[Hackrf-dev] Fwd: HacRF One & GNU - strange frequency shifting problem

Andrew Rich vk4tec at tech-software.net
Mon Aug 7 02:52:35 EDT 2017


I read it went yeah I can't really understand it 

Sent from my iPhone

> On 7 Aug 2017, at 3:53 pm, Hakan Tolgay <hakantolgay at gmail.com> wrote:
> 
> Hello all,
> 
> I am re-sending the following email since I didn't get confirmation email. Sorry if it is duplicate.
> 
> Regards,
> Hakan
> 
> ---------- Forwarded message ----------
> 
> Hello all,
> 
> I am playing with my new HackRF One which I bought at Defcon. I thought that SDR courses at https://greatscottgadgets.com/sdr/ is a good start.
> 
> I did the first diagram which Michael Ossman shows. It seems to be working great at first. However, I realize that, whenever the difference between channel_freq and center_freq is greater than 6Mhz (6e6) the result frequency was getting corrupted.
> 
> For those who don't know the first SDR lesson, my problem is, when I tried to multiply 100e6 with a frequency greater than 6e6, resulting frequency becomes something that shouldn't be. 
> For example multiplication of:
> 
> 105e6 with -2e6 generates 107e6 with no problem
> 104e6 with -3e6 generates 107e6 with no problem
> 105e6 with -4e6 generates 107e6 with no problem
> 103e6 with -5e6 generates 107e6 with no problem
> 
> but,
> 98e6 with -9e6 generates 97e6. I also checked it from the radio and it was really 97Mhz.
> 
> At first I thought that it may be because of my CPU which couldn't generate 9MHz signal. So, I drop the sample rate to 2M but it didn't work. However, the resulting frequency shifted a little bit left or rigt to the 97.0Mhz.
> 
> 
> This my be a so easy question but I really couldn't find any explanation. Any idea would help.
> 
> btw, my cpu is Intel i5-3337U
> 
> Thanks
> Hakan
> 
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