First Amateur VLF Transmission Detected at the W2NAF-KC3EEY VLF Receiver!
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Jonathan
Jan 18, 2023, 12:57:00 PM1/18/23
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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:
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
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
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
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.
Jonathan
KC3EEY
Jonathan
Jan 18, 2023, 2:12:03 PM1/18/23
to TangerineSDR Listserv, Unknown
Hi All,
more attenuation than the west-to-east."
Using LWPC modeling, Paul determined the following about the propagation path between DL3JMM and Springbrook:
"Using LWPC on the path DL3JMM to Spring Brook Township at
8270Hz at midnight UTC, the east-to-west direction has 10.6dBmore attenuation than the west-to-east."
Jonathan
KC3EEY
Robert McGwier
Jan 18, 2023, 2:34:29 PM1/18/23
to ham...@googlegroups.com, TangerineSDR Listserv
Congratulations!
Bob N4HY
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Dr. Robert W McGwier, Ph.D.
Adjunct Faculty, Virginia Tech
Adjunct Faculty, Virginia Tech
Affiliated Faculty, University of Scranton
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ARDC Member of Board
N4HY: ARRL, TAPR, AMSAT, EARC, CSVHFS
Sky: AAVSO, Sky360, explorescu.org, Skyscrapers
David Eckhardt
Jan 18, 2023, 2:42:48 PM1/18/23
to ham...@googlegroups.com, TangerineSDR Listserv
Excellent. Wish I had the drive to participate, but at 76 YO, a lot of my get-up-'n-go has gotten up and departed.
Given this, possibly, and once again, amateur radio is paving the road to reducing the massive and powerful installations the Navy uses for comm. with the submarines? Yes, I periodically monitor those comms. among many other sources of opportunity.
Dave - WØLEV
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/CA%2BK5gzd9a1kSEeP5V23ZkRJxnvWVDT2LT5Fq19FVcKqkmRqtGA%40mail.gmail.com.
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Dave - WØLEV
Dr. Nathaniel A. Frissell Ph.D.
Jan 18, 2023, 3:34:35 PM1/18/23
to ham...@googlegroups.com, TangerineSDR Listserv
That is wonderful news, Jonathan! Congratulations!
73 Nathaniel W2NAF
From: ham...@googlegroups.com <ham...@googlegroups.com>
On Behalf Of Jonathan
Sent: Wednesday, January 18, 2023 12:57 PM
To: TangerineSDR Listserv <tanger...@lists.tapr.org>; Unknown <ham...@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.
Jonathan
KC3EEY
--
John Magliacane
Jan 18, 2023, 5:51:15 PM1/18/23
to ham...@googlegroups.com
On Wednesday, January 18, 2023, 12:57:02 PM EST, Jonathan <emum...@gmail.com> wrote:
> 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!
> 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!
Nice! Congratulations, Jonathan!
73 de John, KD2BD
73 de John, KD2BD
Julius Madey
Jan 18, 2023, 10:26:53 PM1/18/23
to ham...@googlegroups.com
Congratulations Jonathan and Nathaniel ..!
Another first ?
73,
Jules -K2KGJ
73,
Jules -K2KGJ
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/PH0PR03MB70176245EF58BFB49191EDCCF2C79%40PH0PR03MB7017.namprd03.prod.outlook.com.
Jonathan
Jan 22, 2023, 1:02:44 AM1/22/23
to ham...@googlegroups.com
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
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!
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
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/d5f88601-08d6-bf92-d000-389acc424a1a%40gmail.com.
Jonathan
Jan 22, 2023, 1:17:30 AM1/22/23
to ham...@googlegroups.com
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
Jonathan
Jan 22, 2023, 1:07:14 PM1/22/23
to ham...@googlegroups.com, TangerineSDR Listserv
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.
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:
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
Dennis Williard
Feb 26, 2023, 7:13:12 PM2/26/23
to HamSCI
Just saw this message and i was wondering what the freq. is...
Jonathan
Feb 26, 2023, 8:11:34 PM2/26/23
to HamSCI
Hi Dennis,
I mentioned the frequency in the first paragraph. You read it right, it's
8270.03 Hz.
Message decoding is not done in real time like traditional
amateur radio, it's done after the transmission has taken place with
recorded spectrum fed into a signal processing chain to a decoder.
Jonathan
KC3EEY
On Sun, 26 Feb 2023, Dennis Williard wrote:
> Date: Sun, 26 Feb 2023 16:13:12 -0800 (PST)
> From: Dennis Williard <ka3...@gmail.com>
> Reply-To: ham...@googlegroups.com
> To: HamSCI <ham...@googlegroups.com>
> Subject: [HamSCI] Re: First Amateur VLF Transmission Detected at the
> W2NAF-KC3EEY VLF Receiver!
>
>> More about the EbNaut mode can be found here <http://abelian.org/ebnaut/>.
>
I mentioned the frequency in the first paragraph. You read it right, it's
8270.03 Hz.
Message decoding is not done in real time like traditional
amateur radio, it's done after the transmission has taken place with
recorded spectrum fed into a signal processing chain to a decoder.
Jonathan
KC3EEY
On Sun, 26 Feb 2023, Dennis Williard wrote:
> Date: Sun, 26 Feb 2023 16:13:12 -0800 (PST)
> From: Dennis Williard <ka3...@gmail.com>
> Reply-To: ham...@googlegroups.com
> To: HamSCI <ham...@googlegroups.com>
> Subject: [HamSCI] Re: First Amateur VLF Transmission Detected at the
> W2NAF-KC3EEY VLF Receiver!
>
> Just saw this message and i was wondering what the freq. is...
>
>
>>
>> Jonathan
>> KC3EEY
>>
>>
>>
>
> --
> Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/275ca8b6-4044-4fec-8e57-fe614ca2ec39n%40googlegroups.com.
>> Jonathan
>> KC3EEY
>>
>>
>>
>
> --
> Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
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