March 27, 2006  

Unexplained Packet Mail Retry:

This is an example of a typical Retry Timeout. Most of the time you will see this type of time out happen, when the Station that is logged into the Mail box, goes out of range. It can also happen if there is a sudden increase in the number of stations trying to use the D700 packet system with either Unproto packets, APRS packets or Mail box login attempts. 

De-Sense problem?
In this case the ground station was in Range and running lots of power. And there were very few APRS packet users. This problem more closely resembles a similar problem we had with the Mir packet system called De-sense. When the Mir crew turned on their transmitter on 143 MHz, it would De-sense the Amateur Radio packet system on 145.985 MHz. The Amateur Radio station logged onto the packet system before the 143 MHz was activated, would not be able to continue his packet connection, no matter how much power he had available to him. The Packet TNC would them time out and start sending down a string of RETRY packets until the system timed out completely and issued a disconnect message.

Unfortunately even though this looks on the surface like a De-sense problem, it may not be. De-Sense would also block ALL signals from other users, including APRS packet users. There were 10 packets from APRS users randomly dispersed in-between the Mail box RETRY time out messages.

It almost looks like the Mail Box portion went selectively Deaf and ignored Mail box packets, while still processing APRS packets.

Setup:
Earth, KPC-3 TNC, Yaesu FT-736R (Doppler correction was used), AZ-EL Antenna system with 12+ dBd gain, ERP more than enough. The pass was a 30-degree pass and the number of active packet users was low. During this test, ISS sent only 10 packets to other ground stations. This test lasted 1 minute and 10 seconds [12:20:49 - 12:21:59]

Problem:
Connected to ISS and tried to send a 3 line message. I was able to get past the “Subject” section of the message, then the D700 failed to acknowledge the rest of the message. The Retry timer started and timed out after 1 minute and 30 seconds [12:23:14 -12:25:44]. ISS was still in range and signals were still very strong. ISS was sending out a few Unproto packets successfully. It was just not responding to Packet Mail.

Short Packet Lesson:
Packet data is tracked by Index numbers <I23>. The sending station always places their packet index number First, and the receiving stations counter second. When the receiving station sends a packet back, these numbers will look reversed.
Acknowledge packets:
When a receive station gets data, it will respond with ACK packet that will be one number greater than the last packet received.
<<rr5>> which means, I have received packet #4, I am waiting for your next packet number #5. It also means, that if you send multiple packets at once, all packets up to and including #4 were decoded correctly. The small letters “rr” means that this response was generated automatically by the receiving end of the conversation.

The capital <<RR6>> is more like a demand request, “Hey you did you get my packets!”
In this example, did you get packet #5 and are you ready too receive packet #6.

c rs0iss-11
WF1F>RS0ISS-11 [03/26/2006 12:22:08]: <C>:


RS0ISS-11>WF1F [03/26/2006 12:22:10]: <<UA>>:
*** CONNECTED to RS0ISS-11
RS0ISS-11>WF1F [03/26/2006 12:22:12]: <<I00>>:
Welcome to RS0ISS's message board
System Ver 1.50 110798 Bytes free

WF1F>RS0ISS-11 [03/26/2006 12:22:13]: <<rr1>>:
RS0ISS-11>WF1F [03/26/2006 12:22:16]: <<RR0>>:
WF1F>RS0ISS-11 [03/26/2006 12:22:17]: <<rr1>>:

RS0ISS-11>WF1F [03/26/2006 12:22:24]: <<I10>>:
CMD(F/K/M/R/W/B/H/?)>

WF1F>RS0ISS-11 [03/26/2006 12:22:26]: <<I02>>: S
RS0ISS-11>WF1F [03/26/2006 12:22:27]: <<I21>>: Subject:

WF1F>RS0ISS-11 [03/26/2006 12:22:28]: <<rr3>>:
WF1F>RS0ISS-11 [03/26/2006 12:22:44]: <<I13>>: Test from miles

RS0ISS-11>WF1F [03/26/2006 12:22:46]: <<I32>>: Message:

WF1F>RS0ISS-11 [03/26/2006 12:22:49]: <<rr4>>:
(I have received ISS packet #3, waiting for #4. This packet acknowledges the Message banner. )

RS0ISS-11>WF1F [03/26/2006 12:22:50]: <<RR2>>:
(ISS, has received my packet #1, waiting for packet #2)

WF1F>RS0ISS-11 [03/26/2006 12:22:51]: <<rr4>>:
(I have received ISS packet #3, waiting for #4. This packet acknowledges the Message banner)

WF1F>RS0ISS-11 [03/26/2006 12:23:03]: <<I24>>: march 26, packet test.
WF1F>RS0ISS-11 [03/26/2006 12:23:03]: <<I34>>: have fun on ISS, Miles wf1f
WF1F>RS0ISS-11 [03/26/2006 12:23:03]: <<I44>>: /ex

(In this example, I sent 3 lines of data for the body of a packet mail message.
The D700 never acknowledged any of the polls. My TNC asks the D700 15 times, if it received packet #4. The D700 never responds.)

RS0ISS-3>P0PPP0,SGATE,WIDE [03/26/2006 12:23:12]: <<UI>>:
'vX l '/]APRS/BBS & PACKET ON.