[amsat-bb] How to digipeat?

[Hans BX2ABT]

Hello Scott,

Thank you so much for writing this long reply. We should archive it for 
future use, because this is very comprehensive.

Just by trying many options I was able to get UISS to send something out 
on Falconsat-3. I tried CQ, ARISS, and BEACON and used the FPS3-1 as 
path. Half an hour later on Twitter I received a notification from 
E29AHU in Thailand that he saw my digipeat on his soundmodem output. 
There are some tweets on Twitter with screenshots, so just search for 
BX2ABT. So a little success and at least I know UISS is working.

Unfortunately, if this whole digipeating means there is no 
store-and-forward and you need iGates to be able to see your digipeats 
on the web then I won't have much fun with this, because here in east 
Asia it is very quiet. There were some JA hams working the FS-3 BBS and 
also digipeating, but they have been inactive lately. Maybe I can 
persuade them to do some experimenting with me.

73 de Hans

BX2ABT


On 09/08/2019 04:35 AM, Scott via AMSAT-BB wrote:
> Hi Hans!
>
> Like any digital mode, 1200 or 9600 packet requires several things to work
> together using the correct settings.  This might run a little long, but
> I'll be glad to outline them.
>
> But first, one helpful thing to remember is that you want to treat the
> uplink & downlink as completely separate affairs.  Depending on the
> satellite, the uplink and downlink might find you using different bands,
> different radios, different antennas, different software... at a MINIMUM
> you'll be using different RF frequencies even if it's a simplex packet
> digipeater since the doppler compensation will be opposite for up -vs-
> down. (caveat - on 2m normal FM you can get by with sitting on one freq)
>   To me it's always made sense to verify that you're 100% good to go on the
> downlink, then set yourself up for the uplink.
>
> So, if anyone wants to read on, here are the things to consider.
>
> RF:  you'll need to know what the uplink & downlink RF frequencies are and
> if either is in the 70cm band, doppler compensation is mandatory.  Here's a
> tip: several of the newer sats are using NARROW-FM... even if you're
> working on 2 meters, doppler compensation to/from a narrow-band satellite
> radio is making a huge difference in my experience.  CAT control your radio
> if possible; if not, then pre-program 5 memory channels the way most people
> have their FM radios setup for voice satellite work.
>
> MOD/DEMOD:  your radio needs to have a connection to your computer where
> you run software set to decode the type of modulation in use by the
> satellite.  On Windows, the various UZ7HO Soundmodem versions provide
> perhaps the easiest interface to work with.  Direwolf is an option on
> Windows, too, and by-the-way makes for a very easy to use iGate utility
> running off to the side of your screen.  On linux, Direwolf is the most
> popular option to my knowledge.  On either platform, of course we have to
> find out from the satellite documentation what settings are required.  A
> critical note that often prevents success on rates above 1200 baud is that
> beyond that speed we need more audio bandwidth than is normally available
> for general listening.  So, whether you're using a "real" radio or an SDR,
> good rules of thumb are 3KHz of audio bandwidth for 1200 baud and 15KHz of
> audio bandwidth for the higher rates.  On modern radios, that means using a
> connection to the radio's "DATA" port for rates above 1200.  My TM-V71A,
> for example, also has a menu option to switch between 1200 & 9600 - very
> important!
>
> USER INTERFACE:  as you mentioned, the UISS software is a great tool to use
> as the interface when sending/receiving the packet modes.  It communicates
> with UZ7HO Soundmodem or Direwolf to send/receive data to/from the
> satellite.  But what to transmit?  We need that info from the satellite
> documentation.  The "TO" is most often "CQ", but read everything you can
> find about the satellite in question to be sure. (hint: monitor the
> downlink & see what others are using!)  The "VIA" can be confusing because
> many sats will respond to more than one name.  It all comes down to the
> documentation - historically the 1200 baud APRS sats will answer to "ARISS"
> which is handy... you don't have to change all your settings between
> satellites.  FalconSat-3 is different; we use "PFS3-1" when transmitting to
> FS-3.  "If" there actually is an active digipeater on BugSat-1, the team
> has instructed us to use "LU7AA" as the call sign to access that satellite.
> (I've tried BugSat-1 twice now but at the time of this post, have not had
> any success)  As for the payload text to transmit, UISS helps a lot (for
> APRS sats) by guiding us into sending properly formatted 'TEXT',
> 'POSITION', and 'MESSAGE' type APRS packets.  Monitoring the downlink and
> seeing what message types others are having success with is helpful here.
> Heck, everything I do on the sats is a copy-cat of the operating techniques
> used by the operators that you see post repeatedly here, on Twitter,
> QRZ.com, and elsewhere.   A huge 'thank-you' to all who share how-to info!
>
> So, aside from individual considerations that are unique to particular
> satellites (FS-3 is cross-band full-duplex, for example), that is an
> overview.  If anyone has read this far, you have my sympathy.  I just
> wanted to spell out what is common knowledge to most here on the chance
> that one item might ring a bell and answer a question for you.  If the ISS
> or either of the PSAT digipeaters would come back online, that would make
> it a lot easier to practice with these modes.  As of the date I'm typing
> this, all we have active over my location in the U.S.  are AISAT-1 (1200
> narrow-FM) & FS-3 (9600).
>
> Good luck!
>
> -Scott,  K4KDR
>
> ===========================
>
> On Sat, Sep 7, 2019 at 11:01 AM Hans BX2ABT via AMSAT-BB <amsat-bb at amsat.org>
> wrote:
>
>> Hello all,
>>
>> Apparently my mail about BugSat-1 raised some interest into that bird's
>> digipeater. But that still leaves me with the following question (and I
>> hope I don't sound too obtuse): how do you digipeat? I've tried to
>> understand it by googling it over the past year or so, but I still don't
>> get it much. Most tutorials explain about setting it up, but with HTs. I
>> am running a home station only, with the rig connected to a PC. From
>> what I understand you need to use the program UISS then.
>>
>> I got as far as this: I installed UISS (under Wine) and got it connected
>> to Direwolf. Right now I can work the Falconsat-3 BBS using PacSat
>> Ground Station and while running that program I see the same messages
>> that Direwolf displays also appearing in UISS. So far, so good, but then
>> what? I press either F5, F6, or F7, but nothing happens. Yes, my rig
>> burps out some data for a split second, but I can't find myself back on
>> APRS.fi. So what am I doing wrong? Any parameters to adjust? Or are
>> digipeats not stored for the next iGate to put it on the internet?
>>
>> Again, I hope I don't sound too witless, but I've never really
>> understood APRS, apart from terrestrial position reporting and even that
>> was kind of hard with all the paths and whatnot. Hope you nice people on
>> this list can drop some pointers. 73 de Hans
>>
>> P.S. I've got some nasty local interference on 145.825 MHz and that
>> makes receiving the ISS and other birds almost impossible. I was lucky
>> to get two frames in from IO-86 the other day, because that was due
>> south, with the QRM coming from the north-east. Getting a signal up
>> shouldn't be much of a problem, though.
>>
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