Date: Mon, 3 Jun 2013 16:31:17 -0230 (NDT)
From: jcraig@mun.ca
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: 137.7770 kHz
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Thank-you Michel for the helpful report.
It seems as if your RX is working well.

73
Joe VO1NA

On Mon, 3 Jun 2013, Michel Brunel wrote:

> 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 The wideband 455 kHz ceramic filter has been replaced by a 600 Hz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 =E0 16:07:53, Jcraig =E9crivait :
>
>> 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
>
>
>
>
>
>> This electronic communication is governed by the terms and conditions at
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>
>
>
>
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