Operating Controls & Displays




The main display for fldigi is the waterfall display shown above in color and in scale x1.  The button toggles between color and b/w display in the waterfall.  The button Wtr toggles the display between a waterfall and a spectrum display.  Holding the shift key down and pressing this button will change the waterfall display to an oscilloscope display of the received audio signal.  Let the mouse cursor hover over any one of the controls and a small hint box will open to help you navigate the various controls.  The Norm button controls the speed of the waterfall drop.  Three speeds are available, SLOW, NORM and FAST.  The load on the cpu will be directly proportional to this selection.  If your cpu is slow you might want to select the SLOW option for the waterfall.

The scale control (X1, X2, X4) expands or contracts the view into the fast fourier transform that is displayed on the waterfall or the FFT display.  fldigi always computes the FFT to a 1 Hz resolution, and displays the results according to the scale control.

X1 scale X2 scale X4 scale

The next three controls are positional conrols for the waterfall.  The waterfall can display 4096 data points, where each one can be thought of as a spectral line at the equivalent Hertz.  The ratio is actually 8000/8192 and is related to the ratio of sound card sampling rate to Fast Fourier Transform length.  This ratio changes for some modems that require a sampling rate other than 8000 Hz.  The left arrow key will shift the display to the right (displays a lower section of the spectrum).  The right arrow key moves the display higher in frequency.  These two buttons are repeating buttons.  Hold them down and the display slews at about 20 shifts / sec.  The center button with the two vertical block lines is a "center the signal" button.  The current cursor (red signal cursor in the waterfall) will be centered in the display area.

Try moving the cursor around in the waterfall area.  You will see a set of yellow cursor blocks that show the center point and bandwidth of the current operating mode (psk31 = 31.25 Hz for example).  To capture a received signal just click near the signal and the AFC will perform a multi-step acquisition.  This will be very fast and should not require additional operator intervention.  Casual tuning  You can take a look at any received signal on the waterfall by right-clicking and holding the mouse button on or near the signal.  The modem will begin to decode that signal if it is in the currently selected mode.  The text will be a unique color on the Rx text widget so that you can discern the difference between casual and normal tracking.  Release the mouse button and the tracking returns to the previously selected normal tracking point.

The next control is your transceive audio frequency.  In the display above you can see that the audio signal is 1679 Hz.  The red cursor is centered beneath 14071.679 Mhz.  The transceiver was set to 14070 Mhz.  The arrow key pairs move up/down in cycles and tens of cycles.  You can fine tune the receive point using this control.

The next two controls to the right of the audio frequency control are for the receive signal processing.  The one that reads -10 is the max signal level for the waterfall/spectrum display.  The one that reads 51 is for the range over which that control will display signals.  Both of these are in dB.  The default of -10 / 40 is a good starting point, but you need to adjust these for band conditions.  You can see the impact of these controls most easily by putting the main display area in the spectrum mode.  Changes in these controls will effect the waterfall instantly and for all past history displayed on the waterfall.  You do not have to wait for new signal data to observe the effect.

The QSY button is very specific to rigs interfaced with either hamlib or the memory mapped i/o.  Each rig has a sweet spot associated with its bandwidth controller.  For the Argonaut V this is 1100 Hz.  For the the Kachina it is 1000 Hz.  As the transceivers bandwidth is changed the changes occur centered at this frequency.  So ....  let's say that I just started copying a rare dx at 1758 Hz and I wanted to put the signal at the sweet spot so I could easily narrow the receiver bandwidth.  Click on the signal on the waterfall.  Let the AFC capture and then press the QSY button.  The tranceiver frequency will be shifted and the fldigi audio tracking point shifted in unison such that the signal is now at the receivers sweet spot.  Very fast and very convenient!  If you do not have hamlib enabled for your transceiver this button will be dimmed and not activated.

The T/R button should be self-explanatory.  It's your transmit/receive button.  Action is immediate, so if your were transmiting some text and hit the button the PTT is disabled, the transmit text area cleared and the program returned to receive mode.  The T/R button is a "lighted button" that shows RED when transmitting.  All other lighted buttons show YELLOW when they are in the active state.

