Abstract

Experiences with Timekeeping

Leszek Benedyktowicz
Presented by A. Wrembel

Ein Bericht über die Verbesserung der Zeitbestimmung von Bedeckungs-Phänomen und die in Polen während der letzten drei Jahre gesammelten Erfahrungen mit Zeitsignalen von Radiostationen, der Zeitverzögerung durch DCF-Module und der Zeiteinblendung in Videoaufnahmen.

During last ESOP meetings, there were presented some reports on timekeeping and methods improving its quality in purpose to record occultational events properly. This report is a continuation of this subject and contains experiences obtained in Poland in the period of last 3 years.

Introduced in 1990, the system basing on the DCF-77 radio-clocks became to be a standard for all of the observers associated in the Section of Observations of Positions and Occultations. Moreover, those signals are used as the time-basis by many institutions, for instance by aviation, commercial broadcasting, etc.

Nowadays, it is possible to receive time-signals from other stations, too, however, most of them require special receivers, not accessible for typical observers. The only regular broadcasting that emits its precise radio-signals quite regularly is the Polish Radio I. However, its signals are not so frequent as previously (nominally, every hours) and in addition, the signals often are being emitted simultaneously with the common program (music, talking, etc.). One of the worse thing we discovered is that some of the small local commercial radio broadcastings emitted their time-signals as re-transmitted ones, or they re-transmitted the program of Polish Radio I. In such situations, the delay is about 0.5 sec or more and it seriously affects the possible timing of events. Moreover, such errors have been found in observation reports but thanks to the intensive consultations, they were corrected in time. Nevertheless, the risk that the wrong timekeeping could be used by an unfamiliar observer is still remarkable.

Beginning from 1985, we can observe the ending of emission by many former stations. Old "demobilized" by army receivers allowed obtaining clear and strong time-signals from many stations in the world. Unfortunately, many of them cannot be readable from years. Using today's communication receivers, one can clearly receive in Poland time-signals from four stations : MSF Rugby, HGB Prangins, DCF77 and RWM Moscow. Even if all of them are not used by a common observer regularly, their signals are the basis used for control new purchased DCF modules. Each new module is checked whether its electronic improving and developing (i.e. installation of amplifiers, sound, etc.) do not cause disturbances and delays of time-signals. As it was said during our last meetings, almost all of re-developed or re-built DCF modules became to be late in relation to the original radio-signals. The delay amounts up to 0.06 sec. and depends on the example. Each observer who offers his purchased module for developing, receives the information on its delay as well as the short manual. The delay can be determined by comparison with the undelayed, original signals given by the bigger communication receivers and with the use of a special PC software and connector-interface, supplied by Janusz Wiland.

Recently, new DCF77 modules appeared on our market : "DCF Empfaengerplatine" and "Modul WT100", whereas the old "DCF77 Funk-Uhrmodell"-devices are not accessible more. The new receivers are less sensitive to disturbances but they require different adaptation for our goals. They are also used as the basic time-source for inserters co-operating with CCD cameras and for starting stopwatches automatically.

The co-operation of the DCF receivers with the inserters requires knowledge of the systematic delay, because we use some video-recorders with the frame frequency of 0.02 sec. Next, the elimination of all disturbances caused by the monitor and video-recorder is absolutely necessary. The DCF signal is not very strong in some cases in Poland and the setting of the inserter display is impossible in unfavourable conditions. Earthing the recorder and eliminating the unnecessary or improperly made cable connections guarantees the success in most cases.

The author makes all the necessary adaptations needed for observers of our Section.

Leszek Benedyktowicz, Polish Association of Amateur Astronomers (PAAS)
Address: ul. Ks. Józefa 355/13, Cracow 30-243, Poland E-Mail: ptma@oa.uj.edu.pl
Telephone:+48 12 6136571

Artur Wrembel, Filharmonia, ul. Libelta 16, Bydgoszcz 85-080, Poland,
E-Mail: krzgrzel@friko2.onet.pl Telephone: +48 52 604229301

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