[TMRA] Additional JT-65 information from Jan club meeting

[Robert Hall]

*Below is a little additional information for those that attended the JT65
presentation this evening.  This should answer a few of the remaining
questions and provide a couple clarifications.  Feel free to email me with
any questions at rhall987 at robhall.org <rhall987 at robhall.org>.  Enjoy.  -
Rob KV8P*


*1.  JT65-HF vs WSJT-X:  *We only looked at the JT65-HF software this
evening, however, the WSJT-X software is more powerful (more functions) and
includes all of the base functions are there and are identical to what we
discussed.  Things might look a little different, and you can select other
modes (like JT-9), but the functions are the same.

*2.  Signal reports* are specified as signal-to-noise ratio (S/N) in dB,
using a standard reference noise bandwidth of 2500 Hz. Thus, in example
message (G0XYZ K1ABC –19), K1ABC is telling G0XYZ that his signal is 19 dB
below the noise power in bandwidth 2500 Hz. In message (K1ABC G0XYZ R–22),
G0XYZ acknowledges receipt of that report and responds with a –22 dB signal
report. JT65 reports are constrained to lie in the range –30 to –1 dB,
while JT9 supports the extended range –50 to +49 dB.  This is only item I
forgot to mention, as a difference, for those that would then like to try
JT-9.

ALSO:  Signals become visible on the waterfall around S/N = –26 dB and
audible (to someone with very good hearing) around –15 dB. Thresholds for
signal decodability are approximately –24 dB for JT65, –26 dB for JT9.



*3. Some links for those that are interested:*

http://dimension-4.en.softonic.com/     D4 Time Sync. software

http://jt65-hf.com/downloads/ <http://jt65-hf.com/downloads/>   JT65-HF

http://physics.princeton.edu/pulsar/k1jt/wsjtx.html   WSJT-x Software

http://nw7us.us/jt65a.html    More great information about JT-65!



*4. What is JT65-A?*  There have become a lot of sub-modes of JT65.  JT65-A
is just JT65 used for HF and VHF using the software.



*5. Some 40m freq. clarifications:*

 7036.0 / USB   (International)

  7039.0 / USB   (Typically Europe)

  7076.0 / USB   (USA)



*6.  NO ALC when transmitting please:*  One large item I forgot to mention
tonight, about transmitting in particular, is that you want to make sure
you tune the sound card so that NO ALC is occurring when you are
transmitting.  Just back down the TX audio going to your rig just until NO
ALC is occurring (your power will be the same, but your signal will be much
cleaner!)  This is how you know that you are not overdriving your
transmitter in this mode.  Yes, if you back the TX audio too far back, past
that, your power will drop off as well.  Just find the “sweet spot” where
your ALC is gone, but your Power didn’t drop yet.  I’ll add this to future
presentations.  :)


*73,*

*Rob KV8P*