# Simple Tx/Rx setup

**URL:** <https://www.ruby-forum.com/t/simple-tx-rx-setup/237295>\
**Category:** GNU Radio\
**Created:** [November 4, 2013, 3:56pm UTC](https://www.ruby-forum.com/t/simple-tx-rx-setup/237295 "2013-11-04T15:56:31Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [November 4, 2013, 3:56pm UTC](https://www.ruby-forum.com/t/simple-tx-rx-setup/237295/1 "2013-11-04T15:56:31Z")

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Hello folks,

I am attempting to transmit a bit stream from one bladeRF to another  
bladeRF  
using an SMA cable from the Tx output to the Rx input of the other. For  
simplicity’s sake, I’m transmitting a finite bit stream of 1’s (not  
ASCII  
1’s), and setting the File Source to not repeat itself.

I started by modifying …/gr\_digital/examples/demod/dpsk\_loopback.grc to  
a  
Tx/Rx setup as follows. I am trying to get the bladeRFs communicating at  
‘baseband’ before moving on to OFDM transmission.

Tx.grc: [tx.grc - Pastebin.com](http://pastebin.com/HFFtXuHW)  
Rx.grc: [\<?xml version='1.0' encoding='ASCII'?\>\<flow\_graph\> \<timestamp\>Mon Nov 4 14 - Pastebin.com](http://pastebin.com/hFRTZsm3)

I’ve noticed, when using a hex editor to compare the files at each  
respective stage, namely that iq\_in does not match iq\_out.

On that note, are there any simple examples (.grc) on how to time tag IQ  
samples output from the bladeRF? At the moment, I’m naively searching  
for  
finite strings based on the iq\_in generated from the DPSK Mod block in  
Tx.grc, so I don’t really know if I’m comparing the right samples at  
each  
time instance.

Am I missing something elementary in my setup or do I have to use  
channel  
coding to prevent errors in transmission?

I do apologize if I’m being fairly thick; I’m fairly new to DSP, SDRs  
and  
Gnuradio.

Regards,

Kamarisam

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View this message in context:  
[http://gnuradio.4.n7.nabble.com/Simple-Tx-Rx-setup-tp44544.html](http://gnuradio.4.n7.nabble.com/Simple-Tx-Rx-setup-tp44544.html)  
Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).

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**Author:** ![Kamarisam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/9fc29f/32.png) [@Kamarisam](https://www.ruby-forum.com/u/Kamarisam)\
**Post date:** [November 4, 2013, 4:01pm UTC](https://www.ruby-forum.com/t/simple-tx-rx-setup/237295/2 "2013-11-04T16:01:12Z")

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Kamarisam,

I really hope you’re using an attenuator in between the two devices.  
I’m not terribly familiar with bladerf’s frontend but if it works  
similar to our devices,  
you’ll fry them if you don’t attenuate the TX signal going through the  
SMA cable.

Cheers,

Moritz