BS-11 clock accuracy

Hello, I think I finally found a way to measure the frequency of the BS-11 in a reliable way. My BS-11 is accurate to within 0.1 ppm if the oscillator is set to "Standalone Mode". If the oscillator is locked to the E1 clock of the HFC-E1 card and the HFC-E1 card is generating the clock, the frequency of the BS-11 drifts more than +/-1 ppm in about one minute. I did just a short test, but this results fits to the previous observations (remember, an old Nokia phone was not able to see the official networks and the test network at the same time if the frequency of the test network is off by more than 1 ppm). Of course I don't know how good the calibration of the other BS-11 units is, but setting the oscillator to "Standalone Mode" surely is better than using the HFC-E1 card for synchronisation (if the HFC-E1 card is not synchronized to the official ISDN network clock as Andreas suggested). Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de