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

[Robert Bruninga]

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