ISS Cross Band Repeater

fyffer

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https://amsat-uk.org/2020/09/02/iss-fm-repeater-activated/

The cross band repeater on the space station is now operational.
So I am reading quite a bit about APRS and just got done reading an interesting blog, by a man named Blargh from April 20, 2020. He states " you can bounce messages off of the ISS. It has a digipeater. It’s not on the standard APRS frequency, but on 145.825 MHz. This way you can reach really far in one hop."

NOTE WORTHY though, he has not tried it. I tried to copy the link but failed.

I'll figure I better ask a Guru, as I am extremely new to the HAM world. Could it be useful or discouraged.

Do you know anything about this Dave. ?
 

DaveInDenver

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All spaceborne APRS is done on 145.825, not just ISS. Although the space station is the most targeted APRS digipeater if you're trying to make contacts.

http://www.aprs.org/pcsat.html

APRS in space can be used like terrestrial (we use 144.390 here in the U.S.) but being a different RF network it's not a seamless extension. There's no APRS-IS gateway for the ISS so packets don't make it to the Internet in the regular places like aprs.fi or the SMSGTE.

I don't know of any reason there couldn't be an iGate for 145.825, I guess no one has bothered is all. It wouldn't be useful unless both you and the iGate can see the ISS at the same time, though. So there'd have to be a lot of iGates around the globe to make it useful like regular APRS.

You can see if the ISS heard you, though: http://www.ariss.net/
 

3rdGen4R

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Sounds like you can setup a ADHOC network using ISS. I wonder how much bandwidth that ISS can receive and transmit. If it can do enough maybe you can establish the network somewhere on earth instead of the ISS. Either way I find this interesting.
 

DaveInDenver

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BTW, the cross-band repeater is a voice repeater, not APRS. You talk in on 145.990 (with PL 67Hz) and listen on 437.800. There's other voice amateur satellites. I've dabbled in making contacts but it's not something I can claim a lot of personal experience. What I've done of it has been with an dual band/dual VFO HT and handheld Yagi.

https://www.amsat.org/

The APRS segment of the ISS is a different system.
Sounds like you can setup a ADHOC network using ISS. I wonder how much bandwidth that ISS can receive and transmit. If it can do enough maybe you can establish the network somewhere on earth instead of the ISS. Either way I find this interesting.
We don't really have an APRS 101 thread, although Marco and TJ started threads that kind of serve as that.


APRS is something a few in the club have but only a few of us do any more than beaconing positions. It's much more than just that, two-way messaging, weather reporting objects, broadcast messages, station telemetry or status, there's also an SMS gateway and an email gateway, etc.

We have Bob Bruninga, WB4APR, to thank for APRS itself.

http://www.aprs.org

Basically APRS is ad-hoc, stations may join and leave at will, that greatly favors short data burst (the largest frame is around 328 bytes, AX.25 formatted carried over the via simple Bell 202 modem) for wide area information exchange over sustained simplex or BBS type communication that's traditional packet radio.

The APRS on the ISS is a subset APRS network. It doesn't interact with the regular APRS network because the nature of an ISS repeater would end up being swamped. It would might have thousands of stations trying to fight for slots, each filling its 1200 baud link with 250 ms packets. As it is some of main top tier dipeaters in Denver are at 100% duty cycle most of the day and they're only covering a few square miles with a handful of lower dipeaters. The ISS APRS dipeater has a footprint so much larger, it would a real charlie-foxtrot.

The bandwidth limit is in the FCC rules. For 2m we're hard limited to 19.2 kbaud (symbol rate). On 70cm we can do 56 kbaud. The APRS VHF link on the ISS can do 1200 baud (this is typical for the AFSK modems we use for APRS) and for the most part 9600 baud is the practical limit on 70cm. In theory if someone wanted to build an v.34 or OFDM repeater for an AMSAT we could do pretty decent bitrates, although doing so over the air with Doppler shift isn't easy. The FCC rules allow up to 100KHz bandwidth on 70cm, for example, so that would be our limit. Even 9600 baud AFSK on terrestrial 70cm can be difficult. It's of course 100% doable.
 
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DaveInDenver

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This statement in the v1.1 spec addendum sums up the intention of APRS.

APRS is NOT Ham Radio's MOBILE COMPUTING:
The 1200 baud national APRS user channel cannot and was never intended to be Ham Radio's solution to Mobile Computing. The thousand-fold greater bandwidths required for typical Mobile Computing applications are enormous and there is no attempt to clutter the APRS channel with all possible data that might be of use to a user with a laptop in his car. APRS is for brief, short data types of immediate Ham Radio interest to all tactical users on the local RF channel.
 

3rdGen4R

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This statement in the v1.1 spec addendum sums up the intention of APRS.
While it is not a mobile computing solution, one can't help but see that the fact you can send email, receive messages, transmit pictures, compress date, uncompress data, and so on and on and on... is kind of self defeating as I know people that have really gotten into ARPS have done all of these things. And it's using some of the same topologies of networks, even with data transmission. I see your point, but it seems like people are trying to do this kind of stuff with ARPS.
 

DaveInDenver

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While it is not a mobile computing solution, one can't help but see that the fact you can send email, receive messages, transmit pictures, compress date, uncompress data, and so on and on and on... is kind of self defeating as I know people that have really gotten into ARPS have done all of these things. And it's using some of the same topologies of networks, even with data transmission. I see your point, but it seems like people are trying to do this kind of stuff with ARPS.
Completely agree about email pushing the limits even without attachments. APRS messages are a fundamental part of the spec and the SMS gateway only needs an extra 10 characters (the recipient's digits or alias if you've assigned one) beyond a regular APRS message so it's not a great deal of overhead. The nature of APRS doesn't lend itself to sustained data like that since the clients aren't expecting to recover multiple packets per message.

I think the spec writers' point is to be mindful that the topology isn't a substitute for true data networks, at least on VHF. We have so little spectrum on 2m it has to be used efficiently. All the high bandwidth stuff is done on UHF where the Internet is extended to long distances on ham bands. None of it is flying though, just terrestrial.


You might find AREDN Mesh interesting (this primarily uses repurposed WLAN gear) and the other HamNet/HSMM mesh networks. One of the primary drivers for this is ARES and other EMCOMM support functions.
https://www.arednmesh.org/
https://hotarc.org/mesh/
https://hamwan.org/

I have a couple of old WRT54 routers that I flashed with HSMM-Mesh firmware to extend the network to north Loveland years ago but they dropped support for that ancient stuff so I haven't done anything about it here with newer hardware.


Or the New Packet Radio experimentation.
https://hackaday.io/project/164092-npr-new-packet-radio
https://spectrum.ieee.org/geek-life/hands-on/build-a-longdistance-data-network-using-ham-radio

This is intriguing but I've only read about it so to call it a cursory awareness is generous. In the original configuration it exceeded our bandwidth limits in the U.S. but I think that's been addressed now.


And TARPN
http://tarpn.net/t/packet_radio_networking.html

I've built a couple NinoTNCs but I don't have a radio that's been much good at 9600 so haven't really done much with TARPN yet.


So many things to tinker with, so little time and money!
 
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