Just in time for the 1-year anniversary of the successful commissioning of the two transponders of Qatar-OSCAR 100, an encore is pending: The capacity of the NB transponder will be expanded from about 250 KHz to almost 500 KHz!

Attentive observers have, of course, long since established that the passband of the NB transponder is actually larger than previously published.

All the more pleasing is the fact that practically 99.9% of the radio amateurs have kept to the previous band plan, which is limited at the bottom by the CW beacon and at the top by the PSK beacon.

The bandwidth of the two NB and WB transponders is determined by so-called surface acoustic wave filters in the S-band receiver, which are marked as SAW in the block diagram of the transponder. By the way, many radio amateurs are mistaken that the QO-100 is merely a commercial TV transponder that has only been switched to our frequencies. But this is far from being the case, the entire AMSAT Payload was specially developed and built according to our specifications. Only a few components could be reused 1.1, including the TWTA. The uplink and downlink antennas were also specially installed for us to cover the entire visible hemisphere and not just one spot beam to Europe. In the commercial sector, people usually work with much greater bandwidths than with our transponders. Particularly with the narrow NB transponder, certain technical limits have been reached, so that the bandwidth here is somewhat larger and the edges are not so steep.

We only became aware of this during the in-orbit test phase. However, since the CW and PSK beacons and LEILA are not generated in the satellite but at the ground station as part of the LEILA box, and since these were designed for the transponder, which was originally only 250 kHz wide, we had initially stuck to the original plans and saw no reason to change them.

Expanding the transponder at an earlier stage was even considered counter-productive. Experience from previous satellites has shown that users are more likely to "get lost" and not find themselves when there is too much space available.

Now, however, in recent months, the operation and occupancy of the transponder, especially in the SSB area, has increased significantly. The use of SDRs with a waterfall diagram also helps users find each other more quickly (and black sheep are also more likely to notice).

On the other hand, however, there were also more incidents with alleged pirates or ignorant people who used the area above the PSK beacon contrary to the band plan. Sometimes unfortunately also with very strong FM signals, which are taboo on the NB transponder anyway.

Unfortunately LEILA could not do anything with her warning signal, because she was limited technically only to the 250 kHz between CW and PSK beacon. On the other hand, it would have been a little bit strange if LEILA would be broadcasting outside the official band schedule

So it was also in the long term a nonsensical and untenable situation that pirates broadcast there undisturbed, while compliant users virtually submit to celibacy. This allowed the pirates to feel rather undisturbed, though not unobserved.

In order to expand the transponder range, no changes are necessary on the satellite. But for this LEILA must be technically upgraded on the ground, because the previous hardware based on the Red Pitaya is not designed for more than 250 KHz and is at the edge of its performance.

Es musste also neben einiger Software-Änderungen auch eine neue Hardware her, sodass LEILA die vollen 500 kHz abdecken kann und bei übertriebener Uplink-Leistung entsprechende Markertöne generiert. Zudem gab es auch Wünsche was die CW-Bake und eine zusätzliche Engineering- oder Experimentier-Bake angeht. Durch die A1A-Modulation mit den Pausen zwischen den einzelnen Punkten und Strichen der CW-Bake, war es manchmal etwas schwierig die Antenne anhand dieses Signals optimal auszurichten. Es gab mehrere Anfragen, ob man stattdessen nicht eine Frequenzumtastung mit konstanten Träger einführt, wie dies auch bei vielen terrestrischen Baken der Fall ist. Mit dem neuen Bandplan wird dies nun ebenfalls umgesetzt.

The upper beacon with the 400 bit/s PSK modulation is essential for many users of QO-100, because it is mainly used by users of the "SDR-Console" by Simon Brown G4ELI (SDR-Radio), or similar programs, to stabilize the frequency of unmodified PLL-LNBs for reception. As the PSK beacon on the ground is very accurate in frequency due to a GPS reference, the drift of the LNB in the SDR receiver can be compensated automatically. Of course we want to keep this, but it will become the new "middle beacon" in the middle of the transponder passband. Users of the SDR-Console only need to adjust the new frequency in the configuration for the Geostationary Satellite Beacon. This is already prepared in the current version SDR-Console. We have placed the PSK beacon in the middle of the transponder so that SDR receivers with a bandwidth below 500kHz can continue to use this function.

New is the future upper beacon, which will be an experimental beacon. In the beginning with CW or PSK, later with sophisticated modulation and efficient protocols, which should allow reception with extremely weak signals. It should be possible to hold the bare LNB in the direction of QO-100 to receive data.

As before, the lower and upper beacon limits the permissible transponder range.

In addition to extended areas for the various operating modes, more space is also being created in particular for "mixed mode" and other special operating cases. In addition to frequencies reserved for emergency radio operations, more experiments are to be made possible here.

But all this only with a maximum bandwidth of 2.7 kHz! Automatic operation requires a special licence from the local licensing authorities and must be coordinated with the operator beforehand; this task is performed by AMSAT-DL on behalf of QARS and Es'hailSat. To take account of user behaviour, we have almost doubled the SSB range in particular.

Mario DL5MLO and Jens DH6BB made some modifications to our ground station DK0SB in Bochum on 14 February 2020 and put the new LEILA hardware into operation. Beacons and LEILA have been broadcast by AMSAT-DL in Bochum since the official commissioning 1 year ago.

The new band plan comes into force with immediate effect.