April 20, 2006  

Unexplained Packet Mail disconnect.

Intermittently the D700 will disconnect from a Mailbox connection without any obvious reasons. In this example, neither the ground station nor the ISS D700 time-out. The link just dropped. There were of course a few stations using the Digi-Repeater with APRS unproto packets. And the PCSat-2 many have been in use on an adjacent channel. However this does not really explain why the link abruptly disconnected.

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]

c rs0iss-11
WF1F>RS0ISS-11 [03/26/2006 12:20:49]: <C>:

RS0ISS-11>WF1F [03/26/2006 12:21:00]: <<I00>>:
Welcome to RS0ISS's message board
System Ver 1.50 110798 Bytes free

WF1F>RS0ISS-11 [03/26/2006 12:21:01]: <C>:
WF1F>RS0ISS-11 [03/26/2006 12:21:10]: <C>:
WF1F>RS0ISS-11 [03/26/2006 12:21:20]: <C>:

RS0ISS-11>WF1F [03/26/2006 12:21:22]: <<UA>>:
*** CONNECTED to RS0ISS-11
RS0ISS-11>WF1F [03/26/2006 12:21:22]: <<I00>>:
CMD(F/K/M/R/W/B/H/?)>

(At this point, I have a successful connection to ISS. 
The index counters have been set to I0,0 starting new
The “I” means Index.
The Index numbers will change from 0-7. The first number is the index reference is for packets coming down from ISS. The second number is the index reference for packet that I am sending to ISS. We both start at 0,0)

WF1F>RS0ISS-11 [03/26/2006 12:21:23]: <<rr1>>: 
(I am sending ISS an acknowledgement that I have received his data and I am ready to receive packet number 1. The last packet I received from ISS was #0, this is the way packet acknowledges that it received #0 is by saying, I am ready for the next packet, in this case packet #1)

WF1F>RS0ISS-11 [03/26/2006 12:21:33]: <<I01>>:S
(Here I am sending the “Send” command to tell ISS I want to upload a packet mail message.)

RS0ISS-11>WF1F [03/26/2006 12:21:37]: <<I11>>: Subject:
(ISS responded with the title “Subject” and adjust the Index numbers accordingly.)


WF1F>RS0ISS-11 [03/26/2006 12:21:38]: <<rr2>>:
(I am sending ISS an acknowledgement that I have received his data the “Subject” title and I am ready to receive packet number 2. The last packet I received from ISS was #1. All of the packet numbers are still in the correct order )

WF1F>RS0ISS-11 [03/26/2006 12:21:43]: <<I12>>:Hi from Miles
(This is the title of my packet mail subject)

RS0ISS-11>WF1F [03/26/2006 12:21:49]: <<UA>>:
(This packet from ISS is an Unnumbered acknowledged, I can mean a few things, here I think it means, it heard my call but lost part of the packet)

WF1F>RS0ISS-11 [03/26/2006 12:21:53]: <<RR2>>:
(My TNC asks the D700 on ISS, Did you get my packet #2 <<I12>> 
The D700 responds with a DM message, which means Disconnect the link)

RS0ISS-11>WF1F [03/26/2006 12:21:59]: <<DM>>:
*** link failed
*** DISCONNECTED

At this point the D700 gets confused the drops the whole connection and issues the DM message.

Things to Note:
Notice the long delays between packets, most delays were on the average of 5 seconds.
Only 10 packets were sent to other ground stations during this packet mail attempt. The packet load was considered low and should not have caused the “Link Failed”.

*******

Here is a listing of some of the other packets that were being process while I was trying to load a message into the Mail box. This type of load is considered a very light load. 

VE3FFR>APRS,RS0ISS-3*,SGATE,WIDE [03/26/2006 12:20:59]: <<UI>>:
=4416.01N/07629.01W- (UIV32N)
WB2YZX>CQ,RS0ISS-3* [03/26/2006 12:20:59]: <<UI>>:

KB1GVR-9>TT4Q5P,RS0ISS-3*,FN54 [03/26/2006 12:21:00]: <<UI>>:
0q 44k/>"4@}

VA2SGL>CQ,RS0ISS-3* [03/26/2006 12:21:22]: <UI>:
=4609.41N/07029.74Wy--73 from Gilles in Quebec {UISS40}

N8DDK>CQ,RS0ISS-3*,FM05PT,DON [03/26/2006 12:21:30]: <<UI>>: U

KI4MDU>APRS,RS0ISS-3* [03/26/2006 12:21:36]: <UI>:
=3356.53N/08444.13W-Hello from Dallas, GA {UISS50}
W1WYC>APRS,RS0ISS-3* [03/26/2006 12:21:37]: <UI>:
=4230.93N/07113.34W-GM All from Fred, Burlington, Ma. FN42jm {UISS41}

KB3CO-2>T0PX6Y,RS0ISS-3*,SGATE,WIDE2-2 [03/26/2006 12:21:48]: <<UI>>:
'g+Pl -/]

WB2YZX>CQ,RS0ISS-3* [03/26/2006 12:21:48]: <<UI>>: hi! QSL VA2SGL..

KB1GVR-9>TT4Q8W,RS0ISS-3*,FN54 [03/26/2006 12:21:48]: <<UI>>:
0JoRlk/>"4L}TH-D7A(G)

KB1GVR-9>TT4Q9P,RS0ISS-3*,FN54 [03/26/2006 12:21:59]: <<UI>>:
05 4jk/>"4W}

RS0ISS-11>WF1F [03/26/2006 12:21:59]: <<DM>>:
*** link failed
*** DISCONNECTED


Special Version of the D700:

The D700 Voice/Packet system has been programmed in a very complicated manner. The software in this model is not the same software found in production versions of the D700. It is a customer burn of software that includes some specific features requested by the ARISS project team. 

This radio is also Dual-band Transceiver, which means there are two radios built into one box. Normally most people on Earth use Radio-1 for VHF and Radio-2 for UHF operations. A simple toggle button allows you to switch been radios. In the special ARISS version, configuration Both Radios are used at the same time for most operations. For example in Packet mode both radios are set for VHF, Radio-1 is set for the Receiving radio and Radio-2 is configured for the Transmit radio. The Packet/TNC listens for data on Radio-1 and transmit its response back on Radio-2. A similar configuration is also used for normal voice communications.


Conclusion:
These unusual configurations may be part of the reason the Packet/TNC part of the project has many usual quirks that do not appear in the Terrestrial version of the same radio.

In this specific problem were not sure why the D700 dropped the link. It is normal that under very busy conditions for your station to RETRY out and drop the connection. If that was the case, you would have seen RETRY packets coming down from the D700 or going up from my TNC. 

Here is one theory: The D700 on ISS has its TNC programmed for FULL-DUPLEX. The radio is configured for Half-Duplex. 
Normally you will configure the TNC to match the radios mode of operation; in this case both should be Half-Duplex. The D700 TNC may be sending commands while it is still in the Receive mode. This is because it thinks it has a dedicated Transmitter and it can transmit any time, without waiting for the receiver to stop. 

Just a theory.