[time-nuts] Advice on 10 MHz isolation/distribution (Clay)

[Bob Camp]

Hi

Have you looked into any actual data on small rf transformers under
vibration at 10 MHz? 

A change of a nH isn't the same thing at 10 MHz as at 6.3 GHz. An air core
coil in the signal path at 6G would indeed be an issue. A circulator likely
would not be. An RF transformer at 10 MHz has a lot more in common with the
6GHz circulator than with the 6GHz air core coil. 

The phase noise of your reference is going to head up by your +56 db. As
long as the transformer's impact is well below the reference, it will not
show up in the output signal.

I would bet you an order of fries at the local MacDonald's that the single
ended transmission of the signal will pick up far more noise than anything a
properly constructed rf transformer will do at 10 MHz. 

Noise at the load is a problem, no matter how it gets there. Transmission
may not be inside your scope -yet. It's still an issue that directly impacts
what you are trying to do.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of life speed
Sent: Thursday, February 18, 2010 4:47 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution (Clay)

Message: 5
Date: Thu, 18 Feb 2010 11:11:18 -0800
From: Hal Murray <hmurray at megapathdsl.net>
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution
    (Clay)

> Thank you, but I require a circuit without transformers
> for reasons of vibration susceptibility.

Is the problem wires moving relative to eachother within the transformer or 
the whole transformer moving relative to the local magnetic field?

Does it help to pot things in epoxy or varnish or ...?

Years ago, when I took the lid off a small mini-circuits transformer it was 
just a few turns on a toroid.  Something like varnish would be easy to
apply.

Hal,

The problem is modulation of the reference signal via relative movement of
the transformer guts.  While I understand there are ways to 'harden'
magnetic devices, my application is far too sensitive to even consider a
magnetic approach given the availability of alternatives.  Any spurious
signals present on the 10 MHz reference will be increased by 56 dB by the
phase-locked loop.

Clay


      

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