I have made an experimental secondary phase noise standard, as F.Walls

would call it. In the end, it's inspired by his paper.

There is not much to it. There is a Mini Circuits PSC2-1 splitter that is

fed from an oscillator or other source. The splitter divides it into a

clean output that goes to another SMA.

The other half is to be dirtyfied. It is fed into another PSC2-1 that is

used as a combiner. Its output goes to the signal source analyzer via

a third SMA.

The dirt input is either  a 4th SMA or a noise generator. That is switched

by reed relays. The noise generator consists of a 60 Ohm resistor and

currently 2 LMH6702 stages for +20 and +40 dB. I'm not sure if the

60R really defines the level, but the gain is at least flat from AF

to > 100 MHz. If not yet, it can be made so. I have already a

solid step attenuator so I can get rid of those reed relays.

I checked it this evening with my FE405 osc I bought earlier this year

and that has enjoyed a good month of continuous running by now.

I observed

1. that the FEI delivers only 3.5 dBm

2. that there are lots of birdies far out.    Is that normal, maybe
   from the DDS?

The addition of the noise reference lines seems to work properly.

oscillator:

<
https://www.flickr.com/photos/137684711@N07/30824608092/in/album-72157662535945536/

low calibration line:

<
https://www.flickr.com/photos/137684711@N07/30824607162/in/album-72157662535945536/

high calibration line:

<
https://www.flickr.com/photos/137684711@N07/30824607552/in/album-72157662535945536/

Later this evening I'll add the pic of the tin box. I need a USB cable...

:-)  Gerhard

Hi

Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS spurs come
straight through. Since the FE-405 compensates for all sorts of things, the DDS moves
around a lot. Even a one bit change on a DDS will move spurs around. With an ever changing
DDS, you have an ever changing forest of “stuff” on the output.

Not the best thing for a “standard” …..

Bob

Am 12.11.2016 um 23:52 schrieb Bob Camp:

I would not expect a lot of dynamics after a month of cont. power up.
And the spurs
do not move and they don't average away, at least not within my limits
of boredom.

The PLL bandwidth seems to be 50 Hz, so the forest from 100KHz to 5MHz is
far out. That seems somewhat weird and raised doubt together
with the power level being out of spec.

I've tried to kill 2 birds with one stone. The FE405 had collected dust for
months and still was mostly untested.

The oscillator is not part of the "standard"; I could have used a BVA or
a maser by just plugging in. I just needed a centre frequency with a
few dBm for the E5052B to lock on.

All I want is some known phase noise reference reference lines
for my private phase detector experiments. Recalibating the
phase detector by modulating oscillators on different frequencies
is no fun if you change the Schottkies every 2 minutes.

regards, Gerhard

Hi

The spurs you need to watch are under 50Hz. They are the ones from the DDS. The higher
stuff is from the microprocessor.

Bob