locked IRTS HAREC Study Guide: Please Help Review the #FT8 Section #FT8


Rafal Lukawiecki EI6LA
 

The Irish Radio Transmitters Society, IRTS, have just released a prepublication draft of our upcoming HAREC Study Guide. It is aimed at those who want to pass the Irish HAREC licensing exam. I led the team that wrote the guide. I would like to ask anyone interested to help in reviewing it, especially the short section 11.10, pages 153–154, which briefly covers FT8 and mentions WSJT-X.

Feedback on the remainder would be also welcome. We plan to incorporate it by late spring next year, in time for the guide's publication.

Please download the guide PDF (25 MB) from https://irts.ie/guide

The announcement and a few words about the history of this book is at: https://groups.io/g/IRTS/message/1445

Feedback can be emailed directly to me, raf (at) rafal (dot) net.

Thank you!
Rafal EI6LA


Barry Bogart
 

The ft8 section is at p 167 (according to my PDF viewer), although I'd recommend that people read more of the guide, which I find very good. I will probably read the whole thing as there is still too much snow to go out.

If I wanted to nitpick, I’d say the attention paid to the ITU modulation type designators is not necessary. But I admit I always wondered how they were derived. Maybe they are covered in the exam, though. I haven't taken one in a while!

Barry, VE7VIE


Reino Talarmo
 

Feedback on the remainder would be also welcome. We plan to incorporate it by late spring next year, in time for the guide's publication.
Feedback can be emailed directly to me, raf (at) rafal (dot) net.
Hi Rafal,

I like to provide some feedback on this list about FT8 so that all interested parties have a hint what is fed back. First of all the guide is an excellent and very useful source of radio amateur technics.

Page 153 clause 11.10
One essential issue in the FT8 coding is the source coding. Perhaps the text should be expanded a bit stating that the operator sees on the Band Activity message display much more characters than is actually sent. In the short message fits in only (exactly) 13 characters of a free text, but source coding support messages that are up to 22 characters long. Of course the source coding sets strict limitations e.g. to the call sign structure and other message elements that can be sent with the call sign. E.g. contest messages cannot use special call signs. That issue seems to be hard to understand to some operators.

In addition FT8 uses error detection to facilitate a removal of most erroneous messages (and for selection of correct messages).

(One essential issue about decoding FT8 or almost any digital modulation are time and frequency synchronizations and how much of the transmit power is used for it, but normal user don't see it in FT8 except the raw time sync order of one second.)

Footnote 188 could continue "... Franke and Taylor 8 tone FSK."

Page 278 footnote 320
Perhaps FT8 as an example about minor error correction is not fare. Before error correction received signal in FT8 can be almost unreadable due to errors even taking into account the source coding.

I don't really know whether I am on a proper track about how deep a guide should go in details for the intended purpose.

73, Rein OH3mA