From Jim Mon Jul 27 12:43:17 1998 From: Jim (Jim) Date: Mon, 27 Jul 1998 12:43:17 PDT Subject: [IGSMAIL-1965] changes planned at USNO Message-ID: ****************************************************************************** IGS Electronic Mail Mon Jul 27 12:43:17 PDT 1998 Message Number 1965 ****************************************************************************** Author: Jim Ray Subject: changes planned at USNO In order to make the following configuration changes, data from the USNO receiver will be interrupted on Wednesday, 12 August: * The AOA TurboRogue SNR12 receiver will be moved to an environmentally controlled chamber within the USNO clock vault. (The receiver will not otherwise be changed). Within the chamber, the temperature is controlled to +/- 0.15 C and relative humidity to +/- 1%. * A new antenna cable will be installed: Antenna cable 24-APR-1997 to 12-AUG-1998: Belden RG-214/U -- 200 feet (60.96 m) length (mostly exposed to full sun running along rooftop of Bldg 52) specifications: Velocity factor 0.66 Capacitance 30.8 pf/foot Loss at 1200 MHz 9.0 db/100 foot Loss at 1500 MHz 10.1 db/100 foot Electrical Length Change versus Temperature: 3000 PPM over (-10 to 42 C range) or 58 PPM/C => 0.2 ps/m/C or 12 ps/C for 200 feet Antenna cable 12-AUG-1998 to present: Andrew FSJ1-50A (35422-33 phase stabilized) 1/4 inch Superflexible Foam Dielectric Heliax -- electrical length will be measured at the time of installation (mostly run in the ceiling of the 3rd floor of Bldg 52) specifications: Velocity factor 0.84 DC resistance 2 to 3 ohms per 1000 foot Capacitance 24.2 pF/foot Inductance .061 uH/foot Loss at 1250 MHz 6.77 db/100 foot Loss at 1500 MHz 7.47 db/100 foot Electrical Length Change versus Temperature: 400 PPM over (-40 to 30 C range) or 5.7 PPM/C => 0.02 ps/m/C or 1.2 ps/C for 200 feet * A new PC controller will be installed. An updated station log will be sent to the IGS Central Bureau. We apologize for the service disruption but are hopeful that the changes will improve the USNO clock stability and performance by greatly reducing the sensitivity to temperature changes. ========================================================================= Jim Ray e-mail: jimr at maia.usno.navy.mil U.S. Naval Observatory, EO Dept. phone : 202-762-1444 3450 Massachusetts Avenue, NW fax : 202-762-1563 Washington, DC 20392-5420 ========================================================================= [Mailed From: Jim Ray (USNO 202-762-1444) ]