[time-nuts] Low Additive Phase Noise 10 MHz Amps

Neil Schroeder gigneil at gmail.com
Mon Nov 24 01:35:56 EST 2014


My approach in progress is LVPECL driver from the master clock to a low
cost "clock cleaner" PLL with a low phase noise VCXO (mine are crysteks and
abracon depending on what I felt like at the moment).

Does that sort of approach match your requirement?  It isn't as low cost as
a dist amp but the results should theoretically be quite good. I'm not
instrumented to REALLY test the fine edges of performance but...



On Sunday, November 23, 2014, Bill <bill at hsmicrowave.com> wrote:

> Hi Bob,
>
> Thanks for your comments.
>
> The devices in my lab that can benefit from the low phase 10 MHz source
> are 1) the spectrum analyzer(s), 2) a  Comstron direct synthesizer, 3) the
> synthesized signal generators and the test source(s) used to drive
> microwave multipliers and signal sources. All these devices will see the 10
> MHz phase noise (improvements) within the narrowest PLL the devices use.
>
> After spending "bucks" for a low noise 10 MHz source, I can't afford to
> use one for each instrument. Besides it would hurt to go through the
> trouble of buying a low phase noise 10 MHz reference and lose it in a poor
> distribution amplifier(s). Also, the advantages of running all instruments
> from the same 10 MHz source are well known.
>
> So while I was hoping to short circuit some of the design/prototyping
> effort in the hopes someone on this thread had been there,  I'll just "hit
> the books" and do some prototyping and noise testing and see what I come up
> with.
>
> Regards...Bill
>
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com <javascript:;>] On
> Behalf Of Bob Camp
> Sent: Sunday, November 23, 2014 7:08 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps
>
> Hi
>
> While OCXO’s that have -170 dbc/ Hz specs are fairly common, they normally
> go deep inside a box of some sort. It’s a rare off the shelf device that
> takes in the output of a distribution amp *and* requires that sort of phase
> noise.
>
> What’s your target device(s)?
>
> Why do I ask? Well, a device that has a -170 dbc floor combined with a
> -170 dbc oscillator will give you -167. A device with a -200 dbc floor will
> still “degrade” a -170 dbc oscillator. That’s a fairly big change in
> circuit complexity (and cost) for a 2.9 something db improvement. The list
> of devices that might make it worth spending (say) a few hundred dollars a
> channel versus under a buck a channel is pretty short. That may put a bound
> on this.
>
> One example may help: If you are running phase noise testing, forget about
> multi channel distribution amps. They will add a ground loop(s) / pickup
> loop(s) that you will be fighting forever and ever. Do that sort of stuff
> straight off the oscillator. There is no rational amount of money (ummm ….
> errrr … how much do you have?) you can spend to get around this. A second
> (or eighth) oscillator is cheaper than even some of the simple approaches
> that don’t work very well. The type of OCXO you are talking about is a <
> $50 item on eBay.
>
> Bob
>
>
> > On Nov 23, 2014, at 9:17 PM, Bill <bill at hsmicrowave.com <javascript:;>>
> wrote:
> >
> > Thanks to all for the response but the distribution amp additive noise
> can be a real problem since the 10 MHz to be distributed is -170 dBC/Hz at
> 10 KHz and needs to be preserved if at all possible.
> >
> > BTW, the Ettus Octobox doesn't have a spec for additive phase noise, so
> that's out.
> >
> > Again thanks...Bill
> >
> > -----Original Message-----
> > From: time-nuts [mailto:time-nuts-bounces at febo.com <javascript:;>] On
> Behalf Of Bob
> > Camp
> > Sent: Sunday, November 23, 2014 1:09 PM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps
> >
> > Hi
> >
> > For any “real world” source being distributed, simple high speed CMOS
> buffers will not add enough noise to matter at 10 MHz. That of course also
> assumes that the target gear is the normal bunch of instruments that we all
> play with.
> >
> > Bob
> >
> >> On Nov 23, 2014, at 11:47 AM, Bill <bill at hsmicrowave.com <javascript:;>>
> wrote:
> >>
> >> What's the latest opinion (data) on available low additive phase
> >> noise
> >> 10 MHz amplifiers for 10 MHz distribution?
> >>
> >>
> >>
> >> Regards and thanks.Bill
> >>
> >>
> >>
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