# USRP N200 + SBX - problem receiving signal

**URL:** <https://www.ruby-forum.com/t/usrp-n200-sbx-problem-receiving-signal/213792>\
**Category:** GNU Radio\
**Created:** [November 11, 2011, 4:38pm UTC](https://www.ruby-forum.com/t/usrp-n200-sbx-problem-receiving-signal/213792 "2011-11-11T16:38:30Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\
**Post date:** [November 11, 2011, 4:38pm UTC](https://www.ruby-forum.com/t/usrp-n200-sbx-problem-receiving-signal/213792/1 "2011-11-11T16:38:30Z")

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Hello!

I’ve recenty got two USRP N200 with SBX daughter boards. I have managed  
to  
transmit simple sine signal with one USRP but I have problems receiving  
this signal. I dont see anything but noise in spectrum. I have measured  
signal that I am transmiting with spectrum analyzer and I see a spike in  
spectrum, so the transmiter must be working.

I am using UHD source and sink blocks as a “top layer” for USRP devices,  
and WX GUI FFT block for displaying spectrum. Sine frequency is 1kHz and  
I  
am samping with 200kHz. I have set the center frequency on 500MHz. I  
have  
tried both antenna ports on receiving device.

Is there some setting that I am missing?  
Thanks

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**Author:** ![urban\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/d6d6ee/32.png) [@urban\_k](https://www.ruby-forum.com/u/urban_k)\
**Post date:** [November 12, 2011, 3:31am UTC](https://www.ruby-forum.com/t/usrp-n200-sbx-problem-receiving-signal/213792/2 "2011-11-12T03:31:09Z")

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On 11/11/2011 07:37 AM, Urban K. wrote:

> Hello!
> 
> I’ve recenty got two USRP N200 with SBX daughter boards. I have managed to  
> transmit simple sine signal with one USRP but I have problems receiving

Does that mean you have confirmed transmission with a spectrum analyzer?

> this signal. I dont see anything but noise in spectrum. I have measured  
> signal that I am transmiting with spectrum analyzer and I see a spike in  
> spectrum, so the transmiter must be working.
> 
> I am using UHD source and sink blocks as a “top layer” for USRP devices,  
> and WX GUI FFT block for displaying spectrum. Sine frequency is 1kHz and I  
> am samping with 200kHz. I have set the center frequency on 500MHz. I have  
> tried both antenna ports on receiving device.
> 
> Is there some setting that I am missing?

Can you tell more information, or send your GRC flowgraph?  
What frequency, what digital amplitude, gains, etc…

If I can make some suggestions:

- Digital amplitude should be max magnitude 1.0, start with something  
way lower like 0.3.

- Use a larger sample rate, at least 1Msps. This can make it easier to  
debug.

- Did you pick the correct RX antenna?

- Have you tried increasing RX gain?

-Josh

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<div class="post-metadata">

**Author:** ![urban\_k](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/d6d6ee/32.png) [@urban\_k](https://www.ruby-forum.com/u/urban_k)\
**Post date:** [November 15, 2011, 9:20am UTC](https://www.ruby-forum.com/t/usrp-n200-sbx-problem-receiving-signal/213792/3 "2011-11-15T09:20:11Z")

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Hello!

Sorry for a bit late response. Regarding my problem

1. Yes I can see the signal that I am transmiting with spectrum analyzer

2. I tried all possible combinations for RX antenna

3.I have tried increasing RX gain

I attached my GRC flowgraph.