[Hackrf-dev] High Noise Floor

[Dominic Spill]

On 5 March 2016 at 05:08, Jay Radcliffe <jay.radcliffe at gmail.com> wrote:
>
> I am working with an older Jawbreaker with current firmware (2015.07.2) and
> am seeing something odd.

So that we can rule it out, have you performed the antenna
modification?  It's detailed here
https://github.com/mossmann/hackrf/wiki/Jawbreaker#set-your-jawbreaker-free

> When I just run a simple source -> FFT in GRC the
> baseline of the noise floor is quite high (around -40db). When I take the
> antenna off it drops down to -90db. Tried several antennas with same
> results. I have tried the FM broadcast band, 440mhz and 915mhz. Typically
> when I see examples of the FFT in a demonstration or presentation the noise
> floor is in the -80/-90 range. I am using the default setting for the FFT
> and osmocom source blocks. Anyone have any ideas about this or have see this
> behavior before?

What happens when you run other tools, such as gqrx to listen to
broadcast FM?  Or dump1090
(https://github.com/itemir/dump1090_sdrplus) to see ADS-B messages?
Do they work, or is the noise causing a problem for them too?

Does turning the amplifier on/off change things?

Thanks,
  Dominic