[time-nuts] Things to look for when buying a few FE-5680A's?

Bob Camp lists at rtty.us
Thu Jan 26 12:49:29 EST 2012


The PPS would indeed be off if you move the 10 MHz (no matter how you do
it). The range of the output relative to the 380 Hz digital tune range is
restricted by the pull range of the VCXO. There have been plots posted
showing the pull range, and it's (lack of) centering. 

No need to re-shoot any firmware.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Chris Albertson
Sent: Thursday, January 26, 2012 12:36 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Things to look for when buying a few FE-5680A's?

On Thu, Jan 26, 2012 at 9:13 AM, Bob Camp <lists at rtty.us> wrote:
> Hi
> If you *need* to lock one of the new FE-5680's 10 or 20 Hz high, you
> probably can adjust the cap on the VCXO center it's range up there.

The frequency division is done by digital logic inside a CPLD and
you'd need to re-program the firmware.  I think people have found that
these new FE5680s don't lock if you move far from 10MHz and you can't
get more than a few hundred Hz from 10Mhz by analog adjustment.

The "option 2" that is in the book is different from the fine scale
adjustment the current $40 can do.   the true option two units can be
programmed over a range of many MHz by sending RS232 commands but the
current units can only by programmed over rs232 withina very narrow
range about like you'd find on a typical OCXO.

I think if you want a wide range oscillator you are best using a DDS
chip whos clock is locked to the FE5680 or a Thunderbolt.   The
FE5680's advantage over a t-bolt is portability.

Chris Albertson
Redondo Beach, California

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