Hello,

I did a few more tests to check the BS-11 clock accuracy. I took a phone which is registered to an official network and tried if I can see the BS-11 test network doing a manual network search.

As long as the BS-11 oscillator is not locked to the E1 clock, I can reliable find the test network.

After the BS-11 oscillator has locked to the E1-clock, the test network is only found every now and then. Here with my BS-11 it takes about 5 minutes till the oscillator is locked, the attribute is NM_ATT_BS11_CCLK_ACCURACY, "0" means "high accuracy" (locked), "1" means "medium accuracy" (free running), "2" most certainly "low accuracy" (not yet warmed up, I have not verified this value).

Most certainly the BS-11 oscillator is better than the oscillator of the E1-card, however I don't know if the calibration is still OK on all BS-11 units. I have not yet found an easy way to measure the BS-11 clock (without opening the case), the RF signal is always modulated and I don't have the equippment to measure the frequency of the modulated and pulsed RF signal in an accurate way. So this measurement has to wait.

What you can try is to disconnect the E1 line for about 30 seconds, this should be enough so that the Abis Link goes down. If you reconnect, I assume it takes a similar time to lock the oscillator like it did here. So you have a few minutes to start OpenBSC and check if you can find the test network.

If this works for most units, a possible workaround is to use the RX clock for TX on the HFC-E1 card instead of its own oscillator (this way the BS-11 oscillator determines the E1 clock). I tried that here already (on Windows), and it seems to work. However I don't know if mISDN can be configured this way or if it requires a small patch.

Best regards, Dieter