Tagged: 1 month 1 week ago
Hello fellow members of the Flamsteed Radio Astronomy Group,
It was agreed at our last meeting that we would attempt to collect SID data from our varied VLF receiver systems tuned to the Ramsloh transmitter (23.4kHz) on the days of 27th, 29th June and the 1st July , starting at 00:00:00hrs UTC and ending at 23:59:59hrs UTC. For those of us using Spectrum Lab it would be desirable that data for each day exported from the Watch Window should be stored in a csv (comma separated variable) text file. Time should be saved in column 1 of the data set with the signal amplitude in column 2. How to achieve this is explained in the Spectrum Lab Manual, accessed by the following link:
The time zone should be UTC in the format YYMMDD hh:mm:ss .
If you have been unable to calibrate your system the signal amplitude should be expressed as dB (or dBfs) as explained in the Spectrum Lab Manual:
“For absolute measurements, the input amplitudes must be calibrated. Amplitude display units like Volts or dBuV only make sense if the relationship between A/D converter value and absolute input voltage is known. Otherwise, stick to the <u>default amplitude display unit</u> which is “dBfs” (dB relative to full scale) .”
If you are not using Spectrum Lab to analyse and record the VLF signal it would appreciated if the data could be recorded in the format described above as this will simplify the task of collating the data sets.
If/when you have successfully collected the data, (even if for just one of the chosen days), please email it to me and I will attempt collate our data sets.
Here’s hoping for an SID event on at least one of the days!
Further SID collections. Could you please answer a few questions for me, as I wish to try to start writing a Python program for my Raspberry Pi. I am using Anaconda version of Python 3.4 as it does a very good check on the mistakes I make, so Q1, what is the best version of a FFT, I have tried numpy and scipy but I realise that there are more versions out there and I remember you saying that you need a very fast version. Q2. What am I trying to achieve, is it that I need to carry out FFT on a frequency of one of the stations ie. Say DHO38 at 23.4k Hz centre frequency and so many samples either side, how many samples would you suggest, and what amplitude would I use. Q3. The signal that we are processing from the aerial is amplified then Analogue to Digital Converted? and then FFTed so that we are processing a digital signal?, or have I got that round the wrong way. I would appreciate your guidance on these points, as the nights are drawing in, and I need something to keep me going.
Another NMEA-0183 sentence that could be used is GLL. This is a very simple sentence.
GLL Geographic Position – Latitude/Longitude
The GLL sentence will contain the following data:
LatitudeN or S North or SouthLongitude
E or W East or WestTime UTCStatus A – Data Valid, V – Data InvalidChecksum
thanks schick and members confirm by the 5th so I can find out what the budget may be and I can get a potential product list up. If not confirmed by the 5th team will be open.
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