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 partity-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:

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

- For EME, check *Decode at t = 52 s* to allow for the 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 by making 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).

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 is
invisible until 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.

=== JT4

JT4 is highly effective 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,
also known as "`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, but a few differences should be noted.  Checking the box
*Enable VHF/UHF/Microwave features* on the *Settings -> General* tab
causes several additional user controls to be displayed.  The decoder
will respond to special message formats used particularly for EME,
including the OOO signal report and shorthand messages for RO, RRR,
and 73.  Typical operation at VHF and UHF involves only a single
signal in the receiver passband, rather than many.  It's usually best
then to check the *Single decode* box on the *Settings -> General*
tab.

=== QRA64

QRA64 is present as an experimental mode in the present alpha release
of _WSJT-X_, Version 1.7.  Operation is basically similar to JT65.

=== Meteor Scatter with MSK144

Meteor-scatter QSOs can be made at any time on the VHF bands, at
distances up to about 2100 km or 1300 miles.  Completing a QSO takes
longer in the evening than in the morning, longer at 144 MHz than at
50 MHz, and longer at 2000 km than 1500 km; but with patience, at
least 100 Watts, and a single yagi it can usually be done.

- Select *Tab 1* to present the traditional format for selecting Tx
messages.

- Select *MSK144* from the *Mode* and *Fast* from the *Decode* menu.

- Set the audio receiving frequency to *Rx 1500 Hz*, frequency
tolerance to *F Tol 100*, and T/R sequence duration to 15 s.

- MSK144 does decodes received signals in real time, so you can see
decoded messages almost as soon as you hear them.  To match decoding
depth to your computer's capability, click *Monitor* (if
necessary) 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"]

- This number (here 17%) measures the fraction of CPU capability used
being used by the MSK144 real-time decoder.  If it is well below, say,
80% 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 these
maximum parameters, but some slower machines may not be able to keep
up.  In that case there will be some loss in decoding capability for
the weakest pings.

- You may now proceed to make QSOs using essentially the same
procedures described in <<MAKE_QSOS,Making QSOs>>.

- T/R sequences of 15 seconds or less make it sometimes desirable to
switch transmitted messages very quickly.  Check the *Auto Seq* box
to have the computer make the necessary decisions automatically.

- For operation at 144 MHz or above, you might choose to use the
MSK144 short-format messages for Tx3, Tx4, and Tx5.  Check the box
labeled *Sh* to enable this feature.  (There is little need for this
option at 50 or 70 MHz, where most pings are long enough to support
the standard MSK144 message length.)

=== Scatter Propagation with ISCAT

TBD ...

=== 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.

- On the Astronomical Data window check *Doppler tracking* and
*Constant frequency on the Moon*

- Choose your desired test frequency using the *Frequency above nominal
band edge* controls.

- Be sure that your rig control has been set up for _Split Operation_
(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"]