VA3ROM SuperSID recordings of NPM (Hawai'i VLF US Navy Transmitter)

[va3...@gmail.com]

My GPSDO lock Flex-1500 and Fldigi Frequency Analysis monitoring WWV on 10 MHz was off air because of I/O (idiot operator) error (it's an old FORTRAN programming pun) I call it a "grape 2" HamSCI receiver since it's a bit more versatile than the grape 1 receiver. Would be nice to be able to stream Fldigi data to a central web server in real time I do with PSKReporter, SID.Stanford, and WSPRnet et al.  And I digress...

But, fortunately, my SuperSID VLF station was on air and after reading some group postings, I had a look at the received NPM Hawai'i VLiF US Navy transmitter signals given its proximity to the Tongo Pacific sea floor volcano eruption. I'm no expert in interpreting the plots, but i f I had been thinking more I/O error, I would have immediately accessed the online sid.standford.edu/database-browser respository of the many SuperSID feeds but they only go back in time 3 days and I suppose the webmaster is the only person who can get older data for you.

My SuperSID receiver was off air for 14 January because the feed line entering the house was under the gas furnace vent and now encased in layers of rime ice. Ice is a living thing and had ripped open the RG6 sheathing and mangled the inside so I had to do a splice repair in -30C bare handed. Thank goodness for compression F connectors and the proper tools to prep the coax and compression crimp connectors! But I lost a lot of SuperSID data until I realized what was wrong and fixed the problem.

I've included the plotted graphics from my local SuperSID CSV NPM data for 13, 15 and 16th January. Other SuperSID users who also archive their data locally would be able to do the same with their NPM or other VLF beacon data. I'm no expert but it seems to me that the NPM graphic for the morning of 15 Jan indicates anomalous activity but hindsight is 20-20 since I know what happened. But if I didn't know it, would I draw the same conclusion without a lot of data from all sources around the world and being blind to what I was looking for to avoid confirmation bias.

Anyway, if anyone wants the raw SuperSID NPM CSV data or the data for NLK and NAA for the 13, 15 and 16 let me know and I'll send them via the group.

73,

Robert, VA3ROM

[Jonathan]

Hi Robert,

This is excellent data! I built a VLF receiver and use a Raspberry Pi
with Audio Injector soundcard to capture the VLF spectrum up to 48
kHz. I wasn't monitoring NPM, unfortunately, but I think I will now. I
have plots of NAA, NAU, and NLK for those three days. I use
vlfrx-tools to capture and record amplitude and phase of the carrier.
Unfortunately for those three days, due to a Trimble firmware issue
that they refuse to fix currently, I don't have phase data because of
a GPS receiver issue.

I have attached my plots of NAA and NAU for those three days. NLK
didn't seem to indicate anything significant from my VLF receiver's
QTH but I attached the plot anyway. You can definitely see a dip in
NAA's amplitude on the 15th at 5-6UT. You can see a dip with NAU too,
but I'm not sure if that is significant, but comparing the day before
and after, it might be. Do you also have plots from NAA and NLK?

Your plots of NPM may show ionospheric perturbation, but even with my
NAA plots, it also could be typical diurnal activity of the ionosphere
at VLF. With VLF transmitters and SIDs, including the Tonga event,
propagation path from the transmitter to your VLF receiver's QTH plays
a very important role in whether you will see a SID in your data.

One paper applicable to this (gravity waves affecting VLF propagation)
can be found here:
https://angeo.copernicus.org/articles/38/385/2020/angeo-38-385-2020.pdf

I had another paper about how the propagation path affects SID
detection but for the life of me, I cannot find it right now. I'll
post it when I do.

Thanks.

Jonathan
KC3EEY

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[David Themens]

Hi,

That's very nice data. It lines up quite well with the anticipated diurnal variation of the lower D-Region (particularly those spikes in the morning and evening). Here's modeled D-region electron density at 65km altitude for reference (I wasn't sure where your receivers and the transmitters are so I just used Millstone for illustration):

Cheers,

David

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[Jonathan]

Hi David,

My receiver is located in Springbrook Township, PA. Can one use the output
of this model to estimate signal strength?

Jonathan
KC3EEY

On Sun, 23 Jan 2022, David Themens wrote:

> Date: Sun, 23 Jan 2022 08:38:39 +0000
> From: David Themens <david....@gmail.com>
> Reply-To: ham...@googlegroups.com
> To: ham...@googlegroups.com
> Subject: Re: [HamSCI] VA3ROM SuperSID recordings of NPM (Hawai'i VLF US Navy
> Transmitter)

>> https://groups.google.com/d/msgid/hamsci/CAOY0kB1L4qmG3P8ZVaQMzJMQju9oYzNT83Xu_b66SnpvA0OGJw%40mail.gmail.com
>> .

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[David Themens]

Hi,

It should be possible, with a couple of assumptions, but you would need a good VLF propagation model, which may be the limiting factor. 

Cheers,

David

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