Re: VLF: Transmission 8270 Hz - first pixels

[DK7FC <selberdenken@posteo.de>]

Hello Alex, VLF,

Hm, maybe there is something in 47 uHz, but still not significant.

I'm going to transmit for a much longer time, probably throughout the night and tomorrow.

The security check in SpecLab is programmed and active so i can sleep better.
The check is easier than i thought at first:
If (save=1)*(r<-50) then e=e+1
If (r>-50)*(e>0) then e=e-1
If e>15 then a=0.5

In scheduled actions enable 'save=1' a few seconds after the transmission.
r = Regeldifferenz = s-d
s = actual antenna current
d= set value antenna current
a=0.5 => carrier off

Each 200 ms these lines are executed. So if for example there is a remaining flash over or the coil dropps, the resonance is lost, the antenna current drops. After 15*200 ms, the carrier will be stopped.

Also the coil should be relatively warm, so it stays dry in a foggy environment. I'm going to have a look again on it...

Here's an image of the coil, running at 25 kV during the photo was taken: https://dl.dropboxusercontent.com/u/19882028/VLF/8270Hz%20new%20coil.jpg
It has 3 layers, 740 mH and a Q(measured at 8270 Hz) of 122.

73, Stefan


Am 27.01.2017 16:46, schrieb Alex K:

Hello VLF, Stefan,
in attacment are my screenshots of 47uHz and 470uHz
Grabber will run to Mondey.
73 de Alex/rn3aus

Пятница, 27 января 2017, 16:58 +03:00 от DK7FC <selberdenken@posteo.de>:

Hello Markus,

The coil+antenna is running at 25 kV now. And quite relaxed! Not a trace of partial discharges on the top of the coil. It looks like this can be done regularly from now on, so don't stress with your observations. However the QRN is low now and phase variations are better to observe... There was an interesting phase change on Pauls grabber as well. When moving the bearing there is a strong dip in the signal strength, looks almost unrealistic.

See the latest plots at http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/TX.png The antenna current is held exactly!
I even thought about a protection like: If antenna current deviation > 50 mA => Start timer (2 sec) => If current deviation still > 50 mA, then stop transmitting; else, ignore.

A signal already builds up in Italy too: http://www.vlf.it/cumiana/livedata.html 20 dB SNR in 47 uHz!
I hope that Alex/RN3AUS will pick it up as well.

The recent problem (my dropping antenna current) was rather a PA problem than a coil problem, fortunately. The PA runs without any problem at up to 5 A DC / 25V. But now i'm trying to strech the limits and this leads to working point instabilities which led to a partly faulty FET (IRFP064N). With this faulty FET i've done the 2970 Hz experiment last week ;-) But now it has been replaced. I also increased the source resistors from 0.1 Ohm to 0.22 Ohm. But this reduces the gain significantly. So i increased the supply voltage of the drive OP AMP from 12V to 25V. It still doesn't really work. Thus i'm just running 600 mA now ;-) With 700 mA i can generate another 1.33 dB whch can be quite significant in distances > 1000 km...

73, Stefan


Am 27.01.2017 14:13, schrieb Markus Vester:

Hi Stefan,

thanks for the invitation. Three stations simultaneusly on air would be cool, just like in the old days on 8970. My antenna is up, but today I'd rather make use of your strong carrier to observe the diurnal variation. Looks like we've already entered the midday minimum. Maybe I should set up another instance to observe the phase evolution as well.

There's also some directional variation in Todmorden: After 8 UT, your carrier is better at 90° azimuth but lacking at 130°.  

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 27. Jan 2017 13:37
Betreff: Re: VLF: Transmission announcement for 8270 Hz

Hello Uwe,

Your signal looks nice on Pauls grabber.

Is the new ALU tower higer than the tree before? Did you ground it to
the VLF earth? Are you now getting more antenna current? How much?

Markus, will you join us on the 36 km band? :-) As far as i remember
there were never 3 amateur stations active on VLF to the same time :-)

73, Stefan



Am 27.01.2017 12:55, schrieb dj8wx@t-online.de:
> I swirched the carrier on 8270Hz off, trying to receive the DK7FC carrier.
> 73
> Uwe/dj8wx
>
>
>
> -----Original-Nachricht-----
> Betreff: Re: VLF: Transmission announcement for 8270 Hz
> Datum: 2017-01-27T12:32:06+0100
> Von: "DK7FC"<selberdenken@posteo.de>
> An: "rsgb_lf_group@blacksheep.org"<rsgb_lf_group@blacksheep.org>
>
> Hello Mike,
>
> I'm sorry, it was late in the night and i was already a bit sleeping it
> seems :-)
>
> I am transmitting RIGHT NOW! So give it a try :-)
> Watch the grabbers to see whats actually going on...
>
> 73, Stefan
>
> Am 27.01.2017 12:03, schrieb Mike Dennison:
>
>> I am confused by this announcement. From the date stamp, Stefan seems
>> to be announcing that he will transmit on Saturday, but Markus
>> reports him on Friday.
>>
>> Which day will Stefan transmit his carrier? I am keen to receive but
>> it takes me a few hours to start up my VLF receive system.
>>
>> Mike, G3XDV
>> ===========
>>
>>
>>
>>> Nice signal here in Nuernberg, ~ 15 dB SNR in 477 uHz. No idea what
>>> caused the gap in the trace around 8 UT.
>>>
>>> Paul's spectrogram currently shows both carriers, 8270.000 and
>>> 8270.005 Hz.
>>>
>>> Best 73,
>>> Markus
>>>
>>>
>>>
>>>
>>>
>>>
>>> -----Ursprüngliche Mitteilung-----
>>> Von: DK7FC<selberdenken@posteo.de>
>>> An: rsgb_lf_group<rsgb_lf_group@blacksheep.org>
>>> Verschickt: Fr, 27. Jan 2017 2:45
>>> Betreff: VLF: Transmission announcement for 8270 Hz
>>>
>>>
>>> Hi VLF,
>>>
>>> Tomorrow starting 7 UTC i'm going to run a carrier on 8270.005 Hz. It
>>> will run for a few hours during the low QRN period. Just in case
>>> someone wants to try to receive...
>>>
>>> 73, Stefan
>>>
>>> PS: 600 mA antenna current so far.
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 2016.0.7998 / Virus Database: 4749/13841 - Release Date:
>>> 01/26/17
>>>
>>>
>>>
>>
>>
>>
> 
>
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