Message-ID: <56563AA4.7080606@posteo.de>
Date: Wed, 25 Nov 2015 23:48:04 +0100
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: LF: Alternative high resolution frequency source for LF
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Hmm,

Use _Spectrum Lab_ with a GPS reference signal, compensating the 
soundcard drift, and a GPS-locked mixer and you're down in the 10 uHz 
range and also ready for nearly any mode used on the band! :-)

73, Stefan

Am 25.11.2015 23:00, schrieb Andy Talbot:
> Although DDS sources seem to more-or-less dominate where high 
> resolution / accuracy is needed, there is another route that could be 
> worth investigating:   Fractional-N synthesis with addtional dividers.
>
> For example, the LMX2541  with a  10MHz reference  phase comparator 
> input will generate steps as low as 2.38Hz at its minimum internal VCO 
> frequency of 2.2GHz.  A programmable output divider goes to divide-by 
> 63, allowing steps of 0.038Hz at 35MHz .  Add a single chip binary 
> divider of 256 (for the 137kHz band)  and you're down to 150uHz steps 
> - which are completely deterministic.
>
> Since phase noise and Fract-N sidebands are hardly an issue with this 
> degree of output division, the phase comparator could be operated at a 
> much lower frequency, say 500kHz, allowing steps of  lower than 10uHz. 
>   Which is a significantly higher resolution than the 2.3mHz steps the 
> traditional AD9850 32 bit DDS offers.
>
> I've used these Fract-N devices extensively at microwaves,  see 
> http://www.g4jnt.com/LMX2541_Synth_Module.pdf ,    but haven't yet 
> turned one into an LF exciter
>
> Andy  G4JNT

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Hmm, <br>
<br>
Use <u>Spectrum Lab</u> with a GPS reference signal, compensating the
soundcard drift, and a GPS-locked mixer and you're down in the 10 uHz
range and also ready for nearly any mode used on the band! :-)<br>
<br>
73, Stefan<br>
<br>
Am 25.11.2015 23:00, schrieb Andy Talbot:
<blockquote
 cite="mid:CAA8k23QYn0i6aKS7HA=EbcUyeZH2X5HQaGXzaaa1VbV_hhrftA@mail.gmail.com"
 type="cite">
  <div dir="ltr">Although DDS sources seem to more-or-less dominate
where high resolution / accuracy is needed, there is another route that
could be worth investigating:   Fractional-N synthesis with addtional
dividers.
  <div><br>
  </div>
  <div>For example, the LMX2541  with a  10MHz reference  phase
comparator input will generate steps as low as 2.38Hz at its minimum
internal VCO frequency of 2.2GHz.  A programmable output divider goes
to divide-by 63, allowing steps of 0.038Hz at 35MHz .  Add a single
chip binary divider of 256 (for the 137kHz band)  and you're down to
150uHz steps - which are completely deterministic.</div>
  <div><br>
  </div>
  <div>Since phase noise and Fract-N sidebands are hardly an issue with
this degree of output division, the phase comparator could be operated
at a much lower frequency, say 500kHz, allowing steps of  lower than
10uHz.   Which is a significantly higher resolution than the 2.3mHz
steps the traditional AD9850 32 bit DDS offers. </div>
  <div><br>
  </div>
  <div>I've used these Fract-N devices extensively at microwaves,  see <a
 moz-do-not-send="true"
 href="http://www.g4jnt.com/LMX2541_Synth_Module.pdf">http://www.g4jnt.com/LMX2541_Synth_Module.pdf</a>
,    but haven't yet turned one into an LF exciter</div>
  <div><br>
  </div>
  <div>Andy  G4JNT</div>
  </div>
</blockquote>
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