Hi, Recently upgraded to GRC 3.7 (from 3.6.5). The QT GUI Sink Frequency Display: Center Frequency (Hz) control and the 'Display RF Frequencies' checkbox do not seem to be operating correctly in GRC 3.7.
In GRC 3.6, Center Frequency (on the block properties) had no effect on the actual display. If a value was entered in Center Frequency (Hz), there was no change to the display at all. If the 'Display RF Frequencies' checkbox was checked and a non-zero value was in the Center Frequency (Hz) block, then the display did not change, but the X-Axis labels were changed to the sum of (display + Center Frequency). I think this agrees with the documentation. This was very useful for example as the NCO frequency of a down-converting receiver could be entered in the Center Frequency box, and when 'Display RF Frequencies' box was checked, the frequency display would show the actual RF frequency of the signal prior to downconversion. Searching the discuss-gnuradio archives on the topic revealed the last post on this topic in 2011, and that this seemed to be the intended operation of the controls. In GRC 3.7 however it does not work this way. Placing a value in Center Frequency (Hz) shifts the graphical display. If Center Frequency has a value greater than the display width, then in fact nothing at all is displayed on the graph (it would all be shifted past the right side). The X-Axis labels are altered whether or not the Display RF Frequencies checkbox is selected. For example: a 10 KHz complex waveform shows a single peak at 10 KHz when Center Frequency = 0. But if Center Frequency = 10000 is selected (Display RF = off), then the single peak is shifted to the right on the display, and appears over the 20000 Hz indicator. The display range is labeled -6 to +26 KHz. For the above, when Display RF Frequencies is selected, the X-Axis displays +5 to +15 KHz, and the single peak shows at a frequency of 11.56 KHz. I've tried to think of the ways that these controls might have been repurposed, but can't come up with a combination that would give this behavior, so assume that it may be a bug. The way it worked in GRC 3.6 would be desired behavior. Below is the simple GRC 3.7 flowgraph to demonstrate: (Signal Source (complex) -> throttle (complex) -> QT GUI Sink (complex)). Thanks. -- Tom, N5EG <?xml version='1.0' encoding='ASCII'?> <flow_graph> <timestamp>Tue Aug 13 05:53:25 2013</timestamp> <block> <key>options</key> <param> <key>id</key> <value>top_block</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>title</key> <value></value> </param> <param> <key>author</key> <value></value> </param> <param> <key>description</key> <value></value> </param> <param> <key>window_size</key> <value>1280, 1024</value> </param> <param> <key>generate_options</key> <value>qt_gui</value> </param> <param> <key>category</key> <value>Custom</value> </param> <param> <key>run_options</key> <value>prompt</value> </param> <param> <key>run</key> <value>True</value> </param> <param> <key>max_nouts</key> <value>0</value> </param> <param> <key>realtime_scheduling</key> <value></value> </param> <param> <key>_coordinate</key> <value>(10, 10)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> </block> <block> <key>variable</key> <param> <key>id</key> <value>samp_rate</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>value</key> <value>32000</value> </param> <param> <key>_coordinate</key> <value>(10, 170)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> </block> <block> <key>blocks_throttle</key> <param> <key>id</key> <value>blocks_throttle_0</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>samples_per_second</key> <value>samp_rate</value> </param> <param> <key>vlen</key> <value>1</value> </param> <param> <key>_coordinate</key> <value>(481, 479)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> </block> <block> <key>analog_sig_source_x</key> <param> <key>id</key> <value>analog_sig_source_x_0</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>samp_rate</key> <value>samp_rate</value> </param> <param> <key>waveform</key> <value>analog.GR_COS_WAVE</value> </param> <param> <key>freq</key> <value>5000</value> </param> <param> <key>amp</key> <value>1</value> </param> <param> <key>offset</key> <value>0</value> </param> <param> <key>_coordinate</key> <value>(247, 450)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> </block> <block> <key>qtgui_sink_x</key> <param> <key>id</key> <value>qtgui_sink_x_0</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>name</key> <value>QT GUI Plot</value> </param> <param> <key>fftsize</key> <value>1024</value> </param> <param> <key>wintype</key> <value>firdes.WIN_BLACKMAN_hARRIS</value> </param> <param> <key>fc</key> <value>10000</value> </param> <param> <key>bw</key> <value>samp_rate</value> </param> <param> <key>rate</key> <value>10</value> </param> <param> <key>plotfreq</key> <value>True</value> </param> <param> <key>plotwaterfall</key> <value>True</value> </param> <param> <key>plottime</key> <value>True</value> </param> <param> <key>plotconst</key> <value>True</value> </param> <param> <key>gui_hint</key> <value></value> </param> <param> <key>freqchangevar</key> <value>None</value> </param> <param> <key>_coordinate</key> <value>(757, 446)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> </block> <connection> <source_block_id>analog_sig_source_x_0</source_block_id> <sink_block_id>blocks_throttle_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_throttle_0</source_block_id> <sink_block_id>qtgui_sink_x_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> </flow_graph> _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio