Re: [USRP-users] Single frequency interference for e310

[liu Jong via USRP-users]

Hi all,
Any suggestion is welcome.

2018-03-02 14:21 GMT+08:00 liu Jong :

> Hi all,
>When we set "master_clock_rate=25.6M" for Receiving and we found
> that there is a Single frequency interference in
> 76.8M(25.6X3),102.4M(25.6X4),153.6M and so on until above 1.5G.We changed
> the "master_clock_rate=16M",and we also found that there is a Single
> frequency interference in 80M(16X5),96M(16X6)and so on.The signal  power is
> larger than  noise about 5db.Is it the problem of the chip or the problem
> of USRP E310?
> thank you
> best regards
> Jon
>
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[USRP-users] Frequency tuning

[Javier Coronel (Expo Impex, S.L.) via USRP-users]

Hi Everybody!,

I have a B210 and I have done a MIMO frequency scanner to send and receive.
I always tune the same freq for both 2 Tx and  2 Rx.

Everything works very well even working at a Sampling Freq = 30MHz.

But I have checked that the functions set_tx_freq and set_rx_freq (that I
call 2 times each, one per antenna) are very slow.

I suppose that the reason is due to the B210 inners, but ¿is there any way
of tuning the same frequency on all 4 channels in a faster way?

To do the frequency scanning I have to tune the frequency continuously, so
this task is very time consuming.

Thank you vey much!

Best Regards,

Javier Coronel
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Re: [USRP-users] Transmitting and receiving on the same frequency with USRP B200

[Gilad Beeri (ApolloShield) via USRP-users]

* When you say a max gain of 89 dB, that is the gain you set in GNU Radio
on the USRP block right?
Yes (USRP Sink, not Source).

* With a 30dB attenuator, regardless of what I set the gain to on either
the rx/tx blocks in GNU Radio, and regardless of how far apart I position
the antennas I won't be able to damage the rx side will I?
Those are back-of-the-envelope calculations which assume max output power
of 30 dB, far-field positioning, and USRP B2xx as the receiver with 0 dBm
max input power (most daughterboards of N and X series have lower max input
power). It sounds like you're mostly experimenting and don't really care
about dynamic range and received power. In that case, why don't you put 60
dB attenuation? It's way more than enough.
Oh, you should also take into account the antenna gain, if they are both
simple omnidirectional, add the tx and rx antenna gain to the calculated
output power to get a more accurate measurement (60 dB should cover you
here if you use normal antennas).

* One thing I'm wondering also is how you calculated the dBm value for 49
dB tx gain?
I assumed 89 dB tx gain outputs ~ 15 dBm. Reduced 40 dB from the tx gain
and got 49 dB tx gain, thus reduced 40 dB from the output power and got ~
-25 dBm (15 - 40).


The best thing for you to do is to take the parameters requested in the
FSPL calculator, fill them in, and understand better the RF conditions of
your experiment.

On Sun, Mar 4, 2018 at 2:29 PM Christopher Richardson <
chrisrichardso...@gmail.com> wrote:

