The Difference of Signal Strength From Two Channels on The Same Board is Big

Alexander Chemeris alexander.chemeris at gmail.com
Mon Aug 5 10:30:33 UTC 2013


Андрей, напиши ему свой адрес?
Меня в копию поставь.


On Sat, Aug 3, 2013 at 6:48 AM, jiangwy <wyjiang at ljshuoda.com> wrote:

> **
> Hi Andrey Sviyazov.
>
> I have tried the kal program on both boards, the output are:
>
>  The following commands are executed on the normal board
> ./kal -s GSM900 -v -R A:0
> kal: Scanning for GSM-900 base stations.
>
> channel detect threshold: 19506.878626
>
>         chan: 11 (937.2MHz - 13.389kHz) power: 53673.23
>
>         chan: 14 (937.8MHz +   4Hz)     power: 64031.10
>
>         chan: 16 (938.2MHz +  30Hz)     power: 37823.70
>
>         chan: 43 (943.6MHz +   2Hz)     power: 77249.29
>
>         chan: 50 (945.0MHz -  24Hz)     power: 29420.52
>
> ./kal -s GSM900 -v -R B:0
> kal: Scanning for GSM-900 base stations.
>
> channel detect threshold: 28406.616263
>
>         chan: 11 (937.2MHz - 6.120kHz)  power: 53776.77
>
>         chan: 14 (937.8MHz -  59Hz)     power: 76683.83
>
>         chan: 16 (938.2MHz + 28.945kHz) power: 46724.84
>
>         chan: 43 (943.6MHz + 38.130kHz) power: 65350.20
>         chan: 50 (945.0MHz -  21Hz)     power: 29930.09
>
> The following commands are executed on another board seeming to be abnormal
> ./kal -s GSM900 -v -R A:0
> kal: Scanning for GSM-900 base stations.
>
> channel detect threshold: 4486.504362
>
>         chan: 5 (936.0MHz -  15Hz)      power: 6734.70
>
>         chan: 12 (937.4MHz +  50Hz)     power: 9339.20
>         chan: 83 (951.6MHz -  13Hz)     power: 6462.91
>
> ./kal -s GSM900 -v -R B:0
> kal: Scanning for GSM-900 base stations.
>
> channel detect threshold: 27671.315417
>
>         chan: 5 (936.0MHz +  24Hz)      power: 29673.93
>
>         chan: 12 (937.4MHz +  40Hz)     power: 69096.60
>
>         chan: 83 (951.6MHz -   4Hz)     power: 46394.73
>
> ./kal -c 1004 -R A:0
> kal: Calculating clock frequency offset.
> Using E-GSM-900 channel 1004 (931.0MHz)
> average         [min, max]      (range, stddev)
> +   2Hz         [-80, 79]       (159, 44.543312)
> overruns: 0
> not found: 34
>
> ./kal -c 1004 -R B:0
> kal: Calculating clock frequency offset.
> Using E-GSM-900 channel 1004 (931.0MHz)
> average         [min, max]      (range, stddev)
> +   1Hz         [-13, 19]       (32, 8.658517)
> overruns: 0
> not found: 0
>
> Best Regards.
>
> ------------------------------
> jiangwy
>
>  *From:* Andrey Sviyazov <andreysviyaz at gmail.com>
> *Date:* 2013-08-03 00:54
> *To:* wyjiang <wyjiang at ljshuoda.com>
> *CC:* UmTRX <umtrx at lists.osmocom.org>; Alexander Chemeris<alexander.chemeris at gmail.com>
> *Subject:* Re: Re: The Difference of Signal Strength From Two Channels on
> The Same Board is Big
>  Hi Jiang Wenyi.
>
>  Please double check that both UmTRX's runs with the same FPGA images
> (and firmware).
> If absolutely the same then seems one board is broken.
> Please double check it also by some other tests to be sure before send to
> us for repair.
>
>  Best regards,
> Andrey Sviyazov.
>
>
> 2013/8/2 jiangwy <wyjiang at ljshuoda.com>
>
>> **
>> I try another UmTRX board, and it's OK. The difference from the channel 0
>> and 1 is very small.
>>
>> ------------------------------
>> jiangwy
>>
>>  *From:* Alexander Chemeris <alexander.chemeris at gmail.com>
>> *Date:* 2013-08-02 17:30
>> *To:* wyjiang <wyjiang at ljshuoda.com>
>> *CC:* UmTRX <umtrx at lists.osmocom.org>
>> *Subject:* Re: Re: The Difference of Signal Strength From Two Channels
>> on The Same Board is Big
>>   Ok.
>>
>> Also check that a correct input is selected on both chips
>> (--lms-get-rx-lna option).
>>
>>
>> Then, could you check whether this is consistent among both UmTRX you have?
>>
>> On Fri, Aug 2, 2013 at 12:55 PM, jiangwy <wyjiang at ljshuoda.com> wrote:
>> > I use the following command
>> >
>> > ./umtrx_lms.py --lms {1,2} --lms-get-rx-vga2-gain
>> >
>> > the outputs are all the same ( 15 ).
>> >
>> > ________________________________
>> > jiangwy
>> >
>> > From: Alexander Chemeris
>> > Date: 2013-08-02 16:20
>> > To: wyjiang
>> > CC: UmTRX
>>
>> > Subject: Re: The Difference of Signal Strength From Two Channels on The Same
>> > Board is Big
>> > Hi Jiang,
>> >
>> > Are you sure you're setting Rx gain properly for both channels?
>> > I recommend you to use umtrx_lms.py script from this repository to
>> > check Rx LNA and Rx VGA settings for both LMS chips:
>> > https://github.com/fairwaves/umtrx_scripts
>> >
>> > On Fri, Aug 2, 2013 at 12:09 PM, jiangwy <wyjiang at ljshuoda.com> wrote:
>> >> Hi Alexander Chemeris,
>> >>
>>
>> >> According to rx_multi_samples , I write a program to receive samples from
>> >> two channels on the same board.
>> >> The program receive samples from 2 channels and calculate the signal
>> >> strength respectively. The signal is from a BTS arround.
>> >> I find the difference of signal strength is very big, about 20dB, and
>> >> channel 1 is bigger than channel 0.
>> >> I  exchange the antenna and feeder of the them, but the result is same.
>> >> I think there is some problem, but I cann't find it.
>> >> Would you please give me some sugguestion?
>> >>
>> >> Best Regards.
>> >>
>> >> ________________________________
>> >> Jiang Wenyi
>> >
>> >
>> >
>> > --
>> > Regards,
>> > Alexander Chemeris.
>> > CEO, Fairwaves LLC / ООО УмРадио
>> > http://fairwaves.ru
>> >
>>
>>
>>
>> --
>> Regards,
>> Alexander Chemeris.
>> CEO, Fairwaves LLC / ООО УмРадио
>> http://fairwaves.ru
>>
>>
>
>


-- 
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
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