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

[Bob Camp]

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> 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] 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> 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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