[TangerineSDR] [HamSCI] First Amateur VLF Transmission Detected at the W2NAF-KC3EEY VLF Receiver!

Jonathan emuman100 at gmail.com
Sun Jan 22 13:06:57 EST 2023 

There was one more thing I wanted to mention. Just like VLF transmitters,
amateur transmissions in the VLF band are also susceptible to propagation
anomalies from solar flares and GRBs.

Here is a plot from Markus showing amplitude and relative phase of DL3JMM’s
transmissions from Markus’s VLF receivers in Germany. Markus has a triple
axis system (N-S/E-W B-field and E-field). Markus’s plot shows a SID in
DL3JMM’s transmission caused by an M-class flare:
[image: image.png]
How cool is that?! Credit to Markus for creating the plot.

Even cooler is that the SID was also detectable on NAA, NAU, and NLK on the
Springbrook VLF receiver!! Here are the amplitude plots for NAA and NAU
showing the M-class flare:
[image: Screen Shot 2023-01-22 at 12.47.16 PM.png]

[image: Screen Shot 2023-01-22 at 12.48.15 PM.png]
What an amazing first this was! Not only was the transmission detected
(both the carrier integration and EbNaut decoded), but an M-class solar
flare caused a SID that was observed both on DL3JMM's signal at a VLF
receiver in Germany, it was also observed on NAA and NAU locally! I'm very
happy with this!

Jonathan
KC3EEY



On Sun, Jan 22, 2023 at 1:17 AM Jonathan <emuman100 at gmail.com> wrote:

