Re: LF: 137.7770 kHz

[Michel Brunel <f5wk@mterrier.net>]

Hi Joe,

After refurbishing the 137 kHz preamp, I'm back on LF - Rx only -
The wideband 455 kHz ceramic filter has been replaced by a 600 Hz
mechanical filter, mainly to improve the RX's dynamic.
I don't know if it is any better yet ...

The frequency chirp is noticeable on the night capture. Hope you
can get rid of it soon.
The Loran-C lines are best received during the day due to a lower
band noise. They give a precise idea of the overall stability. 

73 and HTH

Michel - f5wk


Le dimanche 2 juin 2013 à 16:07:53, Jcraig écrivait :

> Hi Stefan, Markus and Group,

> Thanks for looking Stefan.  The ERP was down until the second Decca
> module was switched in at 2330 bringing the output power from 150 to
> 450 watts (3.2 amps to the aerial.)  After this the signs appeared on
> the DF6NM grabber.

> Thanks to Markus for the detailed report. The next steps are to reduce
> the 0.02 Hz chirp, frequency offset and phase glitches. I am grateful
> for your finding these and providing a progress report.

> The breadboard comprises an Oscilloquartz 8663 10 MHz DOCXO which feeds an
> AD9851 clocked at 60 MHz.  The dds programming and keying is done with
> an arduino.  The DOXCO is calibrated against WWV by averaging out the
> diurnal ionospheric doppler shifts over a period of a week.

> I think the offset could be improved by setting the DDS to 13.777 MHz
> and dividing by 100 and the phase glitches/chirps could be reduced by 
> using a better power supply for the DOCOXO.  Bumps can be seen in the
> spectrum of the DOCXO at 10 MHz which are presumably due to the
> heaters being switched on and off and causing supply voltage 
> fluctuations.

> Thanks also to Vern who is still running his grabber with strong signals
> being copied during the day.  I'll leave the TX on until tomorrow ~1000 
> utc.

> 73 and tnx agn
> Joe VO1NA





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