Perseus calibration
If you want to measure offsets (slight deviations from AM carrier frequencies) a receiver calibration is required. Unfortunately there are limitations to this in the Perseus software. Calibration using the Cal-button is only possible by full Hz values.
The easiest way get some more precision is to tune to a higher frequency and calibrate there accordingly. But also peak frequencies only shown in full Hz. If you want to become more precise you need some workarounds.
Using Spectrum Lab software for offset measurung
Spectrum Lab is great for spectrums and waterfalls. It even has offers direct Perseus integration. However, the GUI is not so intitive for listening purposes. Wouldn't it be nicer to use the Perseus GUI while analyzing the spectrum? A convenient help is Virtual Audio Cable (VAC).
- With VAC tune to the reference frequency (in this example 3330 KHz) in DRM mode. Or alternatively, use USB and tune to a frequency 8 Khz below the carrier (other values possible, also works with KiwiSDR and other remote receivers) with 25 KHz filter full open, calibration off
- In Spectrum Lab select VAC as audio input, your sound card as output, sample rate 192000, highest FFT 2M, center spectrum on 8000 KHz, string expression for configurable button on the left:
"peak at "+str("###0.000 Hz",peak_f(7900,8100))
- Now you can read the calibration demand from the SpecLab button. Example: 8009.121 Hz. You have deviation of 9.121 Hz on 3330 KHz.
- Calculate the deviation for 39000 KHz: 9.121 Hz /3330*39000=106.81 Hz
- Tune Perseus to 39000.107 Khz and click "Cal"
- Now you can do the demodulation part in Spectrum lab: Go to the Options/Audio menu and click on I/Q audio adjustment (bottom left)
- Click on the the DSP blackbox marked with ? right of L4 and select AM demodulator with options: center frequency 8000 Hz
- In the output D/A converter below L6 select Enabled
- Now you can live track the strongest peak while tuning to any frequency and listen to the audio. The bandpass can be configured with the Perseus GUI
Recorded files
Unfortunately it is not possible to calibrate the recordings within the Perseus software. So you need to calculate. If you know the receiver's offsety of
at least two frequencies you can calculate the rest. This little script makes it easier. I've already calibrated some of the public files, or you
can use the form.
Calibration tables for of public files
- Australia, Green Cape, 3-Nov-2008 1800 UTC
- Canada, Masset, BC Jan-2009 1700 UTC
- Canada, Pontneuf, QC, 2-Feb-2009 2200 UTC
- Finland, Joensuu 28-Jul-2009 2000 UTC
- Finland, Joensuu 24-Jul-2009? 1900 UTC
- Finland, Joensuu 16-Dec-2008 1300 UTC
- Japan, Chigasaki 12-Jan-2009 2100 UTC
- Germany, Handewitt 17-Feb-2009 03 UTC
- Germany, Freising, 22-Sep-2009 1732UTC
- Greece, Athens 25-Jul-2009 1900 UTC
- Greece, Athens 28-Jul-2009 2000 UTC
- Greece, Athens Jul-2009 2100 UTC (150-950 KHz)
- Greece, Athens Jul-2009 2200 UTC (900-1700 KHz)
- Norway/Svalbard, Kongsfjord 01-Nov-2008 1300 UTC
- Norway/Svalbard, Kongsfjord 10-Jan-2009 1430 UTC
- Norway/Svalbard, Kongsfjord 09-Jan-2009 1900 UTC
- Norway/Svalbard, Kongsfjord 26-Feb-2009 0600 UTC
- South Africa, Seefonstein, 31-03-2010 0400 UTC
- South Africa, Seefonstein, 31-03-2010 0500 UTC
- South Africa, Seefonstein, 29-03-2010 1900 UTC
- UK Nottingham (Faulkner) 3-Feb-2009 1400 UTC
- UK Scotland Ayrshire (Baird), 23-Jan-2009 2300 UTC
- USA, Central PA 03-Jan-2009 2200 UTC
the WAV files are available at
Individual calculation