[Hackrf-dev] Low pass filter lesson 1

[Chuck McManis]

Hi Matteo,

It is the difference between "baseband" and "RF". If you take an RF signal
that is at 100Mhz and has a bandwidth of 2.5Khz,  you can mix it with
another signal at 100Mhz and that will produce two outputs, one at 200Mhz,
and one at 0Mhz. It will still have a 2.5Khz bandwidth so on the low end it
will be between 0 and 2.5kHz so a low pass filter is needed.

This is the fundamental principle behind radios.

--Chuck


On Tue, May 8, 2018 at 5:59 AM, Matteo Terzi <matteo.terzi97 at gmail.com>
wrote:

> Hi all,
> I'd like to know why does Micheal Ossmann use a Low Pass Filter in the
> Lesson 1 (https://greatscottgadgets.com/sdr/1/ --> minute 22:00).
> He says that in that way just frequencies near to the zero Hz can pass but
> it doesn't make sense....how radio frequencies can pass if they have a
> value of MHz??
> Thanks
>
> Matteo
>
> --
> Matteo TERZI
> Google Gmail Member
>
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