From vicente@cay.oan.es Tue Oct 26 21:52:38 MET 1999 Received: from siva.cay.oan.es (siva.cay.oan.es [193.146.252.16]) by picasso.geod.uni-bonn.de with ESMTP (8.8.6 (PHNE_14041)/8.8.8) id VAA19477; Tue, 26 Oct 1999 21:52:25 +0200 (METDST) Received: from polifemo (vicente@polifemo [193.146.252.30]) by siva.cay.oan.es (8.9.3/8.9.1) with SMTP id VAA10368; Tue, 26 Oct 1999 21:51:18 +0200 (METDST) From: Pablo de Vicente Reply-To: vicente@cay.oan.es Organization: Observatorio Astronomico Nacional To: Brian Corey , tme@cygx3.usno.navy.mil (Marshall Eubanks) Subject: Little test at Yebes with distributor Date: Tue, 26 Oct 1999 21:46:57 +0200 X-Mailer: KMail [version 1.0.28] Content-Type: Multipart/Mixed; boundary="Boundary-=_nWlrBbmQBhCDarzOwKkYHIDdqSCD" Cc: petrov@picasso.geod.uni-bonn.de, aen@haystack.mit.edu, baa@casa.usno.navy.mil, dgg@aquila.gsfc.nasa.gov, hase@wettzell.ifag.de, mueskens@mpifr-bonn.mpg.de, nothnage@picasso.geod.uni-bonn.de, sorgente@hp138.mpifr-bonn.mpg.de, tme@cygx3.usno.navy.mil, vicente@cay.oan.es, vlbi@oan.es, weh@ivscc.gsfc.nasa.gov References: <199910252025.QAA21954@dopey.haystack.edu> In-Reply-To: <199910252025.QAA21954@dopey.haystack.edu> MIME-Version: 1.0 Message-Id: <99102621511800.18208@polifemo> Status: R --Boundary-=_nWlrBbmQBhCDarzOwKkYHIDdqSCD Content-Type: text/plain Content-Transfer-Encoding: 8bit Following Brian's advise we have used the phase cal ground unit to measure the delay between two signals of 5 MHz. For that we have unplugged the bridges in the rear of the module which pass the ref and signal 5 MHz from the demultiplexer module to the phase comparator. Our reference signal was 5 MHz coming from the maser through the 5 MHz distributor of the VLBA DAR that we assume to be clean. The signal signal was 5 MHz coming from the auxiliary 5 MHz distributor which we have tagged as faulty due to its dependence on temperature. We have switched on and off the air conditioning and redirected it towards the auxiliary distributor. We have placed a thermometer probe on the top of the distributor and measured the temperature in Kelvin. The register of the delay has been done with an HP counter and the FS computer while the values from the thermometer were taken from another PC sincronized within 2 seconds with the FS time. The following is a jpeg file containing the data. You will notice I miss some data from the counter due to some failures reading the HPIB port with the FS. If we assume that both data sets are completely correlated the sensitivity is 8 ps/C, very close to the nominal value of the distributor. To convert the units from the counter you have to divide them by 2.5e5. A change of 0.0111-0.109 of the counter = 1e-9 s is produced by a change of temperature of 12.4 K. Does this sensitivity explain the values seen at the correlator?. Pablo. -- ________________________________________________________ Pablo de Vicente (vicente@oan.es), http://www.oan.es, OAN Spain