SID detection with SpectrumLab

[HN50]

Well,

The run for 135-315 has been running for just over 4 days, so I thought I would load the data into my database and see what things look like...

MinLogDateTime         MaxLogDateTime       DaysRun  Notes
2017-06-05 06:02:00  2017-06-10 14:05:00  5.3          00-180 orientation
2017-06-10 15:44:00  2017-06-14 18:36:00  4.1         135-315 orientation
2017-05-27 04:34:00  2017-06-05 05:56:00  9.0         45-225 orientation
2017-05-19 19:44:00  2017-05-27 04:33:00  7.4         70-250 orientation
2017-05-14 11:26:00  2017-05-19 19:35:00  5.3         90-270 orientation

As expected everything bar RDL (18.1kHz) and HWU (18.3kHz) is too weak to show anything - there may be hints of differences between day and night but not a great deal.  My only reservation is that 45-225 ran for nearly double the length of time as some of the others, but I think I just have to accept this at the moment.

RDL

Having looked at this I think that probably the strongest signal is the 70-250  Even when averaging none are particularly smooth, but at least this would agree with the idea that the antenna should align with the direction that the transmitter is (approximately 70 degrees).  So although not an Earth-shattering observation it at least seems to agree with what I was expecting. 

Feel free to disagree.

HWU

Hmm, well, I think Rosnay is close to a bearing of 135 from where I am.  However 70-250 and 45-225 are not that much behind.  I think though looking at the results; and putting the issue of noise to one side; I don't think I need to worry too much about building an antenna with two loops (although I like the idea!) as 70-250 might just give a reasonable strength for both RDL and HWU (18.3).

So I am off to reorient the antenna back to 70-250.  I am going to reduce the logging rate down to once per minute, my hope being that doubling the sample time might help smooth the results a little.  Let's see.

Cheers,

Dave

 

[robinst]

Hello, nice work with the rig and posting all the data, really interesting to read and got myself to try to set up a system too. 

Regarding the filter, the resistor should be connected to the other lead from the antenna and not your house electrical ground. The filter needs to work against the signals "ground" or reference to be effective, in this case, the other lead from the antenna. The filter circuit is basically a voltage divider with the capacitor as a frequency dependent resistor. A 10 kHz signal will see the 100 nF as 160 ohm, 1 kHz will see it as 1600 ohm and 100 kHz sees it as 16 ohm. Basically the current from the loop antenna has to pass trough your capacitor and resistor and then back to the antenna, and depending on the frequency you will see that more or less of the voltage will be seen over the resistor or the capacitor. At 10.6 kHz equal amount of voltage will be seen over the resistor and the capacitor. 

The resistor might dampen the total signal thou, as the antenna is a quite weak current source, but if that becomes a problem you can try to scale the filter to use maybe 15 kohm instead, as it will "load" your loop antenna less.   

[Dave Simons]

My super sid has just arrived, I'll be learning significantly from you blokes so thanks in advance.

[HN50]

On ‎19‎/‎06‎/‎2017 at 16:32, robinst said:

Hello, nice work with the rig and posting all the data, really interesting to read and got myself to try to set up a system too. 

Regarding the filter, the resistor should be connected to the other lead from the antenna and not your house electrical ground. The filter needs to work against the signals "ground" or reference to be effective, in this case, the other lead from the antenna. The filter circuit is basically a voltage divider with the capacitor as a frequency dependent resistor. A 10 kHz signal will see the 100 nF as 160 ohm, 1 kHz will see it as 1600 ohm and 100 kHz sees it as 16 ohm. Basically the current from the loop antenna has to pass trough your capacitor and resistor and then back to the antenna, and depending on the frequency you will see that more or less of the voltage will be seen over the resistor or the capacitor. At 10.6 kHz equal amount of voltage will be seen over the resistor and the capacitor. 

The resistor might dampen the total signal thou, as the antenna is a quite weak current source, but if that becomes a problem you can try to scale the filter to use maybe 15 kohm instead, as it will "load" your loop antenna less.   

Hi robinst,

Apologies for not getting back to you sooner, work and other things have been getting a bit in the way.  Thank you for the posting.

