Hi Stefan
Very nice experiment down there. Congratulations again :-)
I have been trying to track your calculations but got lost with your antenna
voltage figures
At 6470Hz with L=1.29H that should be an antena reactance of 52K Ohm, right ?
Then at 270mA antenna current that should be much more than 3.2KV ?
Sure I'm missing something :( (coil losss, etc)
Another question about your multi turn Rx loop. Any proteccion for nearby
lightings ?
I'm planning to set a VLF Rx here and concerned about this. Would be a good
idea to
short the loop with a relay in case of nearby storm to protect the NPN and Rx
chain ?
73 de Luis
EA5DOM
________________________________________
De: [email protected] [[email protected]] en
nombre de DK7FC [[email protected]]
Enviado: domingo, 31 de julio de 2016 0:28
Para: [email protected]; Renato Romero
Asunto: Re: ULF: Key down signal on the 101 km band, still on the air
Hi all,
The 100 nW ERP 2970 Hz carrier has been on the air since 26th of June,
13 UTC. The transmitter phase has been stable since this time. There
were only a few very short interruptions, 90 minutes on the 17th of July
and then about 5 hours (5:45....11 UTC) on the 21st of July.
So it has been on the air since nearly 5 weeks.
The signal is still on the air but tomorrow 8 UTC i will do a frequency
shift of + 2.5 mHz. Later i will do an EbNaut test.
If someone still want to integrate the overall transmission into one
peak, tomorrow, 31th July 8 UTC will be the stop time.
In a few days i will then come back with a 6 dB stronger signal:
Coming from the LF world we assume that using a parallel capacitor to
the antenna is not a good idea. More C will mean less L, so you need
less wire and could think that this lowers the losses. But higher
currents are then needed which will cause even higher losses...
Thus i didn't consider to use a parallel C on ULF too. BUT on ULF, with
voltage limited systems it can be a good choice!
I run the yoghurt cup coil at 270 mA antenna current on my 470 pF
antenna at 6470 Hz. So it must have 1.29 H. So at 2970 Hz and 270 mA it
must have 6.5 kV! Currently i have about 3.2 kV. So with this
alternative matching i will get a 6 dB stronger signal.
I will then need 1.76 nF parallel to the antenna.
My 17 km distance experiment is running now! I have installed the loop
antenna somewhere in JN49KM. The Raspy is now recording stereo wav files
to the 32 GB USB stick... I'm using 2x 7 Ah lead acid gel batteries for
the supply. 1PPS+NMEA is used on the right channel.
73, Stefan
Am 17.07.2016 19:36, schrieb DK7FC:
> Hi all,
>
> The signal is on the air since > 3 weeks now :-)
> Paul, any results in a bandwidth < 1 uHz ?
>
> Renato Romero has started a spectrogram of 1.26 uHz FFT bin width and
> a 3000 min / pixel scroll rate :-)
>
> Between 16...17:30 UTC today the transmitter stopped for some reason.
> I have restarted the PC. Now the signal is on the air again. The phase
> of the signal is not just constant, it is even the same as before the
> PC restart :-) So the loss of just 90 minutes doesn't really hurt...
>
> 73, Stefan
>
> Am 06.07.2016 08:48, schrieb Paul Nicholson:
>>
>> Stefan wrote:
>>
>> > The carrier is on the air since 9 days now, without
>> > an interruption.
>>
>> Nothing is visible, not even the beginning of a peak at 2970,
>> down to bandwidths of 1.36 uHz.
>>
>> I continue to experiment with the settings of filters and
>> sferic blanker. The noise floor is too high, averaging
>> 0.023 fT in 1.36 uHz even after blanking the noisy periods.
>> It should be a lot lower than that. If I can fix that problem,
>> we may see the signal appear.
>>
>> --
>> Paul Nicholson
>> --
>>
>
|
