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

[Hakan Tolgay]

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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