[time-nuts] Why a 10MHz sinewave output?

Joseph M Gwinn gwinn at raytheon.com
Mon Feb 6 18:59:14 UTC 2012

As mentioned below, the propagation speed of the various harmonics varies.
What also varies is the temperature coefficient of propagation speed.
This, taken with imperfect impedance matches, yields complicated variation
of zero-crossing times with temperature.

The tempcos are particularly large below about 60 MHz, so operation at 100
MHz is helpful.  The ratio of tempcos is about 2:1.

Joe Gwinn

Ref:  “Environmental Effects in Mixers and Frequency Distribution Systems”,
L.M.Nelson and F.L.Walls, NIST, 1992 IEEE Frequency Control Symposium,
pages 831-837.

time-nuts-bounces at febo.com wrote on 02/06/2012 09:37:59 AM:

> From: Jim Lux <jimlux at earthlink.net>
> To: time-nuts at febo.com
> Date: 02/06/2012 09:38 AM
> Subject: Re: [time-nuts] Why a 10MHz sinewave output?
> Sent by: time-nuts-bounces at febo.com
> On 2/6/12 6:14 AM, paul swed wrote:
> > Indeed the long cable runs are tough. Though today we have differential
> > cable drivers that do quite well to the Ghz range. But
> certainly back in
> > the dark ages the sine wave was a very reasonable way to go.
> > Regards
> > Paul
> >
> we may have GHz bandwidth drivers, but that doesn't solve the issue of
> frequency dependent propagation through a cable.  At lowish frequencies
> (<100 MHz) I'd suspect that the difference is more one of amplitude than
> phase, but still, it's something that has to be dealt with.
> One could just have a narrow band filter at the receiving end to pick up
> only the fundamental, but then, why not just send only the fundamental.
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