TNC Configuration to support the D700 on ISS:

The D700 Packet Mail system on the ISS is having a few problems. One of the problems is a long packet delay issue. During Mail Box connections the packet response time is much longer than other TNC’s (typically 5 seconds plus). The Delay problem will cause most terrestrial users to Time-out or go out of range before they are able to complete a Mail box session. There is also a problem with the D700 inability to send an Acknowledge packet when you are uploading Message text. Because of these and other issues, it is much harder to use the D700 on ISS for a Mail box system. If you used the ISS PacComm Mail Box or the old Mir KPC-9612 you will notice a big different in performance between those units and the current ISS D700 system. The packet Delay problem will also affect Unproto operations, but they are not as sever as they are with Packet Mail. If you wish to use the D700, you will need to make additional changes to your TNC in order to partially compensate for the delays from the D700 on ISS.

Most of the parameter changes required for the D700 will be compatible with terrestrial BBS operations. Using these suggested parameters will improve your connection link stability with the D700 and at the same time help reduce Interference (QRM). The only down side, is that if you used these settings for terrestrial BBS activity, your actual data though put on Earth may be slightly lower. The only value you will want to disable during terrestrial activity is the MCON value, which should be OFF for terrestrial and ON for ISS

Note: The Unproto / APRS features of the D700 are much easier for beginners to Access than the Mail box. If you wish to experiment with the ISS packet system, I would suggest you start with the Unproto and APRS options. The MAREX web page has several good information postings on how to use these features.
http://www.marexmg.org/fileshtml/howtouseiss.html

This is a portion of the TNC parameters in my KPC-3; your actual parameters may vary:

AX25L2V2 ON
AUTOCR OFF 
FRACK 10 (seconds)
LFADD OFF 
MAXFRAME 2 (2 packets)
MCON ON 
MCOM ON 
MONITOR ON 
PACLEN 72 (72 character long or less)
RELINK ON
RETRY 8-10 
TIME STAMP ON 


AX25L2V2: This value configures the version of your TNC. Version 2 is the latest. One of the big advantages between V1 and V2, if using V1 and you send 3 packets at once, if the far end rejects any packet, you will have to send all 3 again. With Version 2, you only need to send the packets that were damaged and not all of the packets.

FRACK: This is the most important change to support the D700 on ISS. This is the amount of time to wait for the far end TNC to respond with a packet acknowledgement. The default is usually 4 seconds. With the ISS D700 there are very long delays in sending return packet acknowledgements. It is normal to wait 5 seconds or more for a packet acknowledgement. There are also times when you are sending data such as Mail box text, the D700 does not automatically Acknowledge the packets. Your TNC must soft-time-out and specifically ask for a poll packet acknowledgments. Setting the FRACK timer to 10 seconds will help reduce the number of RETRY time outs.

LFADD: This value seems to interfere with normal ISS BBS operations. Make sure LFADD is turned OFF. 

MAXFRAME: This is the maximum number of packets your TNC will send at one time. Keep this value small, on Earth 4 frames is normal for the D700 try 2 frames.

MCON: This value is normally turned "OFF" for terrestrial BBS connections, and "ON" for connections to the ISS PMS. This value will allow you to see packets going to other stations, while you are connected or attempting to Connect. All courteous operators using ISS will keep this value ON. 

MCOM: ON

MONITOR: ON 

PACLEN: Use a shot character length of 72 or less. Lots of short packet lengths are less likely to be clobbered than a few very long packets. 

RELINK: The Relink option may help you to keep the link going during a long email session.

RETRY: A value of 8-10 should be sufficient. You do not want to set this value too high because you may cause QRM during your initial connect. Also, if "RETRY" is too short, you may time-out during the one of the 4 deep RF signal fades. During a 10-minute pass, there will be 4 RF polarity shifts in the signal coming from ISS. This shift is caused by the apparent change in orientation of the ISS antennas in relation to your antenna. The FRACK timer needs to be set to 10 seconds between Retry.

TIME STAMP: With Time Stamp turned on, you will be able to log data to your disk while you are away and track the time and duration's of the passes.

How much power do I need?

Always use the least amount of power needed for the required operations. With that said, you will need less ERP if you are just going to use the Unproto / APRS options. If you want to use the D700 Mail box you will need More. And it may take you 2-3 minutes to down load or upload 1 message. Make sure you time your passes with plenty of time to complete your planed task.

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.
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.