// Status=review
=== Standard Exchange
By longstanding tradition, a minimally valid QSO requires the exchange
of callsigns, a signal report or some other information, and
acknowledgments.  _WSJT-X_ is designed to facilitate making such
minimal QSOs using short, structured messages. The process works best
if you use these formats and follow standard operating practices. The
recommended basic QSO goes something like this:

 CQ K1ABC FN42                          #K1ABC calls CQ
                   K1ABC G0XYZ IO91     #G0XYZ answers
 G0XYZ K1ABC –19                        #K1ABC sends report
                   K1ABC G0XYZ R-22     #G0XYZ sends R+report
 G0XYZ K1ABC RRR                        #K1ABC sends RRR
                   K1ABC G0XYZ 73       #G0XYZ sends 73

*Standard messages* consist of two callsigns (or CQ, QRZ, or DE and
one callsign) followed by the transmitting station’s grid locator, a
signal report, R plus a signal report, or the final acknowledgements
RRR or 73.  These messages are compressed and encoded in a highly
efficient and reliable way.  In uncompressed form (as displayed
on-screen) they may contain as many as 22 characters.

*Signal reports* are specified as signal-to-noise ratio (S/N) in dB,
using a standard reference noise bandwidth of 2500 Hz.  Thus, in the
example message above, K1ABC is telling G0XYZ that his
signal is 19 dB below the noise power in bandwidth 2500 Hz.  In the
message at 0004, 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, and values are significantly compressed
above about -10 dB.  JT9 supports the extended range –50 to +49 dB and
assigns more reliable numbers to relatively strong signals.

NOTE: Signals become visible on the waterfall around S/N = –26 dB and
audible (to someone with very good hearing) around –15 dB. Thresholds
for decodability are around -20 dB for FT8, -23 dB for JT4, –25 dB for
JT65, –27 dB for JT9.

NOTE: Several options are available for circumstances where fast QSOs
are desirable.  Double-click the *Tx1* control under _Now_ or _Next_
to toggle use of the Tx2 message rather than Tx1 to start a QSO.
Similarly, double-click the *Tx4* control to toggle between sending
`RRR` and `RR73` in that message.  The `RR73` message should be used
only if you are reasonably confident that no repititions will be
required.

=== Free-Text Messages

Users often add some friendly chit-chat at the end of a QSO.
Free-format messages such as "`TNX ROBERT 73`" or "`5W VERT 73 GL`"
are supported, up to a maximum of 13 characters, including spaces.  In
general you should avoid the character / in free-text messages, as the
program may then try to interpret your construction as part of a
compound callsign.  It should be obvious that the JT4, JT9, and JT65
protocols are not designed or well suited for extensive conversations
or rag-chewing.

=== Auto-Sequencing

The slow modes JT4, JT9, JT65, and QRA64 allow nearly 10 seconds at
the end of each one-minute receiving sequence -- enough time for you
to inspect decoded messages and decide how to reply.  The 15-second
T/R cycles of FT8 allow only about two seconds for this task, which is
often not enough.  For this reason a basic auto-sequencing feature is
offered. Check *Auto Seq* on the main window to enable this feature:

image::auto-seq.png[align="center",alt="AutoSeq"]

When calling CQ you may also choose to check the box *Call 1st*.
_WSJT-X_ will then respond automatically to the first decoded
responder to your CQ.

NOTE: When *Auto-Seq* is enabled the program de-activates *Enable Tx*
at the end of each QSO.  It is not intended that _WSJT-X_ should make
fully automated QSOs.

=== VHF Contest Mode

A special *NA VHF Contest* mode can be activated for FT8 and MSK144
modes by checking a box on the main window.  This mode is configured
especially for contests in which four-character grid locators are the
required exchange.  When *NA VHF Contest* mode is active, the standard
QSO sequence looks like this:

 CQ K1ABC FN42
                      K1ABC W9XYZ EN37
 W9XYZ K1ABC R FN42
                      K1ABC W9XYZ RRR
 W9XYZ K1ABC 73

In contest circumstances K1ABC might choose to call CQ again rather
than sending 73 for his third transmission.

IMPORTANT: Do not use VHF Contest Mode on an HF band or in conditions
where worldwide propagation is available.  See
<<PROTOCOL_OVERVIEW,Protocol Specifications>> for further details.

