Re: LF: F5WK EbNaut

[Markus Vester <markusvester@aol.com>]

Hi Michel,

your signal is not weak at all, surely good enough for comfortable QRSS3 reading here. 

Regarding overcurrent trip: I found that for safest operation of a class-D PA, the antenna impedance should be presented as a series resonant circuit to the transistors, because that will have high impedance for any out-of-resonance spectral components. Then during phase reversals, the current will experience a dip rather than a peak. The impedance condition depends on the total phase shift of the matching circuits and low pass filters, which should ideally be 0 or 180°. However feeding into a 50-ohm loading coil tap (or through certain PI- or T-filters) tends to have around 90°, transforming series resonance into parallel resonance, and presenting a short-circuit to the PA for out-of-band exciation.

Tonight there seems to be a (somewhat weaker) trace on your QRG again, are you still sending EbNaut?

Best 73,
Markus (DF6NM)



-----Ursprüngliche Mitteilung-----
Von: Michel Brunel <f5wk@mterrier.net>
An: Domenico IZ7SLZ <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 28 Sept 2016 7:13 pm
Betreff: Re: LF: F5WK EbNaut

Hi,

Big thanks to Domenico, Markus and Stefan for their successful decoding of my EbNaut transmissions.
Ebnaut decoding is not an easy task especially with weak signal.

I fear my GPSDO frequency was not as accurate than expected. I had the bad idea to use a low cost GPS antenna wich performed
not as good as the professional grade antenna I used for tests at home. Thus some jitter and phase jumps depending on GPS constellation position.
As a "proof of concept" I made Loran-C records during the day  using the ebnaut setup and results are sometime  good sometime not so good.

The transmitter overcurrent was randomly  triggered by the phase reversal. Bpsk modulation is performed synchronously by exclusive OR gates, between the D flip-flop and the MOS drivers. Phase reversal is like changing the frequency for a very short time, which leads to a current pike due to the high Q of the LF antenna. Decision was taken to bypass the overcurrent detection.
The good way to do bpsk modulation is with a suitable DDS such as AD9852. 

I found the antenna performs poorly at LF since the radials are burried in a sandy soil, as time goes on. No big deal for ebnaut though.

A lot of things to improve for my next LF campaign, 

73,
Michel - f5wk/P 

-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 28 Sept 2016 2:42 pm
Betreff: Re: LF: F5WK EbNaut

Hi LF,

I tried the 20 UTC transmission (didn't thry the others) and got a nice decode, see attachment.
Congrats to the successful transmission. I will join in too in some time :-)

73, Stefan

Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 28 Sept 2016 12:33 pm
Betreff: Re: LF: F5WK EbNaut

Also very nice decodes here:

2016-09-27  "F5WK IN99EF"

start         Eb/N0 (db)
 UT       symbol carrier 

16:15:01   8.5   17.4 (aborted after 9 min)
16:45:01  71.1   22.2
17:00:01  17.7   20.3
17:30:01  17.7   21.3
18:00:01      nil         (aborted after 2 min)
18:30:01  17.7   21.7
19:00:01  71.1   21.4
19:30:01  17.7   23.1
20:00:01  17.7   23
20:30:02  71.1   23.9 (1 sec later)
21:00:01  10.4   14.1
21:30:01  16.7   20.7
22:00:01  14.7   15.8

Michel's transmissions are also well visible as blue dashes in the daily grabber archive:
http://df6nm.bplaced.net/LF/archive/2016/20160927.jpg
http://df6nm.bplaced.net/LF/archive/2016/20160926.jpg

Best 73,
Markus (DF6NM)

Le mercredi 28 septembre 2016 à 11:08:55, Domenico écrivait :

 

Hello LF, EbNaut test signals from Michel F5WK/P in Normandy  has been received also here in JN80NU (QRB = 1700 km). This is the list of my decodes: DATE           TIME UT     Time OFFSET [s]       EbN0[dB]         Carrier EbN0[dB]     Rk 26-09-2016     21:30             0                             0.9                        1.9                 0       message:F5WK JN18HP ------------------------------------------------------------------------------------------------------------------------------ 27-09-2016     18:30             1                            5.6                         6.7                 0   27-09-2016     19:00             1                            7.8                         9.0                 0      27-09-2016     19:30             1                            5.1                         5.8                 0   27-09-2016     20:00             1                            6.1                         6.7                 0   27-09-2016     20:30             1                            6.5                         6.7                 0   27-09-2016     21:00             1                           NIL 27-09-2016     21:30             1                            3.7                         4.6                 0   27-09-2016     22:00             1                            3.0                         4.4                 0    message: F5WK IN99EF receiver in use: JRC NCR-92M with 10 MHz GPDO with 7m passive whip antenna. Congratulation Michel for your EbNaut nice going; can you describe your setup ? 73, Domenico IZ7SLZ On 27 September 2016 at 00:22, Markus Vester <markusvester@aol.com> wrote: Michel F5WK is running EbNaut tonight! He's got a strong and stable Signal, and the 21 UT sequence produced a successful decode here. Thanks to Michel for the test transmissions, and to Domenico IZ7SLZ for kindly passing on the Information. Best 73, Markus (DF6NM) ---------- Forwarded message ---------- From: "Michel Brunel" <f5wk@mterrier.net> Date: 26 Sep 2016 18:41 Subject: Re: Need some help ! To: "Domenico IZ7SLZ" <iz7slz.domenico@gmail.com> Cc:  Hi  Domenico, I'm now ready to transmit an ebnaut test at UTC 18:00:00 - 137489.999179 Hz - message length 11 - Coding  8K19A - symbol period 1.0 - duration  13:20:00 Estimated ERP: 100 mW  Michel - f5wk/P

--