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[[VHF_SETUP]]
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=== VHF Setup
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_WSJT-X_ v1.7 builds on the features for VHF and higher bands first
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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 --
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a low-density partity-check (LDPC) code with a 64-character symbol
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alphabet
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- *MSK144*, a mode for meteor scatter using a binary LDPC code and
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Offset Quadrature Phase-Shift Keying (OQPSK), a waveform also
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describable as Minimum Shift Keying (MSK)
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- *ISCAT*, intended for aircraft scatter and other types of scatter
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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. This is increasingly
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important on bands above 1.2 GHz.
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- Optional *Auto-sequencing* of messages for the fast modes.
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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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frequency-setting commands while transmitting, check the box *Allow Tx
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frequency changes while transmitting*. Transceivers known to permit
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such changes include the IC-735, IC-756 Pro II, IC-910-H, FT-817,
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FT-847, FT-857, FT-897, TS-590S, TS-590SG, TS-2000 (with Rev 9
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firmware upgrade), Flex 1500 and 5000, HPSDR, Anan-10, Anan-100, and
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KX3. On the *Radio* tab select *Split Operation* (use either *Rig* or
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*Fake It*; you may need to experiment with both options to find one
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that works best with your radio).
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- If your radio does not accept commands to change frequency while
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transmitting, Doppler tracking will be approximated by making a single
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Tx frequency adjustment before a transmission starts, using a value
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computed for the middle of the Tx period.
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- The main window will reconfigure itself as necessary to display
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controls supporting the features of each mode. For example, in JT4 mode
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the central part of the main window looks something like this:
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image::VHF_controls.png[align="center",alt="VHF Controls"]
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- If you are using transverters, set appropriate frequency offsets on
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the *Settings | Frequencies* tab. Offset is defined as (transceiver
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dial reading) minus (on-the-air frequency). For example, when using a
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144 MHz radio at 10368 MHz, *Offset (MHz)* = (144 - 10368) =
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-10224.000. If the band is already in the table, you can edit the
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offset by double clicking on the offset field itself. Otherwise a new
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band can be added by right clicking in the table and selecting
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*Insert*.
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image::Add_station_info.png[align="center",alt="Station information"]
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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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=== 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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- The JT4 decoder in _WSJT-X_ includes optional capabilities for
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averaging over successive transmissions, and 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: Additional hints for using JT4 and Echo mode on the
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EME path have been compiled by G3WDG and are available here: {jt4eme}.
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=== JT65
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In most ways JT65 operation on VHF and higher bands is similar to HF
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usage, but a few differences should be noted. Checking the box
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*Enable VHF/UHF/Microwave features* on the *Settings -> General* tab
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causes several additional user controls to be displayed. The decoder
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will respond to special message formats used particularly for EME,
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including the OOO signal report and shorthand messages for RO, RRR,
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and 73. Typical operation at VHF and UHF involves only a single
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signal in the receiver passband, rather than many. It's usually best
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then to check the *Single decode* box on the *Settings -> General*
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tab.
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=== QRA64
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QRA64 is present as an experimental mode in the present alpha release
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of _WSJT-X_, Version 1.7. Operation is basically similar to JT65.
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=== Meteor Scatter with MSK144
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Meteor-scatter QSOs can be made at any time on the VHF bands, at
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distances up to about 2100 km or 1300 miles. Completing a QSO takes
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longer in the evening than in the morning, longer at 144 MHz than at
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50 MHz, and longer at 2000 km than 1500 km; but with patience, at
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least 100 Watts, and a single yagi it can usually be done.
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- Select *Tab 1* to present the traditional format for selecting Tx
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messages.
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- Select *MSK144* from the *Mode* and *Fast* from the *Decode* menu.
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- Set the audio receiving frequency to *Rx 1500 Hz*, frequency
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tolerance to *F Tol 100*, and T/R sequence duration to 15 s.
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- MSK144 does decodes received signals in real time, so you can see
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decoded messages almost as soon as you hear them. To match decoding
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depth to your computer's capability, click *Monitor* (if
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necessary) to start a receiving sequence, and observe the percentage
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of CPU usage displayed on the _Receiving_ label in the Status Bar:
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image::Rx_pct_MSK144.png[align="center",alt="MSK144 Percent CPU"]
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- This number (here 17%) measures the fraction of CPU capability used
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being used by the MSK144 real-time decoder. If it is well below, say,
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80% you may increase the decoding depth from *Fast* to *Normal* or
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*Deep*, and increase *F Tol* from 100 to 200 Hz.
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IMPORTANT: Most modern multi-core computers can easily handle these
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maximum parameters, but some slower machines may not be able to keep
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up. In that case there will be some loss in decoding capability for
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the weakest pings.
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- You may now proceed to make QSOs using essentially the same
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procedures described in <<MAKE_QSOS,Making QSOs>>.
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- T/R sequences of 15 seconds or less make it sometimes desirable to
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switch transmitted messages very quickly. Check the *Auto Seq* box
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to have the computer make the necessary decisions automatically.
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- For operation at 144 MHz or above, you might choose to use the
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MSK144 short-format messages for Tx3, Tx4, and Tx5. Check the box
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labeled *Sh* to enable this feature. (There is little need for this
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option at 50 or 70 MHz, where most pings are long enough to support
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the standard MSK144 message length.)
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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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