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Sweep tab
The gain slider automatically combines the LNA and VGA sliders. The LNA and VGA sliders directly control the parameters of the HackRF's input circuits. The optimal setting is LNA 40 dB and VGA < 18 dB. If the signals at the input should have a higher level, reduce the overall gain. If the signal is still weak with this setting, turn on the internal RF pre-amp, or use an external preamplifier. Warning: the overall signal strength at the HackRF's input must not exceed +10 dBm, in case of activated internal RF pre-amp max -5 dBm!
This checkbox controls the internal HackRF's RF pre-amp. Use in case of analysis of very weak signals (internal RF pre-amp should add extra approx. 14 dB of gain). Warning: the total signal strength at the HackRF's input must not exceed +10 dBm, in case of activated internal RF pre-amp max -5 dBm!
This checkbox turns on antenna power. 3.3V DC will appear on the antenna connector.
Use this checkbox to get rid of spur artifacts in spectrum chart and waterfall. They are usually displayed as amplitudes (infinite vertical lines on waterfall) that do not change over time and do not actually exist in the signal. They do not disappear even after disconnecting the signal or antenna. Usually their position changes with different frequency range settings. They can be various remnants of harmonic signals of the HackRF's internal clock.
Spur artifact filtering takes a fraction of a second to load a representative evaluation sample. If artifacts appear even with the checkbox checked, uncheck it and check it again. This is usually necessary after switching frequency ranges.
These checkboxes enable and disable individual types of traces on the spectrum chart. Enabling some traces also activates other possible settings on the Parameters tab that are related to them. You can choose 5 different traces:
- REALTIME - white
- PEAK - green
- AVERAGE - yellow
- MAX HOLD - red
- MIN HOLD - blue
The REALTIME trace shows instantaneous samples that were captured by HackRF and since it is a very fast, constantly repeating process even hundreds of times per second, it can be very difficult to read in the case of very short pulses. Therefore, other traces are also available, such as:
The PEAK trace shows instantaneous samples, to which a holding algorithm is applied, which you can set according to your own requirements. The PEAK trace can gradually decrease if the same or higher value is not repeated immediately after the peak (maximum) is captured. It is therefore ideal for monitoring the course over time, which everyone can adapt to their own needs. The PEAK trace is the source of statistical calculations, the results of which are in the lower right corner of the Waterfall. By turning off the PEAK trace, this data will no longer be displayed. At the same time, some PEAK trace data is recorded if STATS logging is turned on. Therefore, after turning off the PEAK trace, it is not possible to log STATS.
The AVERAGE trace shows data that is the average of several PEAK traces. The number of iterations can be set in the Params tab. At the same time, the AVERAGE trace can be "moved" along the Y-axis, as in some cases it can undesirably hide below the -100 dBm limit.
The MAX HOLD trace shows the maximum values that the PEAK trace has reached, but these are remembered on the screen.
The MIN HOLD trace shows the minimum values that the PEAK trace has reached, but these are remembered on the screen. MIN HOLD trace is enabled only by checking MAX HOLD MARKER checkbox.
All traces can be displayed simultaneously.
A special case of display is PERSISTENT, which expresses the representation of certain frequencies over time. Individual times of representation are color-coded. The longer a signal is present at a certain frequency, the "redder" the coloration. Sporadic signals are dark blue to black.
Markers turns on/off display of a small arrows on the spectral chart at the point where the maximum amplitude of the entire displayed frequency range is currently located. The amplitude and frequency values are also noted above the arrow. You can set up to 5 markers for the green PEAK trace and the red MAX HOLD trace. The Markers checkbox is only displayed if the corresponding trace is displayed.
Note: Checking MAX HOLD MARKERS checkbox changes adds blue MIN HOLD trace to the spectrum chart and calculates Mininum and Maximum total channel power on the waterfall's Information panel
RBW is the basic parameter for the resolution of the spectral chart display. It represents the smallest unit of resolution of one sample (FFT bin) on the graph. For example, for a frequency range of 40 MHz and an RBW of 50 kHz, one point on the graph represents a bandwidth of 50 kHz, and there are 800 of these points (FFT bins) on the graph in total (0.05 MHz x 800 = 40 MHz).
