Receiving MIS + PLS Transponders on Eutelsat 5.0°W with Max SX8 (Pro)

Receiving MIS + PLS Transponders on Eutelsat 5.0°W with Max SX8 (Pro)

Introduction

Some transponders on Eutelsat 5.0°W using Multistream (MIS) and Physical Layer Scrambling (PLS) may fail to lock correctly on certain hardware. A common example is 12606 V, where stream 4 does not lock at all, and stream 5 locks with a very low bitrate (~6 Mbps instead of ~35 Mbps).

This behavior is not related to driver issues but instead to hardware limitations in the STID135 demodulator used by the Max SX8 (Pro) cards.

Problem Description

• Transponder: 12606 V (Eutelsat 5 West B)
• Multistream 4: No lock
• Multistream 5: Locks but unstable bitrate (~6 Mbps, CC errors)
• Other transponders (e.g., 12564 V MIS 5): Work correctly

Tests with a Bridgetech Nomad probe confirmed that the antenna and RF path are fine — all transponders are received normally, even with a 6 dB attenuator.

Nomad output shows ISSY (Input Stream Synchronization) enabled, which appears to trigger the limitation in the STID135-based hardware.

Root Cause

The issue stems from the STID135 hardware demodulator used in the SX8 (Pro). When ISSY is enabled, the demodulator cannot properly deliver MPEG-TS in standard mode for these streams.

The only reliable solution is to switch to BBFrame (Baseband Frame) mode, which outputs the raw BBFrame stream directly from the demodulator.

Solution

To lock on MIS + PLS transponders with the Max SX8 (Pro), use BBFrame mode with the ddzap utility. This mode embeds the Baseband Frames into an MPEG-TS container for further processing.

Example Command

ddzap -d S2 -f 12606000 -s 35300000 -p v -g 131070 -i 0x80000000

The -i 0x80000000 flag enables BBFrame mode. You should now obtain a lock and receive the full BBF stream. To extract the actual MPEG-TS content, the BBFrame stream must be unpacked.

Extracting MPEG-TS from BBFrame

You can use the provided bbf.c utility (download) to convert BBFrame data back to a usable transport stream.

Build the Utility

gcc -o bbf bbf.c

Usage

./bbf <stream_id> < bbfts > outts

Example for the RAI transponder:

./bbf 4 < 5w.ts | vlc -

This command extracts the transport stream for stream ID 4 and pipes it to VLC for playback.

Using BBFrame Mode with TSDuck

TSDuck can process BBFrame output from ddzap. Two example commands are shown below — both tested on Debian 12.

Option 1: Using tsp -fork

tsp -I fork "ddzap -d S2 -p v -f 12606000 -s 35300000 -g 131070 -i 0x80000000 -o | bbf 4" -O file test.ts

Option 2: Pipelined

ddzap -d S2 -p v -f 12606000 -s 35300000 -g 131070 -i 0x80000000 -o | bbf 4 | tsp -O file test.ts

Both will save the extracted MPEG-TS stream to test.ts. The first method is preferred when handling multiple live transponders simultaneously.

Conclusion

If MIS + PLS transponders fail to lock or show low bitrate on Eutelsat 5.0°W, the cause is likely the STID135 hardware limitation with ISSY-enabled streams.

Switching the Max SX8 (Pro) card to BBFrame mode resolves the issue. Use the ddzap command with the -i 0x80000000 flag and bbf.c to extract the MPEG-TS stream.

This approach provides a stable lock and full bitrate reception for affected MIS transponders.

Additional Notes on Parameters for ddzap

 Important clarification

• The -g parameter sets the gold code (used in multi-stream setups).
• For most MIS transponders, you’ll use -r for the PLS root code.
• In some rare cases, both -r and -g may be required, depending on the satellite.

Stream ID is also important — it’s not always 0. When using BBFrame mode (-i 0x80000000), the lower bits of -i define the MIS ID.

For example, on Eutelsat 5.0°W, 12606 V (PLS 131070), with stream IDs 4 and 5:

 # Stream ID 4

ddzap -d S2 -p v -f 12606000 -s 35300000 -r 131070 -i 0x80000004

# Stream ID 5

ddzap -d S2 -p v -f 12606000 -s 35300000 -r 131070 -i 0x80000005