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The validity of amateur QSOs made in the JT65 digital mode has
been questioned because the amount of transferred information
can be very low.
Surely one can have different opinions about how to value a low amount of transferred information, but there should be no differences in opinion about how a mode works and what kind of information actually is transferred. SM2CEW, Peter, started a debate here in Sweden by having an article published in QTC no 11 2007. Read it here QTC-11.07 (Swedish) or here QTC-11.07 (English) These articles are technically incorrect in several ways and for that reason I found myself forced to write an article trying to make clear to QTC readers how the DS decoder of JT65 actually works. My article was published in QTC 8 2008. Read it here: QTC-08.08 (Swedish pdf) or here QTC-08.08 (English) Peter has written a reply to me which was published after my article in the same issue QTC-08.08 (Swedish pdf) an English version is available here QTC-08.08, Peters reply (English, my translation) It is quite obvious that I have failed in my attempt to make Peter understand where he makes errors in his thinking. JT65 is not a bad mode and contacts are not made via the Internet. The advantage of using the DS decoder is very small because the option to average over a couple of transmission periods is a possibillity to receive very weak signals without the DS decoder. What Peter is doing that makes me very upset is to discredit the JT65 protocol technically for political reasons. Politics, how to compromise between legitimate but opposite interests between different groups, is one thing. There is no question that a DXCC in CW is much more difficult than one in which JT65 has been used. What conclusions to draw from that regarding rules for contests, diploma and top lists is a political issue. When regarding achievements in contests or diplomas like results in sports, surely something more difficult is a greater achievement. There are other ways in which EME contacts can be made more difficult, my own way is to refuse to use skeds. This link Mixed contests are needed in EME is an attempt to explain why my opinion in politics differs from Peters and why I find his political position harmful to our hobby and counter-productive for the long-time survival of CW. Technically, it is uncomplicated. JT65 is a fine mode. What is transmitted with this protocol is perfectly legitimate for random contacts between all regular amateur call signs. The standard protocol does not automatically support DXpedition callsigns with nonstandard add-on prefixes, but that is a technical problem that is easily solved. The idea that JT65 as a mode must be banned because some operators use the short-cut given by the DS decoder to avoid having to wait for a decode on averages does not make sense. Does Peter really want to declare Morse coded CW non-valid the day I add a DS decoder to my computerized CW decoder? Maybe I just use it myself secretly. Then CW would be fine - but in case I make CWDS publicly available, would I make Morse coded CW as a mode for ever non-valid ? Peter does not like it, but the methods used by an operator to decode a message is strictly the operators own bussiness. Klaus, DJ5HG gave a lecture at the EME 2008 meeting The Cat and the Squirrel in Florence which very clearly explains the fundamentals of communication. Have a look also at the slides from his talk He says:"The transmitting station does not intentionally switch. between different signals to communicate information which is unknown to the receiver. Therefore, the distance value (or it's inverse the correlation value) does not contain any information via the radio path." This statement is applicable to sked contacts where the receiving station knows what message will be transmitted. It is exactly the same in Morse coded CW and in JT65. In both cases not a single bit of information is transferred via the radio path in the first sequence of a sked QSO. One only evaluates a single probability that the received waveform is noise plus the known waveform rather than noise only. Whether the computation is done in the operators brain or whether it is done in a computer does not change the physics of the process. Klaus makes his own interpretation of QSO rules like this: There are two types of requirements:
There was a discussion about related issues at the Florence meeting that ended up in the conclusion that trying to make rule changes would not be a good idea. We should trust in ham spirit and make sure that our own operating procedures set good examples for others. To SM 5 BSZ Main Page |