> Thanks a lot for your reply, lots of very useful information!
>
> A few questions:
>
> * When you say a max gain of 89 dB, that is the gain you set in GNU Radio
> on the USRP block right?
>
> * With a 30dB attenuator, regardless of what I set the gain to on either
> the rx/tx blocks in GNU Radio, and regardless of how far apart I position
> the antennas I won't be able to damage the rx side will I?
>
> * One thing I'm wondering also is how you calculated the dBm value for 49
> dB tx gain?
>
> Cheers
> Chris
>
>
> On Sun, Mar 4, 2018 at 6:00 AM, Gilad Beeri (ApolloShield) <
> gi...@apolloshield.com> wrote:
>
>> B200 has a max output power of ~ 15 dBm (give or take) in max gain (89
>> dB), depending on the frequency, and a max input power of 0 dBm. To be on
>> the safe side, you can and should take a 10 dB backoff, so for the sake of
>> discussion, assume the max input power is -10 dBm.
>>
>> You can use the Free Space Path Loss formula (calculator:
>> https://www.pasternack.com/t-calculator-fspl.aspx) to get a sense (the
>> formula is for the free space) of how much power you "lose" by using a
>> wireless channel, the results depend on your choice of frequency and
>> distance between antennas. You need to make sure the antennas are "far"
>> enough to be on the far field of each other.
>>
>> You can also take into account the attenuation the SMA cables add on both
>> sides, or, to save you all of the trouble,
>> you can just transmit with a gain low enough such that the transmitted
>> signal is weaker than the max input power (i.e., if 89 dB tx gain is ~ 15
>> dBm, then 49 dB tx gain is ~ -25 dBm, so you're good), and/or you can put a
>> 30 dB attenuator either in the tx or rx port, that way you'll know that
>> even if you make a software mistake, you're on the safe side.
>>
>> On Sun, Mar 4, 2018 at 3:38 AM Christopher Richardson via USRP-users <
>> usrp-users@lists.ettus.com> wrote:
>>
>>> Hi,
>>>
>>> I'm just wondering if anyone could give me some advice, I'm using the
>>> USRP
>>> B200 with GNU Radio with a simple FM example to transmit and receive on
>>> the same frequency.
>>>
>>> I made use of telescopic whip antennas on the Tx port and another on the
>>> Rx port, I had the antennas tilted away from each other, but I've been
>>> informed this could still be a bad idea and could overload the receiver? (I
>>> had also played with different Rx/Tx gain values while testing this).
>>>
>>> I'm just hoping I haven't damaged anything.
>>>
>>> I'm planning on now getting 2x 3 metre SMA cables to separate the
>>> antennas by around 6 metres, does this seem sensible?
>>>
>>> Cheers
>>>
>>> Chris
>>> ___
>>> USRP-users mailing list
>>> USRP-users@lists.ettus.com
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>
>>
>
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Re: [USRP-users] Transmitting and receiving on the same frequency with USRP B200

[Christopher Richardson via USRP-users]

Thanks a lot for your reply, lots of very useful information!

A few questions:

* When you say a max gain of 89 dB, that is the gain you set in GNU Radio
on the USRP block right?

* With a 30dB attenuator, regardless of what I set the gain to on either
the rx/tx blocks in GNU Radio, and regardless of how far apart I position
the antennas I won't be able to damage the rx side will I?

* One thing I'm wondering also is how you calculated the dBm value for 49
dB tx gain?

Cheers
Chris

On Sun, Mar 4, 2018 at 6:00 AM, Gilad Beeri (ApolloShield) <
gi...@apolloshield.com> wrote:

> B200 has a max output power of ~ 15 dBm (give or take) in max gain (89
> dB), depending on the frequency, and a max input power of 0 dBm. To be on
> the safe side, you can and should take a 10 dB backoff, so for the sake of
> discussion, assume the max input power is -10 dBm.
>
> You can use the Free Space Path Loss formula (calculator: https://www.
> pasternack.com/t-calculator-fspl.aspx) to get a sense (the formula is for
> the free space) of how much power you "lose" by using a wireless channel,
> the results depend on your choice of frequency and distance between
> antennas. You need to make sure the antennas are "far" enough to be on the
> far field of each other.
>
> You can also take into account the attenuation the SMA cables add on both
> sides, or, to save you all of the trouble,
> you can just transmit with a gain low enough such that the transmitted
> signal is weaker than the max input power (i.e., if 89 dB tx gain is ~ 15
> dBm, then 49 dB tx gain is ~ -25 dBm, so you're good), and/or you can put a
> 30 dB attenuator either in the tx or rx port, that way you'll know that
> even if you make a software mistake, you're on the safe side.
>
> On Sun, Mar 4, 2018 at 3:38 AM Christopher Richardson via USRP-users <
> usrp-users@lists.ettus.com> wrote:
>
>> Hi,
>>
>> I'm just wondering if anyone could give me some advice, I'm using the USRP
>> B200 with GNU Radio with a simple FM example to transmit and receive on
>> the same frequency.
>>
>> I made use of telescopic whip antennas on the Tx port and another on the
>> Rx port, I had the antennas tilted away from each other, but I've been
>> informed this could still be a bad idea and could overload the receiver? (I
>> had also played with different Rx/Tx gain values while testing this).
>>
>> I'm just hoping I haven't damaged anything.
>>
>> I'm planning on now getting 2x 3 metre SMA cables to separate the
>> antennas by around 6 metres, does this seem sensible?
>>
>> Cheers
>>
>> Chris
>> ___
>> USRP-users mailing list
>> USRP-users@lists.ettus.com
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>
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