[time-nuts] filtering a 10Mhz frequency standard?

shalimr9 at gmail.com shalimr9 at gmail.com
Tue Dec 13 11:04:45 EST 2011


If your intent is to take full advantage of the long term as well as short term stability of a reference oscillator, the best approach is a low pass filter that will have small (and stable) phase shift at 10 MHz.
Most bandpass filters will have enough temperature sensitivity of the phase shift through the filter to degrade the performance of an Rb. It may look fine on the scope but would not give you good long term adev.

If you don't care about long term stability, you probably do not need an Rb in the first place.

If you only need good long term frequency stability and phase (or absolute time) is of no concern, then the type of filter (and whether there is a filter or not) does not matter.

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Chris Albertson <albertson.chris at gmail.com>
Sender: time-nuts-bounces at febo.com
Date: Mon, 12 Dec 2011 17:54:09 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: [time-nuts] filtering a 10Mhz frequency standard?

What is the best practice for filtering a 10Mhz sine wave frequency
standard?   I've read that you can do more harm than good. Filter
parts  (caps, resistors and so on) are all temperature sensitive. But
all those $40 Rb oscillators are putting out a pretty rough looking
sine wave.

Are some types of filters better.  I thought about a crystal filters.

-- 

Chris Albertson
Redondo Beach, California

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