Re: VLF: carrier at 8270.003

[Riccardo Zoli <riccardozoli80@gmail.com>]

Hi VLF,

Stefan and Paul, many thanks for reports.

Ok, Stefan, great! I'm on air again (in this moment with 620 mA) testing a configuration based on your suggestions.

I made a simple watch plot with antenna current and phase correction (the antenna is now a little shacked, it's a quite windy day here), but I have to optimize the protection statements.

A screenshot of SpecLab attached.

Have a good day

73 de Riccardo IW4DXW

Il Gio 26 Apr 2018, 17:54 DK7FC <selberdenken@posteo.de> ha scritto:

Hi Riccardo,

Your signal is well visible here on my grabber http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html

Am 26.04.2018 13:04, schrieb Riccardo Zoli:

Hi VLF,

A new carrier test is running with about 610mA.

Now, with last SL version, the PLL configuration made by Markus seems to works well here, the phase is stable. I started this test yesterday at about 10:00 UTC.

I'm looking for an adequate conditional statement that permits to inhibit the audio (and the TX) in case of an excess of antenna current drop. Any suggestion?

Yes, sure, this is what i'm using all the time here.
First you need to calculate the antenna current from the signal level

I use: s=1820*(10^((peak_a((sgf-10),(sgf+10)))/20))
s= antenna current in mA
sgf=transmit frequency (signal generator frequency)
1820 is just a calibration factor to calibrate the value to mA.
The If condition is 1, so it is executed on each FFT, which means each 200 ms.
Then i define a traget current with the parameter d: d=600 (for example)
Next i define a current limit L, say 100 mA
Now if the actual current s drops L mA below the target value d, then another parameter e, which is a counter level, is increased.
After 200 ms the measurements are repeated and if the current is still to low, e is increased again.
Oh and there is another parameter c, which regulates the output amplitude.
If e exceeds a certain value (i choose 5), the c is set to 0, so the output amplitude becomes 0.

Actually the complete procedure is much more complex, i just described the safety function.
If you like, i can send you a usr file for TXing carriers and EbNaut...

73, Stefan

My current VLF condx attached.

All the best

73 de Riccardo IW4DXW

PLL_curr.JPG
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