A statement of the VHF-DX-Group DL-West (update)
Since middle of July a new abbrevation has kept showing up on the DX-Cluster:
WSJT is the title of a PC software package and stands for "Weak Signal
communication by K1JT". This new mode has been developed particularly for
Meteorscatter, and is based on the modulation concept of FSK441. The message
is coded by 4 tones, and WSJT may be considered as a kind of radioteletype (RTTY).
The transfer rate is about 8800 lpm. The oustanding feature of the program is
the ability to decode signals at very weak levels.
FSK441 in the form of WSJT represents an interesting mode for running meteorscatter experiments. It has already brought a large number of the old boys back on the band, and moreover motivated also several newcomers to try MS on 2 m. This certainly deserves our credits. Unfortunately, the rapid development has brought about also some negative aspects, which will be discussed futher down.
1. Choice of frequency: The first attempts in Europe where run on 144,150 MHz. Because of reciprocal interference with traditional MS-operations there, the WSJT community has quickly moved on to the upper SSB-range. Since FSK441 is a weak signal mode, one may argue for staying in this part of the 2 m band. A suitable segment in accordance with the present practice might be 144,370-144,395 MHz. But it shall not be concealed that the reduction of the SSB range could lead to interference at least during major contests (note that WSJT offers most advantages outside major showers, when there could be contests). Interference with other contacts is likely to pass unnoticed by the WSJT operator, because he will not necessarily monitor the frequency by ear. On the other hand, the communication in WSJT is purely digital and from machine to machine. This would advocate for an allocation above 144,800 MHz, in the range designated for digital modes. There might also be a larger segment available. However, we understand that most WSJT users do not favour such allocation. Because of its weak signal advantage, WSJT will probably become common also on 432 MHz, where frequency allocation due to the lower activity should be less critical. It might be a good idea to assign calling frequencies on both bands, as for other modes. In order not to establish unchangeable habbits, the final and official allocation should be agreed upon rather quickly.
2. Operating practice: There seems to exist a widespread confusion about when a WSJT contact is considered as complete. The application of the standards for traditional MS, as published in the IARU Region 1 VHF Managers Handbook, seems perfectly reasonable. Since a growing number of WSJT operators are not familiar with traditional MS, an adequate information campaign should be launched. Moreover, WSJT has its origin in the US, where somewhat different MS standards are practiced. This might explain why many contacts are reported in full detail over the DX-Clusters, including both reports and final rogers. If WSJT would be practiced according to well defined and proper standards, it could develop to a viable complement to the traditional HS-MSCW mode.
3. Period length: WSJT is currently operated with 30 seconds periods. This complicates the co-allocation with traditional MS modes, where either 2,5 minutes (CW) or 1 minute periods (SSB) are used, because a third sequencing pattern is introduced.
4. Automation: We would not like to see automated operation implemented into WSJT, or for that sake any other mode that will be used within the weak signal communication range from 144,000-144,400 MHz. We fear that automated operation will increase the risk of interference and erratical response in case of unusual situations. We propose to prohibit automated operation in the frequency range 144,000-144,400 MHz, regardless of mode.
5. Misinterpretations: WSJT decodes the received signals automatically. It is likely, that QRM situations could lead to decoding errors. The WSJT software permits the use of so-called single-tone messages, that complicate the identification of the other station. What happens when using single-tone messages in case of QRM or Doppler-shift of signals (which is not unusual in MS)? The users of WSJT are encouraged to cooperate with the author of the software in the further development, so that misinterpretations will be avoided. For the time being, the use of single-tone messages is discouraged.
6. DX-Cluster: As mentioned above, quite frequently complete WSJT contacts are mirrored over the DX-Cluster. This has been observed also with traditional MS contacts, but by far not to the same extend as with WSJT. Are users doubtful about the correctness of the details received on the band? Self-spotting is quite common, probably due to the lack of a calling frequency. This type of QSO mirroring leads to clogging of the cluster (a nuisance during times of high activity), as well as it includes the possibility of cheating. We fear the credibility of MS-contacts in general is being undermined. We recommend to have the IARU prohibit the transfer of critical QSO details (at least the report) through DX-Cluster and WW-Convers mode. This should apply also to other operating modes, not only to WSJT. Similar rules are already applied in another context: The ARRL disqualifies contest-participants that use DX-Cluster for unfair competion, e.g. self-spotting.
With this document, the VHF-DX-Group DL-West would like to comment on the present confusion and interference related to the use of WSJT, as observed particularly during the Perseid shower 2001 in the densely populated parts of western Germany. Our desire is to voice the demand for a proper operating framework, as it should be developed by the IARU Region 1 VHF comittee.
Copies of this statement will be submitted to the following parties:
" Members of the VHF-DX-Group DL-West (published on http://www.rue.net/vhfdx/
)
" VHF-Reflector (vhf@ww, in PR)
" WSJT-Reflector ([email protected], by internet)
" MS-Reflector ([email protected] , by internet)
" PA0EZ (Chairman IARU Region 1 VHF Committee)
" DL2OM (VHF columnist for the CQ-DL magazine)
" DF7VX (VHF-Referee of the DARC)
" DL1UU (VHF columnist for the Funkamateur magazine)
" DL8HCZ (DUBUS/FT editor)