[time-nuts] Maser 0.7 nsec jumps solved

[Tom Van Baak]

Hi Jim,

Thanks much for the update. I can see how this was a pain to track down.

For those that don't remember the issue, the archive starts here:
https://www.febo.com/pipermail/time-nuts/2015-December/094904.html
And note that 1 / 0.704 ns = 1420 MHz, the frequency of a H-maser.

So it's either electrical or magnetic or seismic, yes? Does it happen every time the HVAC turns on/off? Can you run a high-resolution phase comparator during the event to find the time constant of the phase jump / cycle slip? 1 kHz sample rate should be more than enough. That may help narrow down which circuit is at fault.

/tvb

----- Original Message ----- 
From: "Jim Palfreyman" <jim77742 at gmail.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Saturday, May 21, 2016 6:58 PM
Subject: [time-nuts] Maser 0.7 nsec jumps solved


> Hi all,
> 
> Awhile back I posted about some mysterious 0.7 ns jumps in three different
> masers (of the same brand) at three different locations around Australia.
> 
> Well we think we've found the problem. All three locations also have
> in-room air conditioners of the same brand. These are used for cooling
> only. When these units turn on, we think they induce a magnetic field from
> the inrush current that briefly disrupts the maser. We don't think it's
> electrical because moving to another phase did not change things.
> 
> These air conditioners are all quite close to the masers. Typically a metre
> or 2 away.
> 
> Much was done to discover this, but the clincher was that when the weather
> cooled enough at the southern most location (Hobart), we turned off the air
> con (only heating was needed) and the problem vanished.
> 
> So there's a lesson here for all maser owners. The jump of 0.7 nsec is not
> much, but it's huge for VLBI and for time-nuts.
> 
> 
> Jim Palfreyman
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