Subject: [IGEXMail-0373] NPL time transfer 1pps retarded by 1.4 ns
From: Jon Clarke <[email-masked]>
Date: 15 Jun 1999 13:43:25

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Subject: No 0373 : NPL time transfer 1pps retarded by 1.4 ns
Date: Tue, 15 Jun 1999 12:15:04 +0100
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IGEX Electronic Mail    15-Jun-1999 13:43:25                   Message No 0373
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Author: Jon Clarke <[email-masked]>
Subject: NPL time transfer 1pps retarded by 1.4 ns

Dear Colleagues,

[apologies to those receiving this twice]

at 10:39 UTC the frequency distribution amplifier (id 183, HP 5087A) at 
the start of our standard signal distribution chain in our time 
transfer laboratory was exchanged. The new dist. amp. is id 106, Rapco 
type 809/A serial # 809A1/3287. 

It is hoped that this will reduce the short term interfering signal 
(approx. 12 min. period, 30ps amplitude) that has been visible on our 
geodetic GPS results for some time. 

According to our time interval data logging (TIDL) system, this has 
retarded the reference 1pps for NPLB (Ashtech Z12T), NPLC (R100), the 
Satre TWSTFT modem and the Mitrex TWTSFT modem by (1.4 +/- 0.1) ns. 

This measurement is consistent with delay measurements on the amps 
themselves, which indicate that the delay through the amps (old-new) 
are different by +101.389 ns, with 100ns of the difference being 
removed by retarding our time scale generator (id 180) by its minimum 
resolution of 0.1 microseconds.

Regards,
Jon Clarke

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Mr Jon Clarke                                    Time and Frequency,
e-mail: [email-masked]              Centre for Time Metrology,
tel: +44 (0) 181 943 6548              National Physical Laboratory,
fax: +44 (0) 181 943 7138    Queens Road, Teddington, TW11 0LW, U.K.
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