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

John Beale beale at bealecorner.com
Thu Jan 26 01:28:41 EST 2012

> On 1/22/2012 12:49 PM, Chris Albertson wrote:
>> The current batch of (about) $40 units are different from what was
>> available a year ago. These new ones require 5V DC input in addition
>> to 15V and can only be programmed via RS232 a few Hz away from 10MHz.
>> So they are only good for use as a 10MHz reference
>> "Option 2" in the book refers to a different type FE5380 that can be
>> programed over a very wide range of several MHz. I think these are
>> still being sold on eBay but not for $40. They seem to be over $100.

In the manual I have (see below) "Option 2" is in fact what I got for about 
$40. This is RS-232 control with very fine resolution, but limited range 
(10 MHz with a span of +/- 383 Hz according to the manual, although one I 
tested won't actually stay locked much above 1% of that span).  The very 
wide range version is a different option, perhaps Option 08 (Customer 
specified frequency, 1 Hz - 20 MHz).



Table 1: "Option Summary"
Option 02   Remote Digital Control - RS-232; Resolution: 1.8 x 10-7Hz

"Frequency Adjustment" Section 2-3
The FE-5680A output frequency can be adjusted digitally over the RS-232 
interface (pins 8 and 9). This feature is available as option 2, and is not 
available on units purchased without this option. The frequency can be 
adjusted with a resolution of 1.7854E-7 Hz. For an FE-5680A device with an 
output frequency of 10 MHz, this corresponds to a relative frequency 
setting resolution of 1.7854E-14.

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