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Ciao a tutti gli appassionati di MF, LF e VLF
Riccardo IW4DXW sta ottenendo in questi giorni degli splendidi risultati trasmettendo in VLF su 8270.00033 Hz (ripeto Hz!).
Infatti, come cita il Piano Nazionale di Ripartizione delle Frequenze (PNRF) pubblicato sul supplemento ordinario n. 33 alla Gazzetta Ufficiale del 23 giugno 2015 n. 143, nella tabella allegata, le frequenze da 0 a 8300 Hz, non sono attribuite ad alcune servizio. Possono quindi essere impiegate per uso scientifico come indicato nella rispettiva NOTA 3.
Riccardo, è riuscito a ralizzare una grande bobina (circa 750 mHenry) che serve a mettere in risonanza la sua antenna ad L rovesciata per MF ed LF.
Sta quindi realizzando, ogni sera, delle trasmissioni con una portante generata dal suo DDS agganciato al GPS, ottenendo quindi la stabilità necessaria e la precisione del uHz.
La sua portante è stata ricevuta, dal 'big ear' delle VLF : Paul Nicholson a Todmorden, Inghilterra a circa 1400 km (vedi spettrogramma di PN allegato)
In seguito Rick ha trasmesso una parola di 3 caratteri con la modalità EbNaut - prontamente decodificata da Paul Nicholson. Riporto di seguito quanto scritto da PN:
Riccardo wrote:
> f = 8270.00332 Hz
> Start time: 21:30:00 UTC
> Symbol period: 30 s
> Characters: 3
> CRC bits: 24
> Coding 16K21A
Copied an obviously correct message in Todmorden, UK.
Eb/N0 = +1.8 dB, symbol error rate 40.5%,
S/N -30.6 dB in 1Hz. Rank 150 in the list decoder
output.
Constant reference phase (meaning the frequency
is correct and the path was stable).
Symbol timing is correct: Eb/N0 peaks at timing
offset zero.
Noise was a little higher last night compared to
the previous night, so S/N is a bit less than
expected.
Tanti complimenti a Riccardo e buona continuazione, spero che qualche appassionato delle VLF oltre me, sia invogliato dalla tua attività e possa provare a ricevere e catturare i tuoi segnali.
A tal proposito, vorrei riportare la bellissima mail scritta da Paul Nicholson, che riassume lo spirito degli OM che si affacciano a questa parte dello spettro.
Added to the growing list of amateur achievements
at VLF
http://abelian.org/vlf/amateur-radio/
It has been a very successful season so far. I hope this
encourages more people to have a go at VLF, we need more
transmitters and receivers.
Perhaps the perception is that it is difficult? Surely not.
Don't believe all those stories you hear about how hard it is
to radiate, or how difficult it is to find a location to
receive from!
Let's see -
- Low cost. You don't need expensive SDRs or test equipment.
Your PC soundcard is signal generator, spectrum analyser,
and SDR, all in one. Transmitter is just an audio amplifier,
even a low quality one. The most expensive thing you'll buy
is a load of wire for a loading coil.
- GPS timing? £18 quid for a NEO-7 module and you know your
frequency to the micro Hertz. Buy two, you'll use them!
- Easy to build. Just audio frequency signals, nothing critical
about layout. VLF is great for the homebrew enthusiast.
- You don't need a huge ERP. 10uW and you're on the air. Your
LF antenna will probably do better than you think at VLF.
- UK Notice of Variation? No problem, a simple application form,
and if enough apply, maybe the regulators will make that easier.
- Where else can you operate at the cutting edge with such
simple equipment?
In case you thing my location here is specially good, it certainly
isn't. The mains here at the top of the Calder Valley is very
rough, terrible sidebands. All the properties around here get
their power by overhead lines at 12kV and one of the two 33kV
lines feeding Todmorden is only a km away. The nearest 12kV
line is just 120m from the E-field antenna. 140mV RMS of 50Hz
on the E-field probe and a lot of harmonics. Reception here is
bad! You can probably do better in the suburbs.
How many times per century does amateur radio find a green field
to explore? Not just a new band but a whole new frequency range.
Don't miss out on this one!
--
Paul Nicholson
--
Allego infine la foto della bobina realizzata da Riccardo.
