Re: [Discuss-gnuradio] Error in testing benchmark_tx/rx.py

[Patrik Tast]

Hi,

 

Q1: What antennas are you using (designed for what frequency)

Q2: How far away is TX -> RX

 

A half wave dipole antenna @ 450 MHz is ~333 mm (wavelength 667 mm).

Add a 4:1 BalUn (COAX or Sleeve) as explained in wikipedia

http://en.wikipedia.org/wiki/Dipole_antenna

 

I would add ferrites (any you can find) also at the antenna

 

Patrik 

----- Original Message -----

From: Songsong Gee

To: gnuradio mailing list

Sent: Saturday, November 19, 2011 15:48

Subject: Re: [Discuss-gnuradio] Error in testing benchmark_tx/rx.py

I found a clue for it.

in receive_path.py, there is two thresholds

one is passed to demod_pkt class in pkt.py

and one is used in receive_path.py 

I did set both threshold with value -30 (dB)

Then it goes into another step (but still some python grammar error occurs, but it's hopeful)

2011/11/19 Songsong Gee <address@hidden>

FYI,

this is a fft scope WIHTOU TX (uhd_fft.py -f 450e6 -A TX/RX)

and this is the fft scope WITH TX (benchmark_tx.py -f 450e6 -A TX/RX)

as you can see, gain increased when TX is turned on.

However, it seems that benchmark_rx.py cannot catch those signals.

benchmark_rx.py -f 450e6 -A TX/RX

======================================================

linux; GNU C++ version 4.4.5; Boost_104200; UHD_003.004.000-eb11b05

>>> gr_fir_ccf: using 3DNow!

-- Opening a USRP1 device...

-- Loading FPGA image: /usr/local/share/uhd/images/usrp1_fpga.rbf... done

-- Using FPGA clock rate of 64.000000MHz...

No gain specified.

Setting gain to 25.750000 (from [0.000000, 51.500000])

UHD Warning:

    The hardware does not support the requested RX sample rate:

    Target sample rate: 0.050000 MSps

    Actual sample rate: 0.250000 MSps

Symbol Rate:         25000.000000

Requested sps:       2.000000

Given sample rate:   250000.000000

Actual sps for rate: 10.000000

Requested sample rate: 50000.000000

Actual sample rate: 250000.000000

======================================================

it stops here and prints *NOTHING* whenever I set tx-gain and rx-gain with about 30 dB and 50 dB.

My assumption is that a demodulator does not consider signals as data.

Rather than, they are considered as noise whose signal strength is too weak compared to a certain threshold

which distinguish meaningful data and noise

Is my assumption is right?

Still I am curious because this situation occurs with very high tx-gain and rx-gain, also.

2011/11/19 Songsong Gee <address@hidden>:

> I'm currently testing UHD.
> I use two USRPs with one SBX on each.
> and I got GNU Radio 3.5.0rc0 on Ubuntu 10.10 and benchmark programs
> supporting UHD.
>
> When I run benchmark_tx/rx.py, however,
>
> address@hidden $ ./benchmark_tx.py -f 410M
> address@hidden $ ./benchmark_rx.py -f 410M
>
> I can see 'dots' representing a signal is transmitted on a transmitter side.
> but a receiver does give nothing on a screen.
>
> and the screens on the both side, I got this message.
> ====================================================
> No gain specified.
> Setting gain to 5.750000 (from [-20.000000, 31.500000])
>
> UHD Warning:
>    The hardware does not support the requested TX/RX sample rate:
>    Target sample rate: 0.050000 MSps
>    Actual sample rate: 0.250000 MSps
>
> Symbol Rate:         25000.000000
> Requested sps:       2.000000
> Given sample rate:   250000.000000
> Actual sps for rate: 10.000000
>
> Requested sample rate: 50000.000000
> Actual sample rate: 250000.000000
> ====================================================
>
> What did I do wrong?
>
> 1. Wrong frequency option (either tx or rx)
> 2. Wrong/Unspecified sample rate option (either tx or rx)
> 3. Too weak signal strength to catch
> 4. Or...?
>
> --
> Seokseong Jeon, PhD Candidate
> Communication & Networks Lab
> IT Convergence Engineering (ITCE), POSTECH, Korea
> +82 10 8338 1229, gee.songsong at gmail . com
>



--
Seokseong Jeon, PhD Candidate
Communication & Networks Lab
IT Convergence Engineering (ITCE), POSTECH, Korea
+82 10 8338 1229, gee.songsong at gmail . com

--

Seokseong Jeon, PhD Candidate

Communication & Networks Lab

IT Convergence Engineering (ITCE), POSTECH, Korea

+82 10 8338 1229, gee.songsong at gmail . com

---

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