The smaller the RBW you set, the more detailed the graph will be. 3 kHz RBW is suitable for displaying small frequency ranges. However, this resolution can be very unclear for larger frequency ranges, so choose a larger RBW. The RBW setting does not affect the scan speed, but it does affect the total number of points on the graph, so that memory usage and size of recordings will be greater.
If you use the mouse to zoom in/out on the graph, the RBW will be automatically reset to the optimal value. In this case, set the required RBW value manually.
If you use Frequency presets, it is necessary to enter the desired RBW value for each defined frequency range in the Presets.csv file, to which the spectrum analyzer should be set after starting the scan.
The frequency shift parameter is used in connection with the use of an up-/down-converter at the HackRF's input. For ranges around 0-30 MHz, an up-converter is usually needed (e.g. SpyVerter has a shift of 120 MHz, for example, so we need to shift the frequency axis back by -120 MHz). Satellite TV LNBs are down-converters that shift signals with frequencies of 10.7-12.7 GHz to 950-2100 MHz. Here, a positive shift must be set so that the X-axis shows the correct signal frequency.
If you use Frequency presets, it is necessary to enter the desired Shift value for each defined frequency range in the Presets.csv file, to which the spectrum analyzer should be set after starting the scan. Use 0, if no shift is present.
The Amplitude offset slider shifts the Y axis of the graph of all traces down or up by the selected number of dB. It is used especially if you want to use the entire spectrum dynamics for different frequencies in a comparable way. For example, HackRF has different sensitivity at different frequencies, so certain ranges may appear higher or lower on the Y axis, comparable to the others. The RBW setting also affects the amplitude. This slider will help correct this situation.
If you use Frequency presets, it is necessary to enter the desired Amplitude offset value for each defined frequency range in the Presets.csv file, to which the spectrum analyzer should be set after starting the scan. Use 0, if no offset is present.
The Power calibration slider is used to correct the display of the total channel power in µW/m², displayed on the information panel in the right of the waterfall and also included in the STATS logs. The individual powers in dBm are summed for each FFT interval. The power flux density is calculated from the summed power, which allows an approximate calculation of the RF field strength.
Use the Power Calibration slider to set the power flux density value to match the current calibration value of a known source or calibrated measuring instrument. Any further sweeps will then display approximately acceptable power flux density value.
Note: however, with each change of frequency range or antenna change, the current calibration will probably be invalid and will need to be set again.
When an I/Q WAV, raw PCM, or CU8 file is opened with the REPLAY button, the Sweep tab also shows additional controls for replayed I/Q data. These controls are hidden during normal live spectrum sweep.
The Audio checkbox enables audio demodulation from the replayed I/Q signal. The slider next to it controls audio volume, and the AM/FM selector chooses the demodulation mode.
Audio demodulation gets data from full replayed spectrum, or from specific frequency range selected. Therefore if you need to check audio from part of current spectrum, simply zoom-in.
The Burst det checkbox enables burst detection during I/Q replay analysis. Burst activity can then be used for quick visual inspection of pulsed or packet-like signals.
The TX checkbox enables transmission of currently replayed signal through the connected HackRF. The TX power slider sets the output gain from 0 to 47. The RF pre-amp checkbox can also increase transmission output level of about +14 dBm, when enabled.
The TX frequency field contains the transmission center frequency in MHz. By default it follows the center frequency detected from the replay file name or file header. Check Custom freq if you want to set a different transmission frequency.
Together with the I/Q recording function in the time-domain analyzer window, I/Q replay with TX enabled can be used as RF signal recorder/player.
Warning: TX replay transmits signal through HackRF. Use it carefully, only with suitable attenuation/load. Make sure you comply with local regulations.