Date: Thu, 17 Jul 2008 15:28:56 -0400 From: "Jim.Ray" Subject: [IGSMAIL-5795]: Leica GRX1200GG Pro with external freq standard To: IGSMail Reply-to: jim.ray@noaa.gov Message-id: <487F9D78.1090304@noaa.gov> Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit User-Agent: Thunderbird 2.0.0.14 (Windows/20080421) Sender: owner-igsmail Precedence: bulk ****************************************************************************** IGS Electronic Mail 17 Jul 12:29:02 PDT 2008 Message Number 5795 ****************************************************************************** Author: Jim Ray While the Leica GRX1200GG Pro receiver is nominally equipped to accept an external frequency standard, it is not obvious how to get the receiver to actually slave the internal oscillator to the external signal. Within the IGS network, the following stations are reported to have such a configuration: DARW -- Rubidium WROC -- Rubidium WTZR -- H-maser However, in all cases the observed station clock performance is consistent with an internal crystal (steered to GPS time). This can be seen, for instance, in the plots posted at: https://goby.nrl.navy.mil/IGStime/filelisting.php?D1=IGST&D2=1486 for wk 1486. After a lengthy investigation working with personnel at the U.S. Naval Observatory and Leica, my colleague Ernie Marion has developed the following procedure, which seems to work in local tests. * Importantly, the Leica GRX1200GG Pro does not support control of the external oscillator directly via the web interface. This function must be addressed using the Leica "RX controller" device connected directly to the receiver, on site. If you do not have an RX controller, please contact Leica. * When using the RX controller, there is an option "user" in the external oscillator settings which must be used. See the image posted at: http://www.ngs.noaa.gov/igsacc/WWW/misc/leica-RX-controller.jpg * From here, you must enter the appropriate clock parameters. The necessary information should be known based on the technical specs for the external clock device in use. * To ensure that the external signal locks properly, switch from the 5 Mhz setting (if that is correct for the clock in use) to 10 Mhz. Let it save that setting, then watch to see that the receiver unlocks. Once it is unlocked, switch it back to 5 Mhz, and then it should lock again. * Then you can test this by removing the frequency reference cable. If it unlocks, that's good. Put the cable back, it should lock again. Then you are good to go! But it would be best to verify proper operation by later checking the IGS clock plots at the NRL website above. A similar procedure can be used if a 1 pps input signal is supplied (ordinarily only for time transfer operations). Just cycle the setting back and forth a few times to make sure of the correct setting. I very much appreciate the diligence of Ernie and his collaborators in resolving this issue.