[hpsdr] Angelia and Hermes External Clock problem

[Stijn Nestra]

Hello Helmut ea.

Indeed Atlas is a solid platform in this regards and Hermes has some 
parts loaned from this system. But in the external clock circuitry some 
parts have been omitted. Excalibur in the Atlas system contains except 
the clock shaper also a 74ac04 buffer. This takes care of the fast 
rice-times that we seem to be missing on Hermes. The second thing this 
74ac04 does is: it protects the fpga input a bit against overvoltage 
since the 74ac04 is powered by 3.3v and not 5v.

Sincerely,

Stijn PE1RKS

Op 20-08-13 12:25, Helmut, DC6NY schreef:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Mike,
>
> you are absolutely right, an additional 3V Schmitt-trigger would be fine to
> provide a clean square pulse.  On the other hand you know that HERMES and of
> course ANGELIA are an integration circuitry of the Atlas based cards with
> solid experience  of the performance.  The small on-board TCXO always
> exhibits a short time stability of +/- 2 Hz providing a simple clipped sine
> pulse.
> I’m not responsible for the design, but I never saw a big issue in the
> current version of Hermes in daily use due to dropouts.
> BTW on my Atlas based configuration I using a external homebrew 10 MHz
> source (not identical with Excalibur), but also prophylactically equipped
> with a 3V Schmitt-trigger, hi.
>
> 73, Helmut, DC6NY
>
> -----Ursprüngliche Nachricht-----
> Von: hpsdr-bounces at lists.openhpsdr.org
> [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Mike Collins
> Gesendet: Montag, 19. August 2013 21:26
> An: hpsdr at lists.openhpsdr.org
> Betreff: Re: [hpsdr] Angelia and Hermes External Clock problem
>
> ***** High Performance Software Defined Radio Discussion List *****
>
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