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166 lines
6.2 KiB
Plaintext
166 lines
6.2 KiB
Plaintext
=== VHF Setup
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_WSJT-X_ v1.7 builds on for VHF and
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higher bands first introduced in v1.6. These features now include:
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- *JT4*, a mode particularly useful for EME on the microwave bands
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- *QRA64*, a mode for EME using a "`Q-ary Repeat Accumulate`" code, a
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low-density partity-check (LDPC) code using a 64-character symbol
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alphabet
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- *MSK144*, a mode for meteor scatter using a binary LDPC code
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and Offset Quadrature Phase-Shift Keying (OQPSK), a waveform also
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known as Minimum Shift Keying (MSK)
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- *ISCAT*, intended for other types of scatter propagation.
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- *Echo* mode, for detecting and measuring your own lunar echoes
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- Automatic *Doppler tracking* for the EME path
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To activate the VHF-and-up features:
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- Check the box labeled *Enable VHF/UHF/Microwave features* on the
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*Settings | General* tab.
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- In most cases you will also want to check *Single decode*.
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- If you will be doing EME, check the box *Decode at t = 52 s*
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to allow for the EME path delay on received signals
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- If you will use automatic Doppler tracking and your radio accepts
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QSY commands while transmitting, check the box *Allow Tx frequency
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changes while transmitting*. Transceivers that allow such changes
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include the IC-735, IC-756 Pro II, IC-910-H, FT-817, FT-847, FT-857,
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FT-897, TS-590S, TS-590SG, TS-2000 (with Rev 9 firmware upgrade), Flex
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1500 and 5000, HPSDR, Anan-10, Anan-100, and KX3. On the *Radio* tab
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select *Split Operation* (use either *Rig* or *Fake It*; you may need
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to experiment with both options to find one that works best with your
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radio).
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- If your radio does not accept commands to change frequency while
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transmissing, Doppler tracking is accomplished by making a single Tx
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frequency adjustment before transmitting, using a value computed for
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the middle of the Tx period.
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- The main window reconfigures itself as necessary to include controls
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supporting features of each mode. For example, in JT4 mode the
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central part of the main window might look something like this:
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image::VHF_controls.png[align="center",alt="VHF Controls"]
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- On the *View* menu, select *Astronomical data* to display a window
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with important information for tracking the Moon and performing
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automatic Doppler control. Check the box labeled *Doppler tracking*
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to ensure that the right-hand portion of the window is visible.
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image::Astronomical_data.png[align="center",alt="Astronomical data"]
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Three different types of Doppler tracking are provided:
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- Select *Full Doppler to DX Grid* if you know your QSO partner's locator
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and he/she will not be using any Doppler control.
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- Select *Receive only* to enable EME Doppler tracking of your receive
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frequency to a specific locator; your Tx frequency will remain fixed.
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- Select *Constant frequency on Moon* to correct for your own (one-way)
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Doppler shift to or from the Moon. If your QSO partner does the same
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thing, both stations will have the required Doppler compensation.
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Moreover, anyone else using this option will hear both of you
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without the need for manual frequency changes. The hypothetical "`man
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in the moon`" would copy all of you on the selected nominal frequency.
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- In the example depicted above, the moon-based nominal frequency is
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100 kHz above the stated band edge, or 10368.100 MHz for the 10 GHz
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band. The home station two-way self Doppler shift is +24366 Hz, so the
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one-way shift is +12183 Hz. Therefore, the receive frequency is set
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to 10,360.112183 Hz. When a transmission is started, the frequency
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will be reset to 12183 Hz _below_ the nominal on-the-moon frequency.
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=== EME with JT4
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- Select *JT4* from the *Mode* menu.
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- Select the desired submode, which determines the tone spacing.
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Higher spacings are used on the higher microwave bands, to allow for
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larger Doppler spreads. For example, submode JT4F is generally used
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for EME on the 10 GHz band.
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- If using a transverter, set the appropriate offset on the *Settings
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| Frequencies* tab. Offset is defined as (transceiver dial reading)
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minus (on-the-air frequency). For example, when using a 144 MHz radio
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at 10368 MHz, *Offset (MHz)* = (144 - 10368) = -10224.000. If the
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band is already in the table, you can edit the offset by double
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clicking on the offset field itself. Otherwise a new band can be
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added by right clicking in the table and selecting *Insert*.
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image::Add_station_info.png[align="center",alt="Station information"]
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- The JT4 decoder in _WSJT-X_ includes optional facilities for
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averaging over successive transmissions and also correlation decoding,
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also known as "`Deep Search`". Either or both of these options may
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be selected from the *Decode* menu.
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image::decoding_depth.png[align="center",alt="Decoding Depth"]
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- By convention, EME with JT4 can use "`short form`" messages
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consisting of a single tone. To activate automatic generation of
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these messages, check the box labeled *Sh* on the main window.
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IMPORTANT: Thanks to G3WDG, many additional hints for using JT4 and
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Echo mode on the EME path are available in {jt4eme}.
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=== EME with JT65
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TBD ...
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=== EME with QRA64
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TBD ...
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=== Meteor Scatter with MSK144
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TBD ...
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=== Scatter Propagation with ISCAT
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TBD ...
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=== Echo Mode
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*Echo* mode allows you to make sensitive measurements of your own
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lunar echoes, even when they are too weak to be heard. Select *Echo*
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from the *Mode* menu, aim your antenna at the moon, pick a clear
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frequency, and toggle click *Tx Enable*. _WSJT-X_ will then cycle
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through the following loop every 6 seconds:
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1. Transmit a 1500 Hz fixed tone for 2.3 s
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2. Wait about 0.2 s for start of the return echo
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3. Record the received signal for 2.3 s
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4. Analyze, average, and display the results
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5. Repeat from step 1
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To make a sequence of echo tests:
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- Select *Echo* from the *Mode* menu.
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- On the Astronomical Data window check *Doppler tracking* and
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*Constant frequency on the Moon*
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- Choose your desired test frequency using the *Frequency above nominal
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band edge* controls.
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- Be sure that your rig control has been set up for _Split Operation_
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(either *Rig* or *Fake It*) on the *Settings | Radio* tab.
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- Click *Enable Tx* on the main window to start a sequence of 6-second
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cycles.
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- _WSJT-X_ calculates and compensates for Doppler shift automatically.
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Your return echo should always appear at the center of the plot area
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on the Echo Graph window, as in the screen shot below.
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image::echo_144.png[align="center",alt="Echo 144 MHz"]
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