> There was one more thing I wanted to mention. Just like VLF transmitters,
> amateur transmissions in the VLF band are also susceptible to propagation
> anomalies from solar flares and GRBs.
>
> Here is a plot from Markus showing amplitude and relative phase of
> DL3JMM’s transmissions from Markus’s VLF receivers in Germany. Markus has a
> triple axis system (N-S/E-W B-field and E-field). Markus’s plot shows a SID
> in DL3JMM’s transmission caused by an M-class flare:
>
> How cool is that?! Credit to Markus for creating the plot.
>
> Jonathan
> KC3EEY
>
>
> On Sun, Jan 22, 2023 at 1:02 AM Jonathan <emuman100 at gmail.com> wrote:
>
>> Thank you everybody! This is quite an exiting first for the VLF system
>> and represents the amazing opportunities for radio amateurs in the VLF
>> band!
>>
>> It's interesting that there was only 10.6dB more attenuation in the
>> east-to-west direction, but the nice thing about VLF and ULF is that the
>> path losses are low, contributing to the usability of the band. Perhaps the
>> earth's magnetic field in that direction had some influence on the path
>> loss, similar to the instances I've read about with VLF transmitters and
>> even ELF components of sferics.
>>
>> I wanted to see if I could get more decodes from stacking the other
>> transmissions. I tried stacking transmissions of the same time on both
>> 14th, 15th, and 16th and I also tried stacking the transmissions of the
>> 15th and 16th.
>>
>> I was only able to get an additional decode by stacking the 00:00 and
>> 06:00 transmissions on the 16th. Here are the results:
>>
>> initial reference phase -31.8 amplitude 3.601e+01
>> phase   0    0    0    0    0
>> found rank 0 ber 3.6133e-01 Eb/N0 0.5 M -7.734199219e+02 ph 0 0,0,0,0
>> [BERND]
>> carrier phase: 4.7 deg
>> carrier amplitude: 5.052e-02
>> carrier Eb/N0: 1.4 dB
>> carrier Es/N0: -11.18 dB
>> carrier S/N: 15.92 dB in 65.1 uHz, -25.95 dB in 1Hz, -59.93 dB in 2.5kHz
>>
>> I did not get a peak for the 16th's 00:00 transmission when I ran it
>> through vtnspec.
>>
>> Overall, I think this was a very successful transmission. Again, a big
>> thanks and congratulations to Paul, Bernd, and Markus! This was so much fun!
>>
>> Jonathan
>> KC3EEY
>>
>> On Wed, Jan 18, 2023 at 10:26 PM Julius Madey <hillfox601 at gmail.com>
>> wrote:
>>
>>> Congratulations Jonathan and Nathaniel ..!  Another first ?
>>> 73,
>>> Jules -K2KGJ
>>>
>>> On 1/18/2023 3:34 PM, Dr. Nathaniel A. Frissell Ph.D. wrote:
>>>
>>> That is wonderful news, Jonathan! Congratulations!
>>>
>>>
>>>
>>> 73 Nathaniel W2NAF
>>>
>>>
>>>
>>> *From:* hamsci at googlegroups.com <hamsci at googlegroups.com>
>>> <hamsci at googlegroups.com> *On Behalf Of *Jonathan
>>> *Sent:* Wednesday, January 18, 2023 12:57 PM
>>> *To:* TangerineSDR Listserv <tangerinesdr at lists.tapr.org>
>>> <tangerinesdr at lists.tapr.org>; Unknown <hamsci at googlegroups.com>
>>> <hamsci at googlegroups.com>
>>> *Subject:* [HamSCI] First Amateur VLF Transmission Detected at the
>>> W2NAF-KC3EEY VLF Receiver!
>>>
>>>
>>>
>>> A new first for the W2NAF-KC3EEY VLF receiver! Ameteur transmissions
>>> from VLF Radio Amateur DL3JMM in Germany have been detected at the receiver
>>> and messages have been decoded! DL3JMM's QTH is over 6500km away from
>>> Springbrook and consists of both a land and sea propagation path. The
>>> message was encoded using EbNaut, 8k19a polynomial coding, 16-bit crc, 5
>>> characters message length with a 30 second symbol period at a frequency of
>>> 8270.03Hz. This information is important to configure the decoder. The
>>> carrier's spectral peak can be seen on this spectrum plot integrated over
>>> the transmission period. It was generated on Paul's server from the
>>> uplinked vorbis encoded audio stream of VLF spectrum data.
>>>
>>>
>>>
>>> It also was detected at a VLF receiver at Forest, Virginia as well:
>>>
>>>
>>>
>>> I then pulled the spectrum data from the raw downsampled and hum
>>> filtered data and integrated over the length of the transmission. To do
>>> this, here is the vlfrx-tools signal processing chain. First, the spectrum
>>> is fed through a 3 kHz wide brick wall filter with a center frequency of
>>> 8270 kHz. Then, it's fed through a sferic blanker to blank out sferics
>>> based on a setting that produced the lowest noise floor. Finally, it's fed
>>> into the narroband spectrum analyzer with 53.07uHz resolution.
>>>
>>>
>>>
>>> vtfilter -h bp,f=8270,w=3000
>>> 2023-01-13_04-15-00_18900s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-18840s_high_power.vt
>>> | vtblank -a12 -d0 -t100 -v | vtnspec -v -r53.07e-6 -w0.01 -f8270.03 >
>>> "2023-01-13_04-15-00_18900s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-18840s_high_power.dat"
>>>
>>> It produced a narrowband spectrum with a carrier peak of 5.622e-08:
>>>
>>> vtnspec: amplitudes 0 m/p/r: 1.203e-08 5.622e-08 4.672 p-m 6.61 sigma
>>>
>>> The output data was plotted in gnuplot, also showing the carrier's peak:
>>>
>>>
>>>
>>> To see if I could get a decode, I ran it through the ebnaut decoder
>>> using the following vlfrx-tools processing chain. After the sferic blanker,
>>> the spectrum is fed into a multiplicative mixer at the carrier frequency to
>>> produce baseband IQ data. The output of the mixer is then downsampled and
>>> converted to ascii data, then sent to the ebnaut decoder with the encoding
>>> parameters of the message. -c2 tells the encoder to use both processor
>>> cores.
>>>
>>>
>>>
>>> vtfilter -h bp,f=8270.03,w=3000
>>> 2023-01-13_04-15-00_18900s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-18840s_high_power.vt
>>> | vtblank -a12 -d0 -t100 -v | vtmult -f 8270.03 | vtresample -r 240 |
