Hi Jose
My radio was monitoring 40m last night when I was sleeping . My antenna
is a homemade vertical dipole for 20m
and I was surprised to see your signal on my screen this morning.
Would you make it another try to night and I promise you I will stay
awake to try to connect you ?
73 de LA5VNA Steinar
Jose A. Amador wrote:
I finally read the WSJT manual, quite quickly indeed, and from it I
could gather the following:
Encoded user information is transmitted during the 63 intervals not
used for the sync tone. Each channel symbol generates a tone at
frequency 1275.8 + 2.6917 Nm Hz, where N is the value of the six-bit
symbol, 0 N 63, and m is 1, 2, or 4 for JT65 sub-modes A, B, or C.
The signal report OOO is conveyed by reversing sync and data positions
in the transmitted sequence. Shorthand messages dispense with the sync
vector and use intervals of 1.486 s (16,384 samples) for the alternating
tones. The lower frequency is always 1270.5 Hz, the same as that of the
sync tone, and the frequency separation is 26.92 nm Hz with n = 2, 3, 4
for the messages RO, RRR, and 73.
So, assuming N is the 63rd symbol in JT65A (m=1), it yields:
1275.8 + (2.6917 * 63) = 1275.8 + 169.5771 = 1445,3771 Hz
The shift is less than 170 Hz !!
And for 73:
1275.8 + (26.92 * 4) = 1275.8 + 107,68 = 1383,48 Hz
The shift is 107,68 Hz!
So, JT65A never occupies more than 170 Hz on the air, which is quite
tolerable indeed.
Figuring out all this, I wanted to corect my previous post. Yes, it is
wider than PSK31, but not quite as wide as RTTY.
73,
Jose, CO2JA
PS: I have been monitoring quite a few QSO's on 7076 this evening!
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