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

=== VHF Setup

_WSJT-X_ v1.7 builds on the features for VHF and higher bands first
introduced in v1.6.  These features now include:

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

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

- *MSK144*, a mode for meteor scatter using a binary LDPC code and
Offset Quadrature Phase-Shift Keying (OQPSK), a waveform also
describable as 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

- Automatic *Doppler tracking* for the EME path.  This is increasingly
important on bands above 1.2 GHz.

- Optional *Auto-sequencing* of messages for the fast modes.

To activate the VHF-and-up features:

- Check the box labeled *Enable VHF/UHF/Microwave features* on the
*Settings | General* tab.

- In most cases you will also want to check *Single decode*.

- If you will be doing EME, check the box *Decode at t = 52 s*
to allow for the EME path delay on received signals.

- If you will use automatic Doppler tracking and your radio accepts
QSY commands while transmitting, check the box *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 firmware upgrade), Flex
1500 and 5000, HPSDR, Anan-10, Anan-100, and KX3. 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).

- 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 transmitting, using a value computed
for the middle of the Tx period.

- The main window will reconfigure itself as necessary to display
controls supporting the features of each mode.  For example, in JT4 mode
the central part of the main window might look something like this:

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

- 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.  Check the box labeled *Doppler tracking*
to ensure that the right-hand portion of the window is visible.

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.  The hypothetical "`man
in the moon`" would copy all of you on the selected nominal frequency.

- In the example depicted above, the moon-based nominal frequency is
100 kHz above the stated band edge, or 10368.100 MHz for the 10 GHz
band.  The home station two-way self Doppler shift is +24366 Hz, so the
one-way shift is +12183 Hz.  Therefore, the receive frequency is set
to 10,360.112183 Hz.  When a transmission is started, the frequency
will be reset to 12183 Hz _below_ the nominal on-the-moon frequency.

=== EME with JT4

- Select *JT4* from the *Mode* menu.

- Select the desired submode, which determines the tone spacing.
Higher 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 10 GHz band.

- The JT4 decoder in _WSJT-X_ includes optional capabilities for
averaging over successive transmissions, and correlation decoding,
also known as "`Deep Search`".  Either or both of these options may
be selected from the *Decode* menu.

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

- By convention, EME with JT4 can use "`short form`" messages
consisting of a single tone.  To activate automatic generation of
these messages, check the box labeled *Sh* on the main window.

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

=== EME with JT65

TBD ...

=== EME with QRA64

TBD ...

=== 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"]