Maintenance M7/M7L/M7LT Modular Satellite Modem
4-14 M7/M7L/M7LT - Rev. 0.05
4.7. Frequently Asked Questions - FAQ
OR How Do I? Why Doesn’t It? and Where Is?
This section is intended to form a smart index pointing to proper sections of the manual with
information on performing common actions or answering common questions. The presentation here is
divided into 5 common areas – Link Setup, Front Panel, Remote Control, Data Interface and Manual.
4.7.1. Link Set Up and Installation.
4.7.1.1. Compatibility with other Modems.
4.7.1.1.1. How do I make the M7 talk to a “x” brand modem on the other end of a link?
The M7 has several new programmable features which should make this easier than ever. First,
where possible if both modems adhere to Intelsat IESS standards then those defined parameters
should be set the same. Still all modem manufacturers have their own conventions for setting
parameters with no specified standard, so for example some modems may have a different
modulation sense for data bits than others. This would make no difference between two modems of
the same type, but would invert data between modems of different types on each end of a link. Most
items of this type are programmable in the M7 modem.
The M7 also has a significant number of FEC compatibility modes for aid in achieving compatibility
with some competitive modems, especially in Turbo FEC modes. These modes are denoted by the
FEC Option type “CT” on the front panel selection.
4.7.1.1.2. Is Datum Systems' Turbo Product Codes compatible with that made by other
modem manufacturers?
The M7 also has a significant number of FEC compatibility modes for aid in achieving compatibility
with some competitive modems, especially in Turbo FEC modes. These modes are denoted by the
FEC Option “CT” on the front panel selection. These modes are typified by the modes used in the
CDM5xx and CDM6xx series of competitive modems.
There are several modes that are probably not compatible for several reasons. First is that
there is no standard for implementation of TPC. Second, Datum Systems spent a lot of time
and development in implementing a full set of TPC parameters (i.e. Rates 1/2, 3/4 and 7/8),
and insuring the absolute best performance with no compromises. We have seen no other
TPC implementation that even comes close to ours. Third, because we have many
customers that use our modems in systems requiring low latency we implemented an
alternate "Short Block" mode that reduces the typical TPC delay by approximately 1/3. The
techniques used in this TPC achieve the best performance of any modem currently produced.
Our latest TPC “Advanced” modes are also proprietary to Datum Systems, simply because
we know of no one else using the specific parameters.
4.7.1.1.3. Is the M7 Remote Control Protocol Compatible with the PSM-4900?
The M7 has significant new capabilities and features that cannot fit into the structure of the PSM-4900
protocol. However, the M7 will respond to properly formatted PSM-4900 binary control packets within
the capabilities of the PSM-4900. This allows mixed systems of 4900 and 500 series modems without
initially changing control software. The compatibility does not currently extend to operation over the
link on the MCC channel.
4.7.1.2. Operating and Performance Questions.
4.7.1.2.1. There are so many options and parameter settings! Where do I start?
The M7 is highly programmable. This can make the set-up daunting at first. If you are unfamiliar with
the common terms and modes used in satellite communications you should first refer to Chapter 2 of
this manual “Installation and Setup”. As a starting point the modem can also be taken to a default
basic set of operating parameters by using the front panel <Unit: Configuration - Recall> parameter
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