[Hackrf-dev] HackRF Jawbreaker Bugs

[Michael Ossmann]

On Fri, Aug 02, 2013 at 10:18:22AM -0400, Russell Hande wrote:

>

> * Tuning glitch in upper frequencies:

> 

> Notice what happens when the center frequency rolls over at the MHz

> level.  This does not occur at lower frequencies, such as HF, FM, VHF,

> ect.

> 

> http://youtu.be/4v6ughu0pWU


I'm still trying to figure out what is going on here, but I can
reproduce a similar glitch.


> * FM at 1.7ghz:

> 

> You don't see many FM stations because I have an FM trap installed,

> but the entire 89-108 spectrum appears here. The tuning glitch

> described above is also observed in this video.

> 

> http://youtu.be/aTucSSaTvuk


This is a result of the third harmonic of the front-end LO.  The default
IF is 2600 MHz.  2600 - 1700 = 900 LO.  900 * 3 - 2600 = 100 MHz, right
in the middle of the FM broadcast band.  This can be avoided with
selection of a different IF.


> * 50mhz Noise:

> 

> I've contacted Mr Ossmann directly about this yesterday, but I wanted

> to share with the mailing list as well. We know about the noise

> induced by the system every 50MHz, but what is odd is if we use a

> sampling rate below the specification of the chip (such as 2msps as

> demonstrated in the video), the noise is significantly reduced.

> 

> http://youtu.be/Oy_yUJAFf04


I haven't been able to reproduce this.  Anyone else?


> *Super High Frequency tuning issue:

> 

> I don't even know how to describe this. Its like the tuning glitch

> mentioned above got worse.

> 

> http://youtu.be/liXdkUHC6tk


I agree that this is probably the same tuning glitch, but it seems to
get progressively worse at higher frequencies.  I'm suspecting the
tuning code in firmware.