Looking over your comment, are you saying that the filter should look like the following instead?  Given that it is just a loop antenna with no amplifier, do you think it is worth adding the high pass filter at all? 

Thanks,

David

[HN50]

It has been a little while since my last post. 

For some reason the SQL Server Integration Services package that I built to pull the data out the script file and load it into the database got corrupted, so I had to spend time working out why it was misbehaving.  I also read that the average temperature on Venus is about 460 Celsius, which is only a couple of degrees warmer than my loft in the recent hot weather we have been having.  And hence I had no great desire to go up there for longer than a few seconds at a time.

However, in braving the heat I have been able to do some 'system testing' by way of trying to work out what is causing all the noise in my plot.  The heat made my laptop go funny, so I had to turn it off, and on switching back on I could not quite remember which settings file I used, so I picked the one I though I had been using but was presented with the following.

 

Which looks at significant variance to what I had been seeing before, in that now I can actually see the VLF station plots(!).  I am sure that reading the manual would have told me sooner, but this is all a bit trial and error anyway.  I was also pleased with the rather noise free appearance of the plot - all good so far. 

However as the battery is old and with a capacity not a whole lot larger than a watch battery I had to nip down the ladder to turn the mains extension on.  Which did the following.

Blast. 

I can still see the stronger signals, but all that other noisy rubbish can't be helping.

Now, I am not so proud to not be able to admit I am wrong, but I had been adamant that it was the phone lines outside despite wiser council saying it could be the mains electricity.  But it would appear that the main source of interference is the very thing that is powering my laptop. 

So, I am deciding between;

1) Get long aux cable to connect loop antenna and move aerial somewhere else in my roof. 

2) Have laptop down in wardrobe and long aux cable up into roof

3) Have long DC extension from mains adaptor up into the roof.

Having the laptop down in the wardrobe would make getting data out easier, however it isn't big and I do actually need the space for clothes.  So I am leaning between 1 or 3.  I like the idea of trying to find an additional DC extension cable, as otherwise the location for the aerial seems to reasonable. 

Anyway, I am loading my data now and will have to see what comes out the analysis. 

Dave

 

[HN50]

10 hours ago, Dave Simons said:

My super sid has just arrived, I'll be learning significantly from you blokes so thanks in advance.

Hi Dave,

Thanks for the post, look forward to seeing the SuperSID running.  That is an actual receiver in its own right, isn't it?

Dave

[HN50]

My only conclusion from tonight's data analysis;

I need to buy better data analysis software.

I am all for open source software, but LibreOffice is really struggling with 110k rows...

[HN50]

Well, it has taken me about 3 hours to tease a graph out of LibreOffice and it is not very readable at the moment.  However I will be pleased with what I have managed to get so far, it runs from 02/07/2017 00:00 to 09/07/2017 00:00.  I can see the difference between the day and night signal as compared to other plots posted, though the signal is still very noisy.  But it looks better than earlier ones.  I will work out which SID setting file I used for SpectrumLab and post the name.

Tomorrow I might even try and create another graph. 

Dave

[HN50]

It has been a few days since my last post butI have managed to pull out some more graphs from LibreOffice for week 27 for some of the other transmitters I am monitoring and got them into graphs.

They are all starting to show the diurnal variations I was hoping to see, however even with a 10 minute moving average they are still quite/very noisy; on balance I think the Skelton plot is the best.  I think though that a flare would have to be an X class beast though for me to spot it(!!).

Anyway, I have been giving thought to see if I could reduce the noise from the mains cable/laptop transformer by moving the position of the antenna to the cable and laptop, as well as using silver foil to try and shield wires  :).  Alas I have found that pretty much wherever the antenna is in my roof, once the mains is delivering power the noise is quite bad (the horizontal line at 13:26 and the signals that change frequency with time are the neighbour firing up his electric lawnmower).  So I decided to bring it down into my wardrobe, with a 10m aux cable coming down from the antenna.  If I am getting noise everywhere, I might as well have the laptop somewhere I can get to it a little easier.