[[COMP-CALL]] 
=== Compound Callsigns

Compound callsigns such as xx/K1ABC or K1ABC/x are handled in
one of two possible ways:

.Messages containing Type 1 compound callsigns

A list of about 350 of the most common prefixes and suffixes can be
displayed from the *Help* menu.  A single compound callsign involving
one item from this list can be used in place of the standard third
word of a message (normally a locator, signal report, RRR, or 73).
The following examples are all acceptable messages containing *Type 1*
compound callsigns:

 CQ ZA/K1ABC
 CQ K1ABC/4
 ZA/K1ABC G0XYZ
 G0XYZ K1ABC/4

The following messages are _not_ valid, because a third word is not
permitted in any message containing a *Type 1* compound callsign:

 ZA/K1ABC G0XYZ -22        #These messages are invalid; each would 
 G0XYZ K1ABC/4 73          # be sent without its third "word"

A QSO between two stations using *Type 1* compound-callsign messages
might look like this:

 CQ ZA/K1ABC
                     ZA/K1ABC G0XYZ
 G0XYZ K1ABC –19
                     K1ABC G0XYZ R–22
 G0XYZ K1ABC RRR
                     K1ABC G0XYZ 73

Notice that the full compound callsign is sent and received in the
first two transmissions.  After that, the operators omit the add-on
prefix or suffix and use the standard structured messages.

.Type 2 Compound-Callsign Messages

Prefixes and suffixes _not_ found in the displayable short list are
handled by using *Type 2* compound callsigns.  In this case the
compound callsign must be the second word in a two- or three-word
message, and the first word must be CQ, DE, or QRZ.  Prefixes can be 1
to 4 characters, suffixes 1 to 3 characters.  A third word conveying a
locator, report, RRR, or 73 is permitted.  The following are valid 
messages containing *Type 2* compound callsigns:

 CQ W4/G0XYZ FM07
 QRZ K1ABC/VE6 DO33
 DE W4/G0XYZ FM18
 DE W4/G0XYZ -22
 DE W4/G0XYZ R-22
 DE W4/G0XYZ RRR
 DE W4/G0XYZ 73

In each case, the compound callsign is treated as *Type 2* because the
add-on prefix or suffix is _not_ one of those in the fixed list.  Note
that a second callsign is never permissible in these messages.

NOTE: During a transmission your outgoing message is displayed in the
first label on the *Status Bar* and shown exactly as another station
will receive it.  You can check to see that you are actually
transmitting the message you wish to send.

QSOs involving *Type 2* compound callsigns might look like either
of the following sequences:

 CQ K1ABC/VE1 FN75
                     K1ABC G0XYZ IO91
 G0XYZ K1ABC –19
                     K1ABC G0XYZ R–22
 G0XYZ K1ABC RRR
                     K1ABC/VE1 73


 CQ K1ABC FN42
                     DE G0XYZ/W4 FM18
 G0XYZ K1ABC –19
                     K1ABC G0XYZ R–22
 G0XYZ K1ABC RRR
                     DE G0XYZ/W4 73

Operators with a compound callsign use its full form when calling CQ
and possibly also in a 73 transmission, as may be required by
licensing authorities.  Other transmissions during a QSO may use the
standard structured messages without callsign prefix or suffix. 

TIP: If you are using a compound callsign, you may want to
experiment with the option *Message generation for type 2 compound
callsign holders* on the *Settings | General* tab, so that messages
will be generated that best suit your needs.

=== Pre-QSO Checklist

Before attempting your first QSO with one of the WSJT modes, be sure
to go through the <<TUTORIAL,Basic Operating Tutorial>> above as well
as the following checklist:

- Your callsign and grid locator set to correct values

- PTT and CAT control (if used) properly configured and tested

- Computer clock properly synchronized to UTC within ±1 s

- Audio input and output devices configured for sample rate 48000 Hz,
16 bits

- Radio set to *USB* (upper sideband) mode

- Radio filters centered and set to widest available passband (up to 5 kHz).

TIP: Remember that in many circumstances FT8, JT4, JT9, JT65, and WSPR
do not require high power. Under most HF propagation conditions, QRP
is the norm.
