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

Andrey Sviyazov andreysviyaz at gmail.com
Fri Aug 2 16:54:27 UTC 2013


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
>
>
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