[amsat-bb] Falconsat-3 - The APRS satellite for Mobiles (h-dux TNC)

[Jim White]

Bob,

A digipeated packet received on the uplink will get repeated immediately 
upon the receipt of the last byte, unless delayed by a few ms by other 
processing going on or other packets queued to be sent.

If there is nothing cued in the downlink already the repeated packet 
will be sent on the downink starting a few ms after that last uplink 
byte is received.  If there are other packets (telemetry, BBS traffic, 
status messages, etc.) in the output queue the digipeated packet will be 
queued at the end of those other packets.  For example if a file 
download is in progress the digipeated packet will be inserted between 
file packets because the file packets are queued into the downlink 
processing one packet at a time.  It's theoretically possible for a 
digipeated packet to be queued for a couple of seconds, but that's not 
likely the way the satellite is currently being used.

Jim

On 2/20/2019 3:28 PM, Robert Bruninga wrote:
> Yes, all of kenwood TNC’s do not operate full duplex even though the radio
> does full duplex crossband…  In other words, it cannot decode a packet while
> it is transmitting one.  But the Falconsat downlink is fulldupelex and it
> can begin including a downlink packet in the downlink stream even before the
> uplink is finished.  (or at least, there is no TXD delay, and so the user
> TNC on receive does not hear the start of the packet in most cases, unless
> the downlink packet happens to be delayed in the stream due to other
> Falconsat BBS data.
>
> I hope I got that right...
> Bob, WB4APR
>
>> regarding the TNC NOT operating full duplex...
>> is this true in, say, the TH-D72A as well?
>> that explains a LOT about the behavior I've seen using it,
>>   and guess I'd need to go to a full 2 radio solution
>> to see my packets digipeated?
> On Wednesday, February 20, 2019, 2:10:03 PM EST, Robert Bruninga
> <mailto:bruninga at usna.edu> wrote:
>
> Work a satellite from your APRS mobile, 5 times a day:
>
> For APRS folks just sittin in their mobile with nothing to do, you can work
> FALCONSAT from any APRS Mobile…  Just confirm passes using Heavens-above.com
> (be sure to enter your location).  Though passes now are from about midnight
> to 6 AM, that pattern moves earlier about 36 minutes a day so it
> will be in the evenings in a few days.
>
> The Falconsat digipeater operates APRS at 9600 baud and works fine from a
> 50W APRS mobile with mobile antenna.  Just turn on your rig, set the
> internal TNC to 9600 baud and monitor the downlink.  You should see packets
> from PFS3-1 and or other stations.
>
> Tune 435.110 MHz at start of pass, then clicking down steps of 5 Khz towards
> the middle of the pass and then ending at 435.095 by the end ten minutes
> later.  If you are just going to monitor overnight, set to 435.105 for the
> early middle of the pass and check your LIST in the morning.
>
> Uplink takes a bit more settings.  Set your PATH to go via PFS3-1 and set
> TNC to TX A and  RX B and set uplink on band A to 145.84 (no need to step
> doppler).  Set beacon to once a minute (and turn off decay and Proportioinal
> pathing).  You will NOT see your own digipeats.  Although the satellite and
> D710 are operating full duplex, the D710 TNC is not.  By the time the TNC
> TX/RX turns around, you will already have missed it.  So don’t just keep
> TXing until success,  You WONT see it.  But when you DO see someone else
> doing APRS, then by all means send them a message.  If he ACKS, then
> success!
>
> I just did the math.  You don’t even need no stinkin computer.  Once  you
> hear a pass, then just remember that passes are 36 minutes earlier each day
> and the next pass on any given day is 98 minutes later (unless that was the
> last pass of the day).  During a western trip, just jotting down the time of
> a pass heard, then I could predict pass times therest of the day and every
> day for weeks.  Always just adding 98 minuets to the next pass and listening
> 36 minutes earlier each day.  See this manual technique:
> http://aprs.org/MobileLEOtracking.html
>
> Here is how WD9EWK describes working FALCONSAT:
>
> https://www.amsat.org/wordpress/wp-content/uploads/2018/03/FalconSAT-Stoddard-pdf.pdf
>
> Anyway, it’s a great satellite while mobile that needs no special antennas.
> Just keep up with when it is generally coming over and have the frequencies
> already programmed into a channel in your radio.  Actually, program four
> frequencies to make it easy to shift for doppler.
>
> We will try to remind everyone when passes enter more favorable evening or
> morning commute hours…
>
> And here is a note I got form mailto:himpatrick at wd9ewk.net today:
>
> Bob, WB4APR
>
> *From:* Patrick STODDARD wd9ewk
> *Subject:* Re: [amsat-bb] D72 to Falconsat-3 APRS
>
> FalconSAT-3 uplink sensitivity is good. I regularly work it with 5W from my
> TH-D72 with a handheld beam… I have used a TM-D710G at its various power
> levels, and 5W from the mobile radio works fine.
>
> Downlink power... it is strong. I can hear it a few degrees above the
> horizon.  I have used a TH-D72, TM-D710G, a pair of TH-D74s (The TH-D74
> cannot operate APRS crossband)
>
> I wrote about using these different radios, and combinations of radios, for
> the AMSAT Journal in late 2017:
>
> https://www.amsat.org/wordpress/wp-content/uploads/2018/03/FalconSAT-Stoddard-pdf.pdf
>
> 73!
> Patrick
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