>>> vtresample -r 1 | vtraw -oa | ebnaut -d -N5 -p 8K19A -S30 -k16 -r1 -c2 -v
>>> -L20000 -PS -T60
>>>
>>>
>>>
>>> But this did not result in a successful decode. A few more dB was
>>> needed. Thankfully, DL3JMM did more transmissions in his transmission
>>> campaign at the following times, he wrote:
>>>
>>>
>>>
>>> The next transmission already started at 18:00 UTC because 18 is modulo
>>> of 6h. So they begin
>>> next broadcasts probably:
>>>
>>> today (01.14):
>>>
>>> - 18:00
>>>
>>> tomorrow (01.15):
>>>
>>> - 00:00
>>> - 06:00
>>> - 12:00
>>> - 18:00
>>>
>>> Monday (01.16):
>>>
>>> - 00:00
>>> - 06:00
>>>
>>>
>>>
>>> Here is a spectrogram showing the transmissions. Between transmissions,
>>> only an unmodulated carrier.
>>>
>>> You can see the first transmission on the 13th, one on the 14th, four on
>>> the 15th, and the beginning of the one on the 16th.
>>>
>>>
>>>
>>> Paul was able to achieve a decode at Forest, VA for the midnight
>>> transmission on the 16th, however, I still needed a few more dBs for that
>>> transmission and recommended I stack both midnight transmissions. Stacking
>>> feeds both transmissions through an additive mixer and aligns timestamps
>>> and sampling. This allows the signal power from both transmissions to
>>> add and will increase the likelihood of a decode. First, I converted both
>>> midnight transmissions to baseband IQ data using the following vlfrx-tools
>>> signal processing chains:
>>>
>>>
>>>
>>> vtfilter -h bp,f=8270,w=3000
>>> 2023-01-14_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1.vt |
>>> vtblank -a12 -d0 -t200 -v | vtmult -f 8270.03 | vtresample -r 240 |
>>> vtresample -r 1 >
>>> 2023-01-14_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband.vt
>>>
>>> vtfilter -h bp,f=8270,w=3000
>>> 2023-01-15_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1.vt |
>>> vtblank -a12 -d0 -t200 -v | vtmult -f 8270.03 | vtresample -r 240 |
>>> vtresample -r 1 >
>>> 2023-01-15_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband.vt
>>>
>>>
>>>
>>> Then, I fed both into the stacking script:
>>>
>>>
>>> bash stack2
>>> 2023-01-14_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband.vt
>>> 2023-01-15_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband.vt
>>> >
>>> 2023-01-14-15_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband_stacked.vt
>>> 2023-01-14_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband.vt
>>> 1673740200.000000 3.914e+05 1.532e+11
>>> 2023-01-15_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband.vt
>>> 1673826600.000000 5.056e+05 2.556e+11
>>>
>>> Finally, I converted the stacked transmissions to ascii and fed it into
>>> the decoder. I GOT A SUCCESSFUL DECODE! The message is in brackets with an
>>> Eb/N0 of 2.5dB!!
>>>
>>>
>>>
>>> vtcat -S600
>>> 2023-01-14-15_23-50_16000s_DL3JMM_8270.03_8K19A-crc16-30s-5chars-16000s_1_r1_baseband_stacked.vt
>>> | vtraw -oa | ebnaut -dp8K19A -r1 -S30 -N5 -c2 -PU -L50000 -v
>>> initial reference phase -48.3 amplitude 2.244e+01
>>> phase   0    0    0    0    0
>>> found rank 0 ber 3.5156e-01 Eb/N0 1.2 M -8.639339600e+02 ph 0 0,0,0,0
>>> [BERND]
>>> carrier phase: -11.9 deg
>>> carrier amplitude: 5.749e-02
>>> carrier Eb/N0: 2.5 dB
>>> carrier Es/N0: -10.05 dB
>>> carrier S/N: 17.04 dB in 65.1 uHz, -24.83 dB in 1Hz, -58.81 dB in 2.5kHz
>>> elapsed 2
>>> phase   1  180  180  180  180
>>> phase   2   30   30   30   30
>>> phase   3 -150 -150 -150 -150
>>> phase   4  -30  -30  -30  -30
>>> phase   5  150  150  150  150
>>> phase   6   60   60   60   60
>>> phase   7 -120 -120 -120 -120
>>> phase   8  -60  -60  -60  -60
>>> phase   9  120  120  120  120
>>> phase  10   90   90   90   90
>>> phase  11  -90  -90  -90  -90
>>> vstack: max height 15
>>>
>>>
>>>
>>> I also wanted to mention the CPU usage during the decode. EbNaut uses
>>> powerful error correction and processing for message decodes. CPU usage for
>>> the decoder process was 130%, meaning one core was completely utilized and
>>> the other was 30% utilized!! Paul mentioned that this is the only amateur
>>> radio mode that uses more power to decode the message than it does to
>>> transmit the message!
>>>
>>>
>>>
>>> Congratulations to Paul and Bernd DL3JMM on a successful transmission
>>> campaign and a first for the W2NAF-KC3EEY VLF Receiver!!
>>>
>>>
>>>
>>> More about the EbNaut mode can be found here
>>> <https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fabelian.org%2Febnaut%2F&data=05%7C01%7Cnathaniel.frissell%40scranton.edu%7C280a1ea4693a45e1687508daf97d66af%7Ca8edc49a41f14c699768a7f6d7c3b8c3%7C0%7C0%7C638096614239145939%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=OSoz%2FgzgWaJAwxlEoMhhl%2BtcmHyyY73FdgSaiGksiMQ%3D&reserved=0>
>>> .
>>>
>>>
>>>
>>> Jonathan
>>>
>>> KC3EEY
>>>
>>>
>>>
>>>
>>>
>>> --
>>> Please follow the HamSCI Community Participation Guidelines at
>>> http://hamsci.org/hamsci-community-participation-guidelines
>>> <https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fhamsci.org%2Fhamsci-community-participation-guidelines&data=05%7C01%7Cnathaniel.frissell%40scranton.edu%7C280a1ea4693a45e1687508daf97d66af%7Ca8edc49a41f14c699768a7f6d7c3b8c3%7C0%7C0%7C638096614239145939%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=RLAWZ3ARIW9XZh6oJ0OLJzG5725ozMBMkcUBwW41nEM%3D&reserved=0>
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>>>
>>>
>>> --
>>> Please follow the HamSCI Community Participation Guidelines at
>>> http://hamsci.org/hamsci-community-participation-guidelines.
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>>
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