Brilliant! \o/ Cheers, Domi
> 2020. okt. 27. dátummal, 1:28 időpontban Sipos Csaba <[email protected]> > írta: > > > It works! > > Long story short: the LimeSDR-Mini was off by 3.5kHz, and not the phone. Even > after 30 years, the phone is only off by 14Hz, what a performance. Made in > West Germany :-)) > > After the recalibration of the LimeSDR Mini, the phone successfully updated > the TA and went to normal idle state. Calls are also possible, SMS will be > tested when a capable phone arrives. All TA combinations were tested (1-15). > > Will create an updated patch for the country specific settings, now that it > is tested. > > The lesson is: trust but verify :-) Especially with cheap hardware. > > Regards, > Csaba > > Tomcsanyi, Domonkos <[email protected]> ezt írta (időpont: 2020. okt. 26., > H, 19:54): >> Hello Csaba, >> >> I am not sure if you know this, wanted to mention it: you could easily >> measure your SDR’s oscillator accuracy using the kalibrate tool. It uses >> nearby GSM BTSs if I am correct to give you a good estimation about how much >> off your oscillator is. >> I used to use it with rtl-sdr a lot, because those USB dongles are crazy off >> in terms off accuracy. >> Once you have an offset figured out for the current temperature I guess you >> could try to offset the frequency set by osmocom by that amount. Maybe even >> try to expose it as a variable if needed. >> Other solution would be using some kind of a GPSDO or similar 10 MHz input >> if the LineSDR supports it. >> >> Sorry again if this is known info, but wanted to chime in with some >> hopefully helpful bits. >> >> Cheers, >> Domi >> >> >>> 2020. okt. 26. dátummal, 16:08 időpontban Sipos Csaba >>> <[email protected]> írta: >>> >>> >>> Hi Ralph, >>> >>> I attached the patch for the country specific settings for Hungary, you can >>> apply it against "master" . TAs are not yet verified, but the phone goes >>> "green" with all TAs from 1 to 15. The RF part and country code are >>> verified. >>> >>> > One thing, maybe your MCR has drifted, due to ageing?! >>> >>> Well, that was my first impression too, as if you look at my picture ( >>> http://www.imagebam.com/image/d17e881357285965 ) you will see that the >>> center of the downlink and uplink transmissions are not exactly 10MHz >>> apart, they have a couple kHz drift. On the picture the two markers are >>> indicating the nominal frequency of the channel. As you can see the uplink >>> burst is actually closer to the nominal frequency, compared to the >>> downlink. It is not in the standard (or I was not able to find it, in >>> general the RF spec is not very detailed...), so I am not sure if the SDRs >>> downlink signal is off, and the phone is correct or the other way around. >>> Although it sure looks like a low layer fault, as the NMT network is not >>> even detecting is as bad or incorrect frames. >>> >>> I did a loopback test with a jumper between the TX and RX of the SDR and >>> that seemed to work (frame level and frame quality were 90+%). On the other >>> hand if the local oscillator would be off, the phone would not be able to >>> lock on the DL signal as well. I have no high precision counter at home, >>> but with a relatively primitive multimeter I was able to measure 12.7999MHz >>> on the 12.8MHz local oscillator. And both identical phones behave the same. >>> >>> The question is if I can somehow offset the uplink frequency on the SDR >>> side or via config/source modification to remove this couple kHz drift? >>> >>> If someone has seen a lot of these signals and can take a look at the image >>> above, would be lovely to hear if any of the signals are off. >>> >>> I will also get another more "modern" phone hopefully soon, so I can try >>> with that. >>> >>> Regards, >>> Csaba >>> >>> Ralph A. Schmid, dk5ras <[email protected]> ezt írta (időpont: 2020. okt. >>> 26., H, 15:33): >>>> Hi Chaba, >>>> >>>> >>>> >>>> I have a Nokia handheld phone from Hungary, I can try with your settings >>>> and let you know. >>>> >>>> >>>> >>>> Andreas seems to be difficult to reach these days, I found the same :/ >>>> >>>> >>>> With best regards >>>> >>>> >>>> Ralph. >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> From: OpenBSC [mailto:[email protected]] On Behalf Of >>>> Sipos Csaba >>>> Sent: Monday, October 26, 2020 3:16 PM >>>> To: [email protected] <[email protected]> >>>> Subject: Fwd: NMT-450 - partial success >>>> >>>> >>>> >>>> Hi, >>>> >>>> >>>> >>>> I know it is a bit off topic, but as osmocom-analog has no dedicated mail >>>> list and my every attempt to contact Andreas lead to silence, I thought >>>> this is the closest one to discuss it. >>>> >>>> >>>> >>>> I try to create an NMT-450 network with Motorola MCR4800XL phones, and a >>>> LimeSDR-mini. As the phones are locked to "Hungary" using a specific >>>> raster and a large gap in the middle, first I needed to dig out the >>>> details, find out the country code and create a patch so at least the >>>> phone is willing to lock onto the DS signal. I managed to do all that, so >>>> now the phone is actually able to decode the network and lock onto the >>>> signal. >>>> >>>> >>>> >>>> My issue is with the uplink: when the phone tries Traffic Area update (the >>>> phone's uplink transmission burts is clearly seen with a spectrum >>>> analyzer), the network side is not able to detect the uplink burst at all. >>>> Not even as bad, or incorrectly formatted frame. Andreas has a site which >>>> describes how to set up the uplink side and do some tests: >>>> >>>> >>>> >>>> http://osmocom-analog.eversberg.eu/docs/sdr.html >>>> >>>> >>>> >>>> I followed that guide and when the uplink burst from the phone arrives, >>>> the RX IQ constellation monitor indicates a correct burst with proper >>>> power (the burst is nicely round and in the green area). If I try to set >>>> up a call to the phone using the correct country code and phone number, >>>> the phone clearly responds to the paging request, as the 3 paging attempt >>>> generates 3 uplink bursts. Again, with no reception/decoding on the >>>> network side. Tried with two phones of the same type, the effect is the >>>> same. >>>> >>>> >>>> >>>> I have two questions: >>>> >>>> >>>> >>>> 1. Where to send patches for the osmocom-analog project? >>>> >>>> 2. Does anyone have an idea what can be wrong with my setup? >>>> >>>> >>>> >>>> One more thing I noticed: compared to the channel frequency used to set >>>> the NMT network up, the uplink is a couple kHz shifted: >>>> >>>> >>>> >>>> http://www.imagebam.com/image/d17e881357285965 >>>> >>>> >>>> >>>> As it can be seen, the uplink burst appears 3-4kHz left relative to the >>>> downlink signal. >>>> >>>> >>>> >>>> The network is started with the following command: >>>> >>>> nmt -k 239 -k 235 -Y HU,1 --limesdr-mini --sdr-rx-gain 20 >>>> >>>> >>>> >>>> Any and all help is appreciated. >>>> >>>> >>>> >>>> Regards, >>>> >>>> Csaba >>>> >>> >>> <0001-Add-country-specific-settings-for-Hungary.patch>
