[time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier?
magnus at rubidium.dyndns.org
Mon Jan 5 23:15:27 EST 2015
I was doing some phase noise measurements today at a friends place.
The Rapco 1804M was about -110 dBc/Hz at 10 kHz. It was 30 dB higher up
from the HP5065A, which was some 10 dB higher than the BVA. On the other
hand, when viewing the ADEV and TDEV, it became apparent that the Rapco
has around 1 ps RMS noise at 1 s, and few counters will be affected by
that noise. Just to put it in context.
So, one should at least ponder about where the noise contributions is
and what value it brings to go for a quieter distribution amp, and for
what in (additional) cost.
On 01/06/2015 01:59 AM, Bob Camp wrote:
> Any time you run into terms like “low noise” it pays to think about what that means to you and your system. A quick scan of the posts here over the years will show that different definitions of low noise do exist. The same is true of system requirements. An offset that matters to one may have no impact at all on another system.
> In some cases -155 dbc/Hz at 10KHz or 100 KHz is “low noise”. In other cases “low noise” is -180 dbc/Hz. In either case, *delivering* a clean signal without spurs and crud is far from simple. In many long cable run cases, the cost of fancy cables, high performance magnetics, and all the other “stuff” is more than the cost of simply locking up a quiet oscillator on the end of a “dirty” cable. I don’t think I’ve ever seen a setup that tries / needs to “distribute” < -170 dbc/Hz signals over anything bigger than a rack. I’ve seen *lots* of systems that regenerate those sort of signals many times over (= in many different boxes) to get around distributing them.
>> On Jan 5, 2015, at 2:15 PM, Tom Knox <actast at hotmail.com> wrote:
>> Happy New Years All! I have seen a number of discussions on various approaches to distribution amps discussed on Time-Nuts ranging from DYI to products intended for Video.
>> I thought I my weigh in with one point of interest; It seems like long term performance is pretty easy, but a low phase noise solution is quite a different story. Looking at the number of application specific products from MicroSemi/Symmetricom and other manufactures claimed and even more so real world specs vary a great deal so apparently it s not easy to just throw something together with great or even good close in phase noise. So depending on your labs direction in the future it may be worth researching and investing in an application specific distribution amp. I like the MicroSemi 4036B but there are a number of very good products out there on the surplus market selling for a small fraction of their original cost.
>> Thomas Knox
>>> From: bill.riches at verizon.net
>>> To: time-nuts at febo.com
>>> Date: Sun, 4 Jan 2015 08:29:34 -0500
>>> Subject: Re: [time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier?
>>> A cheap and dirty equivalent of a pass thru terminator that I use is a BNC t
>>> connector with a 52 ohm bnc terminator. I guess you could use a CATV 75 ohm
>>> F type with an adapter. Maybe that combination would produce too much
>>> Bill, WA2DVU
>>> Cape May
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