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Maintenance
PSM-500/500L/500LT SCPC Satellite Modem
My PSM-500 and PSM-2100 do not agree on the Eb/No parameter with Reed-Solomon
Codec installed?
The PSM-2100 was designed before Intelsat IESS 309 added the section defining how the Eb/No
was measured with Reed-Solomon concatenated coding, and uses a different method. The
method is encapsulated in ASIC and not changeable. Unfortunately the IESS lists two possible
methods of computing the Eb/No with Reed-Solomon. The PSM-500, being of more recent
design, adheres to both IESS definitions by allowing the reference point to be varied. The two
therefore may read differently, but actually achieve the same performance. Refer to Appendix RS
for more information on setting the calculation parameter.
Does the PSM-500 have AUPC and AUFC and are they compatible with the PSM-2100?
The PSM-500 does not have AUFC, but retains the AUPC from the PSM-2100 type modems.
Like the PSM-2100 the built in AUPC (Automatic Uplink Power Control) can be enabled only if the
multiplexer option is installed or if an external communications channel is provided.
The PSM-500 AUPC is compatible with that in the 2100 when the PSM-500 modem IBS
Multiplexer is placed in the "Enhanced" mode. It is not compatible in the "Custom" mode.
How do I set up the IBS Multiplexer and AUPC Option in the PSM-500 to be compatible
with the PSM-2100 Modem?
The PSM-500 Modem is capable of varying the parameters for the IBS Multiplexer beyond the
capabilities of the PSM-2100. To maintain compatibility with the PSM-2100 specific similarly
named options are available in the PSM-500. These modes are the "Standard" and "Enhanced"
multiplexer operating modes. The 500's "Custom" mode is not compatible with the PSM-2100.
For the AUPC to function and to be compatible with a PSM-2100 it must be set in the "Enhanced"
mode.
How do I set up the Reed-Solomon Option in the PSM-500 to be compatible with the PSM-
2100 Modem?
The PSM-500 Modem is capable of varying the parameters for the Reed-Solomon Codec beyond
the capabilities of the PSM-2100. To maintain compatibility with the PSM-2100 specific similarly
named options are available in the PSM-500. When enabled the RS FEC Mode should be set to
"IESS-308". This will automatically set the "n", "k" and "Depth" options to 126, 112 and 4
respectively. The 500's "IESS-309" and "Custom" modes are not compatible with the PSM-2100.
A.2 Operating and Performance Questions.
There are so many options and parameter settings! Where do I start?
The PSM-500 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 and select option "0" or "Factory". From that point you make
necessary changes to set the desired configuration. Once all parameters are set as required the
configuration can be saved using the <Unit: Configuration - Store> control. From there you can
always go back to this configuration by recalling it.
Why doesn't my PSM-500 talk to another PSM-500 over the satellite? I have set all the
parameters the same.
Any satellite modem has a significant number of parameters, which are settable in order to
achieve the maximum performance at the least cost. Because there are so many parameters it is
possible to have one unit with a slightly different parameter set than that at the other end of the
Page 4-16
PSM-500/500L/500LT - Rev. 0.91
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