WSJT-X/doc/user_guide/en/vhf-features.adoc

_WSJT-X_ v1.7 introduces a number of new features designed for use
on the VHF and higher bands.  These features now include:

- *JT4*, a mode particularly useful for EME on the microwave bands

- *JT9* fast modes, useful for scatter propagation on VHF bands

- *QRA64*, a mode for EME using a "`Q-ary Repeat Accumulate`" code,
a low-density parity-check (LDPC) code using a 64-character symbol
alphabet

- *MSK144*, a mode for meteor scatter using a binary LDPC code and
Offset Quadrature Phase-Shift Keying (OQPSK).  The resulting waveform
is sometimes called Minimum Shift Keying (MSK).

- *ISCAT*, intended for aircraft scatter and other types of scatter
propagation

- *Echo* mode, for detecting and measuring your own lunar echoes

- *Doppler tracking*, which becomes increasingly important for EME
on bands above 1.2 GHz.

- *Auto-sequencing* of transmitted messages for the fast modes with
forward error control

[[VHF_SETUP]]
=== VHF Setup

To activate the VHF-and-up features:

- On the *Settings | General* tab check *Enable VHF/UHF/Microwave
features* and *Single decode*.

- For EME, check *Decode at t = 52 s* to allow for extra path delay on
received signals.

- If you will use automatic Doppler tracking and your radio accepts
frequency-setting commands while transmitting, check *Allow Tx
frequency changes while transmitting*.  Transceivers known to permit
such changes include the IC-735, IC-756 Pro II, IC-910-H, FT-817,
FT-847, FT-857, FT-897, TS-590S, TS-590SG, TS-2000 (with Rev 9 or
later firmware upgrade), Flex 1500 and 5000, HPSDR, Anan-10, Anan-100,
and KX3.

IMPORTANT: If your radio does not accept commands to change frequency
while transmitting, Doppler tracking will be approximated with a
single Tx frequency adjustment before a transmission starts, using a
value computed for the middle of the Tx period.

- On the *Radio* tab select *Split Operation* (use either *Rig* or
*Fake It*; you may need to experiment with both options to find one
that works best with your radio).

- On the right side of the main window select *Tab 1* to present the
traditional format for entering and choosing Tx messages.

The main window will reconfigure itself as necessary to display
controls supporting the features of each mode.

- If you are using transverters, set appropriate frequency offsets on
the *Settings | Frequencies* tab.  Offset is defined as (transceiver
dial reading) minus (on-the-air frequency).  For example, when using a
144 MHz radio at 10368 MHz, *Offset (MHz)* = (144 - 10368) =
-10224.000.  If the band is already in the table, you can edit the
offset by double clicking on the offset field itself.  Otherwise a new
band can be added by right clicking in the table and selecting
*Insert*.

image::Add_station_info.png[align="center",alt="Station information"]

- On the *View* menu, select *Astronomical data* to display a window
with important information for tracking the Moon and performing
automatic Doppler control.  The right-hand portion of the window
becomes visible when you check *Doppler tracking*.

image::Astronomical_data.png[align="center",alt="Astronomical data"]

Three different types of Doppler tracking are provided:

- Select *Full Doppler to DX Grid* if you know your QSO partner's locator
and he/she will not be using any Doppler control.

- Select *Receive only* to enable EME Doppler tracking of your receive
frequency to a specific locator. Your Tx frequency will remain fixed.

- Select *Constant frequency on Moon* to correct for your own one-way
Doppler shift to or from the Moon.  If your QSO partner does the same
thing, both stations will have the required Doppler compensation.
Moreover, anyone else using this option will hear both of you
without the need for manual frequency changes.

- See <<ASTRODATA,Astronomical Data>> for details on the quantities
displayed in this window.

=== JT4

JT4 is designed especially for EME on the microwave bands, 2.3 GHz and
above.

- Select *JT4* from the *Mode* menu.  The central part of the main
window will look something like this:

image::VHF_controls.png[align="center",alt="VHF Controls"]

- Select the desired *Submode*, which determines the spacing of
transmitted tones. Wider spacings are used on the higher microwave
bands to allow for larger Doppler spreads. For example, submode JT4F
is generally used for EME on the 5.7 and 10 GHz bands.

- For EME QSOs some operators use short-form JT4 messages consisting
of a single tone.  To activate automatic generation of these messages,
check the box labeled *Sh*.

- Select *Deep* from the *Decode* menu.  You may also choose to *Enable
averaging* over successive transmissions and/or correlation decoding,
*Enable deep Search*.

image::decoding_depth.png[align="center",alt="Decoding Depth"]

IMPORTANT: Additional hints for using JT4 and Echo mode on the
*EME path have been compiled by G3WDG and are available here: {jt4eme}.