The Lck button locks the transmit audio frequency to its present value.  You can then continue to QSY around your transmit position.  I have used this to reply to a DX station that wanted a +500 Hz  response.  The DX was at 690 Hz audio, and wanted a response at +500.  I moved the display cursor (or the audio frequency control) to 1190 Hz.  Hit the Lck button and then went back to 690 with the waterfall cursor.  Now the program is receiving on 690 Hz and transmitting on 1190 Hz.  Caught him on the first try.  Use this button also as a Master Station control.  Not all rigs are equal in their VFO performance.  Some exhibit a shift between receive and transmit.  If this occurs then the stations find themselves chasing each other with every t/r exchange.  Locking your transmit frequency with this control will inhibit that from happening.  Be sure to disable the control when that qso is over or you may forget and transmit over top of another qso!

If the "Lck" is enabled the TX frequency does not follow the AFC action applied to the RX frequency.

For transceivers which are either hamlib or memmap enabled, if the "Qsy" button is pressed BOTH the RX and TX frequencies are changed to synchronize to where the RX was positioned.

Perhaps some numbers will help to make that a little clearer.

"Lck"
Before "Qsy"

After "Qsy"


RX
TX
RX
TX
OFF
1002 / 7071.002
1002 / 7071.002
1500 / 7071.002
1500 / 7071.002
ON
1002 / 7071.002
1000 / 7071.000
1500 / 7071.002
1500 / 7071.002
ON
1000 / 7071.000
1800 / 7071.800
1500 / 7071.000
1500 / 7071.000

With "Lck" off the TX audio frequency always always synchronized with the RX frequency.

With "Lck" on the TX audio frequency is fixed with respect to the RX frequency UNLESS the "Qsy" button is pressed in which case it shifts to the RX frequency, the Transceiver VFO is shifted and both the RX and TX audio frequencies are shifted to put both into the middle of the transceiver passband.  The TX continues to be locked, but at the new audio frequency.

If the "Lck" is ON moving the cursor around will ONLY EFFECT the RX frequency and NOT the TX frequency.

The AFC and SQL buttons enable or disable the respective function in the software.  The slider just above the AFC & SQL controls is the squelch level control.  The bar indicator just above it is the equivalent of received signal level and relates on a 1:1 basis with the squelch level slider.

The indicator just to the left of the AFC button is the overload indicator.  It will flash red if your audio drive to sound card is marginally too high and turn red when it is in overload.  Back down the mixer control or the audio pad from the rig to computer.  Fldigi will not perform well if the sound card is over driven.  You will see ghost signals on the waterfall and the modem decoders will not work correctly.

Tuning and Setting the Audio Drive Signal Level


Sound Card Select
Mixer Setup

Rcv / Xmt Level
   
Too often you see an overdriven signals on the digital sub-bands; multiple audio sidebands on PSK, splatter from overdriven MFSK and RTTY.  There is absolutely no reason for a transceiver driven by fldigi to exhibit this type of performance.  You can set up your computer / transceiver for good solid performance without excessive drive.

The "Tune" menu button on the main menu system provides a continuous tone audio at the exact frequency to which the waterfall cursor has been set.  The peak amplitude of this signal is the peak amplitude of every modem signal generated by fldigi.  None will exceed this value, even the simultaneous multi-tone modes like Throb.  Every modern SSB transmitter uses some automatic level control ALC for preventing overdrive for SSB voice.  A little overdrive on a voice channel can be tolerated to a degree.  In fact, that is what an analog RF compressor does, overdrive and then subsequent filtering.  But you absolutely cannot tolerate that with the digital modes.  Here is the way to set up your transceiver for a clean signal.  I recommend starting out with a dummy load, but an "off hour" for a band might work just as well if you do not have a dummy load.
You should try the the above adjustments at different audio frequencies.  Transceivers that achieve the SSB filtering with crystal or mechanical filters will have a considerable amount of variation across the passband of the filter.  This will show up as a varying amount of ALC that is dependent on the audio frequency.  Once you are comfortable with the process you can very quickly repeat the "Tune" and set the power for the frequency to which the waterfall is set.

Receive audio level should be adjusted so that the overload indicator to the left of the AFC button does not illuminate red.  When observing the received signals on the oscilloscope view you should expect that they do not exceed a peak-to-peak amplitude of 3/4 of the full display height.


Menu