FST4W is used in the same way as WSPR, but FST4W has significant
advantages for use on the 2200 m and 630 m bands.  By default the
central *Rx Freq* is 1500 Hz and *F Tol* is 100 Hz, so the active
decoding range is 1400 to 1600 Hz.  However, for added flexibility you
can select different center frequencies and *F Tol* values.  We expect
that usage conventions will soon be established for FST4W activity on
2200 and 630 m.

A new drop-down control below *F Tol* offers a round-robin mode for
scheduling FST4W transmissions:

image::FST4W_RoundRobin.png[align="center"]

If three operators agree in advance to select the options *1/3*,
*2/3*, and *3/3*, for example, their FST4W transmissions will occur in
a fixed sequence with no two stations transmitting simultaneously.
Sequence 1 is the first sequence after 00:00 UTC.  For WSPR-like
scheduling behavior, you should select *Random* with this control.

.Open a Wave File:

- Select *FST4W* on the *Mode* menu. Set *T/R* to 1800 s and *Decode | Deep*.
- Select appropriate wide graph settings. For example, try *Bins/Pixel* 1, 
*Start* 1200 Hz and *N Avg* 150. 
- Enable the multi-threshold noise blanker by setting the noise blanker *NB* to -1. 
This setting tells the decoder to try 0, 5, 10, 15, and 20 % blanking.
The *NB* setting is located just above the green receive power indicator and below the 
frequency selection menu.
- Open a sample Wave file using *File | Open* and select the file
...\save\samples\FST4+FST4W\210203_0600.wav. Processing may take a minute or
more because of the noise blanker setting. When it is finished you should 
see a single decode as shown in the screenshot:

image::FST4W-1.png[align="left"]
image::FST4W-2.png[align="left"]

The weak signal associated with the single decode is all but invisible on the 
widegraph spectrogram. Note that the sample wave file will not decode if 
the noise blanker is turned off
(*NB* set to 0 %) or if it is set to any positive number less than 14 %. Using 
*NB* -1 tells WSJT-X to try noise blanker settings 0, 5, 10, 15, and 20 %. Similarly,
*NB* -2 tells WSJT-X to try noise blanker settings 0, 2, 4, 6, ..., 20 %.
