but what else can you do about it? 😟