The main improvement for me in noise reduction is to have the laptop running off its battery, so I have been looking at how long the battery actually lasts, versus how long it takes to charge.  I have set low power mode and set the screen to fully turn off after 1 minute and at the moment I am estimating that it will run for 4 hours and 10 minutes on one charge.  I think there are a few other things that can be done to try and eke out a few extra minutes.  

I will then look at how long it takes to full charge the battery, as one option is to get a timer that kicks in after 4 hours.  That does mean that at some times of the day the noise levels will increase when it is charging, but at the moment I think that is just something I will have to accept.

Alternatively I put the laptop back in the roof, but look for a dc extension that I can run back up to it; perhaps having the transformer a few meters from the laptop might help.

But let's see how the discharge and recharge tests go...

 

[HN50]

Oh yes, the configuration file I am using is called 'VLF_Stations.usr'

[Dave Simons]

On 7/11/2017 at 06:33, HN50 said:

Hi Dave,

Thanks for the post, look forward to seeing the SuperSID running.  That is an actual receiver in its own right, isn't it?

Dave

Yes in my case its the receiver, (I actually got 3, 2 for school and one for myself), now I need to build the antenna, after completing my radio jove reciever. (So many oportunities and so little time).

[robinst]

That filter looks corect bur regarding if it will help I don't know, it depends on what kind of noice you need to get rid of. A low pass filter (switching positions of the capacitor and resistor) might help better with getting rid of high frequency switch noice from the laptop charger. A FFT is usually good at extracting signals from noice as long as the noice is not saturating anything, like the ADC. 

Another way to tackle the EMI noise from the charger. You can try to add some (or lots) of clip on ferrite filters on all cables to and from the charger. https://en.wikipedia.org/wiki/Ferrite_bead That might help a little bit if the noice you see is a high frequency aliased down to a lower frequency instead of an actual low frequency signal. Another thing that might be good to clarify is if the noice is radiated and then picked up by the antenna or if it is coupled to the sound card trough the cable from the charger. How does a spectrum look with the charger connected and the antenna disconnected? 

A fourth alternative is to use a USB extension and put the sound card directly at the antenna, this might reduce the risk of the analogue cable picking up noice.

 

Regarding the data analysis, maybe looking at writing like a python script to automate it instead of using a spreadsheet? Using a package like pandas might be a good start?

[HN50]

It has been nearly a year since I updated this (!!!) but I have had a hankering to get back to it.  I had some time off recently so decided I would build a bigger aerial, using the method in the S@N article.  I had some pine beam kicking about and I bought a spool of doorbell wire.  The hatch into my loft at its widest is just over 1m, so I figured an aerial with 1m sides was the biggest I could build.   After several hours of working I was left with this;

Not pretty, but it looks like  a loop antenna to me.  I had slightly forgotten how to use SpectrumLab, but once I had got it working again I was confronted with the following plot;

SpectrumLab seems to have decided to use different settings, but I don't remember seeing the transmitters like they appear with the 45cm sided aerial.  It is still noisy, but I can definitely see two, maybe 4 transmissions.  I even dared to believe that it looked a little like some of the other screenshots I had seen online.

I reset the plotter settings (below) and left it to run for 24 hours.

When I came back, I had the following;

A few of the signals are below the strength of the background noise (so I assume might as well be ignored), and most of the stronger signals are quite noisy, however I saw that 22.1k is looking rather smooth.  So I might have one signal that is usable.

I am currently writing a powershell script that will pivot the data into rows rather than columns to make analysis easier in a spreadsheet; SpectrumLab is determined to log max, min and average; and I will also have to think about aligning the antenna to see if that will improve some of the other signals (I plonked it down just to get going), but at the moment the increase in antenna size does seem to have been helpful.

So I will keep logging and see how things progress.

 

[davy999]

Looks good, if ever you want to check against another system I have been running an SID detector at home for many years.

Mine, and a friend's live SID detector plots are shown on my website here.

http://www.merriott-astro.co.uk/vlf.htm

 

I just use a long loop hung on the side of the house and fence and I get some cracking SID detections.

 

Regards

Dave