[eagle] Re: 10 MHz Phase Noise

Juan Rivera juan-rivera at sbcglobal.net
Wed Jul 11 16:55:44 PDT 2007


Bill,

 

I'm sending you my preliminary phase noise results.  As you recall, I
constructed a battery-powered 10 MHz oscillator by grabbing a junked
reference oscillator from an old HP signal generator and mounting it in a
box with two 9-volt batteries, a switch, and a BNC.  That allowed me to
bring it into work and use the Agilent ES5500 Phase Noise Measurement System
on it.  Then I brought it home as my poor-man's phase noise source.  Here's
the test results on the oscillator and the first look at the SDR-IQ:

 



                Phase noise of the battery-powered oscillator

 

 



Here's the same oscillator captured with the $400 SDR-IQ.  The SDR-IQ drifts
in relation to the device under test so the signal average is artificially
low.  It's really at 0db on the scale.  With the IF and RF gain set to their
lowest settings I think this lines up pretty well until the level drops down
to the SDR-IQ baseline noise level at about the 100 kHz point.  The 120 Hz
bump has to be coupling from the PC via the USB port where it gets its
power.  I was able to rid the SDR-14 of that by tossing the wall wart and
using a lab bench supply.  For now I'll just ignore this one.

 

What do you think?

 

Juan

 

-----Original Message-----
From: Bill Ress [mailto:bill at hsmicrowave.com] 
Sent: Tuesday, July 10, 2007 7:27 PM
To: Juan Rivera
Subject: 10 MHz Phase Noise

 

Hi Juan,

 

Really sorry you couldn't transmit this evening. I always enjoy your 

keen comments.

 

Thanks for the 10 MHz phase noise data. What is the model number for the 

HP oscillator? It's probably a version of the one I use.

 

Now  - - - - I'm really interested in what you read on your SDR. On the 

8566B you'll just be looking at its internal LO's phase noise floor but 

it will be very interesting to see what your SDR phase noise floor is. 

Your test results will be the key data point in my decision to buy one.

 

Again - much thanks for you fine work.

 

Regards...Bill - N6GHz

 

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