47418Re: Advice needed with Ensemble RXTX
- Sep 2, 2010Hi Sid,
Thanks for that correction, that slipped my mind.
Well, it was early in the morning here and I had only just got out of bed. I just have a few minutes to try and answer a few emails and questions before setting off for work, so not really thinking too much at the time, that's my excuse, and I am sticking to it :)
73, Bob G8VOI
--- In firstname.lastname@example.org, "w7qjq" <sbjknox@...> wrote:
> --- In email@example.com, "g8voip" <g8voi.reeves59@> wrote:
> > The is nothing 'funny' about there being minor frequency differences between different Si570 devices. If you purchased two crystals you would not expect them to be identical. If you take a look at the data sheet for the Si570, you will see the frequency source is a variable oscillator in the mid GHz region/ Producing that on such a small piece of silicon will invariably produce a spread of tolerances. That's exactly why the calibration feature is provided in the firmware.
> > 73, Bob G8VOI
> Minor correction needed here...it is not the variations in the GHz VCO that cause each Si570 to require calibration but rather the variations in the (approx)114 MHz internal reference xtal oscillator. The GHz VCO is operating in a closed loop (PLL). The Si570 frequency accuracy and drift (with time and temperature) is entirely determined by the stability of the reference xtal.
> 73, Sid W7QJQ
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