BS-11 runs, but no Network on my Mobile

[Dieter Spaar]

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
-- 
Dieter Spaar, Germany                           spaar at mirider.augusta.de