=== JT65

In most ways JT65 operation on VHF and higher bands is similar to HF
usage.  However, a few differences should be noted.  Typical VHF/UHF
operation involves only a single signal in the receiver passband, or
perhaps a few, rather than many.  Normally it's best to check *Single
decode* on the *Settings -> General* tab and uncheck *Two pass
decoding* on the *Advanced* tab.  In this mode the JT65 decoder will
respond to special message formats sometimes used for EME, including
the OOO signal report and shorthand messages for RO, RRR, and 73.
Those messages will be automatically generated if you check the
shorthand message box *Sh*.

As for JT4, you should check *Deep* on *the *Decode* menu, and
optionally *Enable averaging* and *Deep search*.


=== QRA64

QRA64 is an experimental mode in the present alpha release of
_WSJT-X_, Version 1.7.  The protocol is still subject to change, and
some features of the decoder will likely change.  In most ways
operation of QRA64 is similar to JT65.

=== ISCAT

ISCAT is a useful mode for signals that are weak but more or less
steady in amplitude, at least for several seconds.  Aircraft scatter
at 10 GHz is a good example.  ISCAT messages are free-format and may
have any length from 1 to 28 characters.  The protocol includes no
error-correction facility.

=== MSK144

Meteor-scatter QSOs can be made any time on the VHF bands at distances
up to about 2100 km (1300 miles).  Completing a QSO takes longer in
the evening than in the morning, longer at higher frequencies, and
longer at distances close to the upper limit.  But with patience, 
100 Watts or more, and a single yagi it can usually be done.

Unlike other _WSJT-X modes, MSK144 decodes received signals in real
time.  Decoded messages will appear on your screen almost as soon as
you hear them.

- Select *MSK144* from the *Mode* menu.

- Select *Fast* from the *Decode* menu.

- Set the audio receiving frequency to *Rx 1500 Hz*.

- Set frequency tolerance to *F Tol 100*.

- Set the *T/R* sequence duration to 15 s.

- To match decoding depth to your computer's capability, click
*Monitor* (if it's not already green) to start a receiving sequence
and observe the percentage of CPU usage displayed on the _Receiving_
label in the Status Bar:

image::Rx_pct_MSK144.png[align="center",alt="MSK144 Percent CPU"]

- The displayed number (here 17%) indicates the fraction of CPU
capability used being used by the MSK144 real-time decoder.  If it is
well below 100% you may increase the decoding depth from *Fast*
to *Normal* or *Deep*, and increase *F Tol* from 100 to 200 Hz.

IMPORTANT: Most modern multi-core computers can easily handle the
optimum parameters *Deep* and *F Tol 200*.  Slower machines may not be
able to keep up at these settings; in that case there will be a modest
loss in decoding capability for the weakest pings.

- T/R sequences of 15 seconds or less requires choosing your
transmitted messages very quickly.  Check *Auto Seq* to have the
computer make the necessary decisions automatically, based on received
messages.

For operation at 144 MHz or above you may find it helpful to use
short-format messages for Tx3, Tx4, and Tx5.  These messages are 20 ms
long, compared with 72 ms for full-length MSK144 messages.  Their
information content is a 12-bit hash of the two callsigns, rather than
the callsigns themselves, plus a 4-bit report, acknowledgment, or
sign-off.  Only the intended recipient can decode short-messages.

- Check *Sh* to enable short messages.

IMPORTANT: There is little or no advantage to using MSK144 *Sh*
messages at 50 or 70 MHz.  At these frequencies most pings are long
enough to support standard messages.

=== Echo Mode

*Echo* mode allows you to make sensitive measurements of your own
lunar echoes even when they are too weak to be heard. Select *Echo*
from the *Mode* menu, aim your antenna at the moon, pick a clear
frequency, and toggle click *Tx Enable*. _WSJT-X_ will then cycle
through the following loop every 6 seconds:

1. Transmit a 1500 Hz fixed tone for 2.3 s
2. Wait about 0.2 s for start of the return echo
3. Record the received signal for 2.3 s
4. Analyze, average, and display the results
5. Repeat from step 1

To make a sequence of echo tests:

- Select *Echo* from the *Mode* menu.

- Check *Doppler tracking* and *Constant frequency on the Moon* on the
Astronomical Data window.

- Be sure that your rig control has been set up for _Split Operation_,
using either *Rig* or *Fake It* on the *Settings | Radio* tab.

- Click *Enable Tx* on the main window to start a sequence of 6-second
cycles.

- _WSJT-X_ calculates and compensates for Doppler shift automatically.
Your return echo should always appear at the center of the plot area
on the Echo Graph window, as in the screen shot below.

image::echo_144.png[align="center",alt="Echo 144 MHz"]