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? 😟
A number of MilSats were just geostationary bentpipes. with no access control. wide and narrow channel UHF repeaters, but comms were mostly encrypted (except for maintenance and testing. All you needed was the freqs , radios, and sat antenna and you could hit them.
The intermediate Ham band referenced @4:20 is the 1.25m band from 222-225 MHz and an allocation at 219-220 MHz for fixed digital messaging forwarding systems only.
It is less used than 2m or 70 cm but saying that almost no one uses it is an overstatement.
73
KR4AHM
It doesn’t really exist as ham band in Europe/IARU Region 1, though.
To us, it’s a very strange niche band. Most hams here have never heard of it.
Merely some SWLs may listen to it, sometimes.
“It is not available for use in ITU Region 1 (except in Somalia) or ITU Region 3”
Source: https://en.wikipedia.org/wiki/1.25-meter_band
vy73s,
Reminds me of when I heard about the ISS repeater – I was surprised. I got it set in such a way that it updates the position of that repeater on the site I manage, in the list of repeaters : https://hearham.com/repeaters/?s=NA1SS
Might be the only entry of a repeater that regularly moves? :)
Listening to ISS is fun.
Just use an RTL SDR for reception, or an old FM scanner (Uniden etc).
If it has older 25 KHz raster, then that’s fine. The wider, the better.
Using a basic groundplane or Helix antenna is recommended.
Correction for doppler effect is nice extra, but Packet-Radio with FSK is quite robust.
Modern SDR programs can keep locking on a signal, too,
and modern SSTV programs can be compensating for a slow frequency drift so it’s not that critical.
You can use Heavens Above for tracking, for example.
The website or the Android application (can run on android TVs, BD players etc).
A friend uses the classic, STS Orbit +, by the way.
An DOS program from the 90s that flew on MIR and simulates Nasa Mission Control (can be found at Celestrak).
For SSTV reception, PD-120 is being used (MIR had used Robot 36).
On Mac, Multimode works quite good. On Windows, MixW2/MixW3 is worth a try.
On Linux, you can try QSSTV for decoding.
For APRS decoding, UI-View and Xastir can be used.
Xastir uses vector maps and runs on Linux mainly (or any other *nix).
UI-View is for Windows, uses bitmaps as maps and has templates for several classic TNCs,
but can also be fed with data of a KISS TNC (DireWolf, Soundmodem, MixW virtual Packet-Radio TNC).
A null-modem must be used to connect the applications (real or virtual).
UI-View 16-Bit is Freeware, UI-View 32-Bit needs a registration (free, doesn’t hurt).
The 16-Bit version still runs in DOSBox+Windows 3.1 or on 32-Bit Windows (Windows 98SE, XP etc) and on OS/2 (incl ArcaOS etc).
It’s really lightweight, too, so an old laptop with TNC can be used.
Anything that runs Windows 3.1x in short (even an 80286 PC with 4 MB of RAM).
Last but not least, there’s also MacAPRS.
It still works on older Macintoshs, such as Power Macs.
Here it needs Mac OS 8/9, but a last version compatible with Mac OS X exists, as well.
So Mac OS X up to 10.6.8 can run it (via Rosetta).
Maybe cool for vintage Mac fans, also makes a good addition to any ham shack!
Early versions run on System 7 Macs, such as Quadra, LCs or the Mac Classic.
Originally, there was that cycler with a mobile SSTV station using an 68k Mac..
vy73s