Re: LF: talking about EbNaut

[Markus Vester <markusvester@aol.com>]

Thank you Domenico and Tom for sharing this interesting communication with us! 

The QTH of DK1IS is actually not far from mine, we're about 50 km apart. That might open some nice options for LF "nanowatting" experiments, e.g. transmitting on a small handheld or buried ferrite antenna. It would also be an interesting range to get started on VLF...

> Up to now the 1pps pulse only drives a LED - if its flashes coincide with the ticks of my mechanical but DCF77-controlled alarm clock, I can be sure that the Jupiter has synchronized
... exactly the same method is used here ;-)

73 and good luck,

Markus (DF6NM in JN59NJ)
 

-----Ursprüngliche Mitteilung-----
Von: IZ7SLZ <iz7slz.domenico@gmail.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Do, 1 Dez 2016 9:32 pm
Betreff: LF: talking about EbNaut

Dear Group,

i want to share with the group some informations on EbNaut recently exchanged between me and Tom, DK1IS. He hold in his shack some marine radios that are almost ready for this mode.
   

Domenico, IZ7SLZ wrote:

Noted your excellent setup in qrz.com. So maybe you are familiar with  marine radios.
Mine is composed by a Sailor exciter s1301L and a Standard Radio reserve transmitter  ST86A used as PA (120W).
Receiver is a JRC nrd-92m.

Both equipment synthetizers are steered with an external homemade 10 MHz GPDO.
This setup is working fine also on LF and i use it in EbNaut experiments.
Since you can control your Hagenuk tx and rx with a Rb oscillator, may i invite you in some EbNaut test or qso?

Tom, DK1IS wrote:

Mine is composed by a Sailor exciter s1301L and a Standard Radio reserve transmitter  ST86A used as PA (120W).
Receiver is a JRC nrd-92m.

Nice radios in either case - I just downloaded the specs. Ah, the S1301L is the MF extended version: fine! But like with my EX1001 the smallest tuning step is 100 Hz - this was the reason for me to let the exciter work on 13.6 MHz resp. 4.76 MHz and divide the output frequency down by 100 resp. by 10. Btw, from Sailor I use their fb fiber core rubber antenna insulators, 60 cm long and very robust, for ships - they stand the 8.9 kV rms LF voltage on my Marconi since 15 years in every weather. I bought them for peanuts at a marine radio shop during holidays on Bornholm island, Denmark.

Both equipment synthetizers are steered with an external homemade 10 MHz GPDO.
This setup is working fine also on LF and i use it in EbNaut experiments.
Since you can control your Hagenuk tx and rx with a Rb oscillator, may i invite you in some EbNaut test or qso?

Originally the EX1001 has no external reference input but a rather good central TCXO at 9 MHz.  I added a PCB with 10 MHz input from the rubidium oscillator, dividing down to 1 MHz and then filtering out the 9 MHz harmonic with two CB xtals. Works fb and can be switched over to the primary TCXO.
EbNaut: thanks for the invitation, Domenico, but so far no experiences - being not the real PC freak up to now I avoided time and effort to get in process. May be the appetite will come later ...

Domenico,  IZ7SLZ wrote:

Just for your information (and hoping to let you hungry :-)) i briefly describe my  EbNaut arrangements:

First of all, S1301L Exciter synthetizer has been modified with a 10 MHz OCXO instead of its original TXCO. I added a simple PLL that controls the voltage of  the "frequ. adj." pin of this OCXO by comparing the 10 kHz reference signal (coming from the GPS) and 10 kHz from the divider.

Yes, S1301L has only 100 Hz resolution. I studied its circuit diagram and noted that it is not very difficul to obtain at least 10 Hz resolution by adding another loop in the synthetizer. But i never performed such modifications. This becouse  i'm using a PCI slot sound card with good specifications that, after Spectrum Lab calibration process (using 1pps signal  from the same GPS), gives an output audio very precise and almost without glitches.
The audio card is a PHASE 88 PCI from Terrasoniq (German design).

So i use this audio to modulate the exciter in USB mode and i can obtain the precision and resolution needed (on milliHz).
Ok, this is not the best arrangement to obtain TX signals; Markus and Wolf never suggested it. But, thanks to Spectrum Lab great job,  it works,  as confirmed by many EbNaut decodes and OP32 measurements using DF6NM grabber.

To obtain EbNaut bpsk modulation i just feed the exciter with a tone (around 1500 Hz - depends on final QRG) generated by Spectrum Lab via a ring modulator composed by 2 audio transformers and 4 diodes. Ring modulator is switched  by the two RS232 signals ( DTR - RTS) managed by EbNaut-tx program.

In Receiving side, i have modified the JRC NRD-92M to accept a 10 MHz TTL signal from the Sailor synthetizer (after small buffering). So receiver  is now calibrated enough for EbNaut. Rx audio goes to Spectrum Lab that performs some filtering, NB and gives a .wav file prepeared for EbNaut-rx decode program.

The time synchronization is also vital for EbNaut. I'm using a small software (written by me)  that decodes GPS telegrams and according the 1pps signal, sets the PC time periodically.

GPS in use is a Rockwell Jupiter (coming from an out-of-order vintage AIS DEBEG3400).

Tom, DK1IS wrote:

Thanks for the most interesting infos - to become QRV in EbNaut seems to be less than complicated I thought . Nice idea to overcome the 100-Hz-steps of your exciter by modulating it with a suitable audio frequency which is necessary for EbNaut anyway! I could do it with my EX1001, being also a SSB/CW/RTTY-exciter, too and could even avoid the frequency deviders with it - nice approach. But due to the filter passband and the modulation one hasn´t a direct frequency readout on the exciter any longer - shouldn´t be a real problem. Before going this way I would have to check the phase characteristic of the EX1001 audio/modulation path; in a pinch I could use your ring modulator technique too.

Btw, for my GPS controlled units I also use the Rockwell Jupiter 10-kHz-output. Up to now the 1pps pulse only drives a LED - if its flashes coincide with the ticks of my mechanical but DCF77-controlled alarm clock, I can be sure that the Jupiter has synchronized - archaic, isn´t it ?

So, a lot to think about. Perhaps one fine day we will meet in EbNaut ...



73 all, Domenico iz7slz