[eagle] Re: 10 MHz Phase Noise

Bill Ress bill at hsmicrowave.com
Wed Jul 11 17:24:57 PDT 2007

Hi Juan,

Thanks for collecting the data. Now I'm flat amazed!!!

Assuming, as you say, that the signal is referenced to 0 dBm in the 
SDR-IQ then it is essentially repeating the data at 10 Hz and 100Hz that 
you got for the 10 MHz oscillator on the HP ES5500. That is really 
super! I'm putting an SDR-IQ in the budget. Using clean heterodyne 
sources, the SDR-IQ will make a great back end for a VHF-microwave phase 
noise test set (unless I'm missing something).

I don't remember the schematic for the SDR-IQ but I think the reference 
oscillator is just an ordinary crystal oscillator - right? If so that 
accounts for the center frequency drift.

Do you have a HP part number for the 10 MHz oscillator?

Regards...Bill - N6GHz

Juan Rivera wrote:
> 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

More information about the Eagle mailing list