[Hackrf-dev] TX Trouble

[Chuck McManis]

I second the suggestion that if you have a second HackRF or spectrum
analyzer you look at what is coming out of the antenna. That will tell you
if your flow graph is correct.

Also, if you're just trying to clone a car key fob (unlike say a garage
door opener) you should be aware that the key fob radio usually sends a
rolling code (it changes every time) so you cannot just record it, and then
replay it, and expect to open a car door with it.

--Chuck

On Tue, Oct 17, 2017 at 7:36 AM, <wiemeyer at nehp.net> wrote:

> Hello All,
>
> I'm still having trouble transmitting from file, a car door clicker
> waveform that I saved, similar to one of the tutorial videos.
>
> For one thing, the TX light comes on when I start the flowgraph, but when
> I close it, the light stays on.  Is that normal?
>
> And, generally speaking, what are things to look for when debugging TX
> problems?  I can think of two problems:  I'm not transmitting with enough
> power, or I messed up the waveform somehow when I recorded it.
>
> Regarding the first, I've tried setting the RF gain as high as it will go,
> and I've tried different antenna lengths.
>
> Regarding the second, I'm worried that I may have saturated HackRF when I
> recorded the waveform.  Is there a way to tell, if I view the recorded
> waveform in the QT GUI time domain plot?  Anything above 1 V or below -1
> V?  I guess the waveform would look clipped, but it appears so quickly,
> that it is hard to tell.  Same question on transmit:  how can I tell if I
> am saturating?
>
> I'm also aware of the trick in the video about multiplying by a constant
> to increase SNR.  Any other ideas?
>
> Thanks,
>
> Brian
>
>
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