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e7854d6c5b
Using the reference spectrum discards a short part of the front of the period's received samples which may have contained a decode candidate. As far as the MSK modes are concerned the reference spectrum correction is probably not applicable anyway. Comment from Steve K9AN after offline discussions about this: "In any case, I don’t think that there is any reason to apply the reference spectrum correction to the MSK modes. I do think that we are paying a performance penalty in the MSK modes for non-ideal filter responses at the TX and RX ends of the link — but we would need to implement an equalizer that looks at the received sync words as a “training sequence” in order to come up with anything that could improve the results. This would take into account the receiver and transmitter filters, and would probably be different for every TX/RX/meteor burst. My current thinking is that for the low SNRs that we are most interested in, and with the short sync words that we use, we wouldn’t be able to do a very good job of estimating the coefficients of the equalizer..." git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6776 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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Copyright (C) 2001 - 2016 by Joe Taylor, K1JT.
WSJT-X is a computer program designed to facilitate basic amateur
radio communication using very weak signals. The first four letters in
the program name stand for “Weak Signal communication by K1JT,” while
the suffix “-X” indicates that WSJT-X started as an extended (and
experimental) branch of the program WSJT.
WSJT-X Version 1.6 offers five protocols or “modes”: JT4, JT9, JT65
WSPR, and Echo. The first three are designed for making reliable QSOs
under extreme weak-signal conditions. They use nearly identical
message structure and source encoding. JT65 was designed for EME
(“moonbounce”) on the VHF/UHF bands and has also proven very effective
for worldwide QRP communication on the HF bands. JT9 is optimized for
the LF, MF, and lower HF bands. It is 2 dB more sensitive than JT65
while using less than 10% of the bandwidth. JT4 offers a wide variety
of tone spacings and has proved very effective for EME on microwave
bands up to 24 GHz. All three of these modes use one-minute timed
sequences of alternating transmission and reception, so a minimal QSO
takes four to six minutes — two or three transmissions by each
station, one sending in odd UTC minutes and the other even. On the HF
bands, world-wide QSOs are possible using power levels of a few watts
and compromise antennas. On VHF bands and higher, QSOs are possible
(by EME and other propagation types) at signal levels 10 to 15 dB
below those required for CW.
WSPR (pronounced “whisper”) stands for Weak Signal Propagation
Reporter. The WSPR protocol was designed for probing potential
propagation paths using low-power transmissions. WSPR messages
normally carry the transmitting station’s callsign, grid locator, and
transmitter power in dBm, and they can be decoded at signal-to-noise
ratios as low as -28 dB in a 2500 Hz bandwidth. WSPR users with
internet access can automatically upload their reception reports to a
central database called {wsprnet} that provides a mapping facility,
archival storage, and many other features.
Echo mode allows you to detect and measure your own lunar echoes, even
if they are far below the audible threshold.
WSJT-X provides spectral displays for passbands up to 5 kHz, flexible
rig control for nearly all modern radios used by amateurs, and a wide
variety of special aids such as automatic Doppler tracking for EME
QSOs and Echo testing. The program runs equally well on Windows,
Macintosh, and Linux systems, and installation packages are available
for all three platforms.
WSJT-X is an open-source project released under the GPL license (See
COPYING). If you have programming or documentation skills or would
like to contribute to the project in other ways, please make your
interests known to the development team. The project’s source-code
repository can be found at https://sourceforge.net/projects/wsjt, and
most communication among the developers takes place on the email
reflector https://sourceforge.net/p/wsjt/mailman. User-level
questions and answers, and general communication among users is found
on the https://groups.yahoo.com/neo/groups/wsjtgroup/info email
reflector.
Project web site:
http://www.physics.princeton.edu/pulsar/K1JT/wsjtx.html
Project mailing list (shared with other applications from the same
team):
https://groups.yahoo.com/neo/groups/wsjtgroup