73, Domenico IZ7SLZ
Riccardo IW4DXW sta ottenendo in questi giorni degli splendidi risultati trasmettendo in VLF su 8270.00033 Hz (ripeto Hz!).
Infatti, come cita il Piano Nazionale di Ripartizione delle Frequenze (PNRF) pubblicato sul supplemento ordinario n. 33 alla Gazzetta Ufficiale del 23 giugno 2015 n. 143, nella tabella allegata, le frequenze da 0 a 8300 Hz, non sono attribuite ad alcune servizio. Possono quindi essere impiegate per uso scientifico come indicato nella rispettiva NOTA 3.
Riccardo, è riuscito a ralizzare una grande bobina (circa 750 mHenry) che serve a mettere in risonanza la sua antenna ad L rovesciata per MF ed LF.
Sta quindi realizzando, ogni sera, delle trasmissioni con una portante generata dal suo DDS agganciato al GPS, ottenendo quindi la stabilità necessaria e la precisione del uHz.
La sua portante è stata ricevuta, dal 'big ear' delle VLF : Paul Nicholson a Todmorden, Inghilterra a circa 1400 km (vedi spettrogramma di PN allegato)
In seguito Rick ha trasmesso una parola di 3 caratteri con la modalità EbNaut - prontamente decodificata da Paul Nicholson. Riporto di seguito quanto scritto da PN:
Riccardo wrote:
> f = 8270.00332 Hz
> Start time: 21:30:00 UTC
> Symbol period: 30 s
> Characters: 3
> CRC bits: 24
> Coding 16K21A
Copied an obviously correct message in Todmorden, UK.
Eb/N0 = +1.8 dB, symbol error rate 40.5%,
S/N -30.6 dB in 1Hz. Rank 150 in the list decoder
output.
Constant reference phase (meaning the frequency
is correct and the path was stable).
Symbol timing is correct: Eb/N0 peaks at timing
offset zero.
Noise was a little higher last night compared to
the previous night, so S/N is a bit less than
expected.
Tanti complimenti a Riccardo e buona continuazione, spero che qualche appassionato delle VLF oltre me, sia invogliato dalla tua attività e possa provare a ricevere e catturare i tuoi segnali.
A tal proposito, vorrei riportare la bellissima mail scritta da Paul Nicholson, che riassume lo spirito degli OM che si affacciano a questa parte dello spettro.
Added to the growing list of amateur achievements
at VLF
http://abelian.org/vlf/amateur-radio/
It has been a very successful season so far. I hope this
encourages more people to have a go at VLF, we need more
transmitters and receivers.
Perhaps the perception is that it is difficult? Surely not.
Don't believe all those stories you hear about how hard it is
to radiate, or how difficult it is to find a location to
receive from!
Let's see -
- Low cost. You don't need expensive SDRs or test equipment.
Your PC soundcard is signal generator, spectrum analyser,
and SDR, all in one. Transmitter is just an audio amplifier,
even a low quality one. The most expensive thing you'll buy
is a load of wire for a loading coil.
- GPS timing? £18 quid for a NEO-7 module and you know your
frequency to the micro Hertz. Buy two, you'll use them!
- Easy to build. Just audio frequency signals, nothing critical
about layout. VLF is great for the homebrew enthusiast.
- You don't need a huge ERP. 10uW and you're on the air. Your
LF antenna will probably do better than you think at VLF.
- UK Notice of Variation? No problem, a simple application form,
and if enough apply, maybe the regulators will make that easier.
- Where else can you operate at the cutting edge with such
simple equipment?
In case you thing my location here is specially good, it certainly
isn't. The mains here at the top of the Calder Valley is very
rough, terrible sidebands. All the properties around here get
their power by overhead lines at 12kV and one of the two 33kV
lines feeding Todmorden is only a km away. The nearest 12kV
line is just 120m from the E-field antenna. 140mV RMS of 50Hz
on the E-field probe and a lot of harmonics. Reception here is
bad! You can probably do better in the suburbs.
How many times per century does amateur radio find a green field
to explore? Not just a new band but a whole new frequency range.
Don't miss out on this one!
--
Paul Nicholson
--
Allego infine la foto della bobina realizzata da Riccardo.
73, Domenico IZ7SLZ
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