which parameters i have to set for my desired frequency range?
Dear devs,
i want to scan the frequency range from 88 MHz to 108 MHz.
The first thing i was asking me is which string i should use to connect to the spectran ? (spectranv6/sweepsa or spectranv6/raw)
And what is the difference between them?
Next thing i noticed, depending on which connection string i use from above i can set a different set of parameters to the device (some parameters are only accepted wich specific connection string).
Here are the parameters i've set (lines which starts with # are just comments):
# Zeichenfolge für Verbindung
ConnectionString=spectranv6/raw# Datenkanal zuweisen (Rx1 spectra output=2)
datachannel=2# Ausgabe der Sampledaten
device/outputformat=spectra# Bandbreite
#main/rbwfreq=500000# Empfänger-Kanal
device/receiverchannel=Rx1
#device/receiverchannelsel=Rx1# Referenzlevel
main/reflevel=-38# Parameter für Spektrumanalyse
#main/startfreq=88000000
#main/stopfreq=108000000
#main/centerfreq=2400000000
#main/spanfreq=20000000
main/centerfreq=98000000# Sampledaten-Aufbereitung
#device/fft0/fftmergemode=avgmain/decimation=1 / 2
device/usbcompression=raw
calibration/preamp=Amp
Now to the proof that some of the config are not correct.
If i received a data packet from the spectranV6, the start frequency are somewhere in nowhere:
cbsize=112 (size of data structure, filled in by caller)
streamID=201
flags=65541
startTime=1680245729,66114 (start time in seconds since start of the unix epoch)
endTime=1680245729,66186 (end time in seconds since start of the unix epoch)
startFrequency=173330000 (start frequency of the data)
stepFrequency=45000 (bin size or sampel rate of the data)
spanFrequency=38340000 (valid frequency range, center is start + span / 2)
num=64 (number of samples used in the packet)
total=0 (total number of samples of the packet)
size=852 (size of each sample)
stride=852 (offset from sample to sample in floats)
fp32=1700258385152 (actual sample data)
rbwFrequency=61798,5 (realtime bandwidth in spectrum data)
What should i have to configure to make it work correctly?
Thanks.
The difference between "raw" and "sweepsa" is that the former is the realtime measurement (this is what the V6 block does in the RTSA-Suite), which only allows limited configuration of frequency parameters. Mainly centerfrequency, receiver bandwidth and span factor (decimation). So you can't configure an exact frequency range in that mode, but have to filter the resulting samples manually. Also there are some restrictions regarding the frequency range, in particular the minimum frequency you can configure. The flipside of that is that you get the highest measurement speed.
"sweepsa" on the other hand allows adjusting frequency parameters precisely, and also enables to measure a much higher frequency range without having to mess with reconfigure parameters constantly. It basically implements the functionality of the Spectran V6Sweep Zoom block of the RTSA-Suite. Downside is that this causes some overhead which can impact measurement speed negatively, and you no longer have direct control over some settings.
The problem you have comes from using "raw" mode: The specific combination of center frequency, span factor and receiver bandwidth would result in a frequency range not covered by the automatic filter selection, so the centerfrequency is adjusted upwards (you can test this with the RTSA), which results in a much higher start frequency than expected. Span frequency is a result of span factor (decimation) and receiver bandwidth, it cannot be configured directly in "raw" mode. Same goes for rbwfrequency.
So for your case you probably want to use "sweepsa" instead of "raw" and configure start- and stop-frequency directly (see the SweepSpectrum example in the sdk directory).
