From: Jon Clarke Date: 15 Jun 1999 13:43:25 Subject: [IGEXMail-0373] NPL time transfer 1pps retarded by 1.4 ns Laverty_John , Lowe_Andrew , Rougeaux_Benedicte , Shemar_Setnam , Whibberley_Peter X-Mailer: FTP Software Internet Mail 2.0 Mime-Version: 1.0 From: IGEXMAIL Service Subject: No 0373 : NPL time transfer 1pps retarded by 1.4 ns Date: Tue, 15 Jun 1999 12:15:04 +0100 Content-Type: text/plain; charset=US-ASCII; X-MAPIextension=".TXT" Content-Transfer-Encoding: 7bit Sender: owner-igexmail@ensg.ign.fr Precedence: bulk ****************************************************************************** IGEX Electronic Mail 15-Jun-1999 13:43:25 Message No 0373 ****************************************************************************** Author: Jon Clarke 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 -------------------------------------------------------------------- Mr Jon Clarke Time and Frequency, e-mail: jon.clarke@npl.co.uk 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. --------------------------------------------------------------------