[Hackrf-dev] Sensitivity

[Iluta V]

Dear McDonald,

Thank you for sharing this, and could you suggest more about filters:

Which filters are best suited for RX in sub 1 Ghz area, since on Gnu Radio
3.7.7 version there are 14 different filters.

I made a simple grc file consisting of Source - Throttle - Sinks, and how
the best both types of Filters would fit there?

Since signal quality in outdoors is by far better than indoors with all
other interference around,  just for me it means sitting in a car in minus
degrees outside to catch quality signals, until laptop batteries die.

Which would be prefilters you mentioned, and maybe you could have a sample
for prefilter usage?

Does it make sense to add filters for RTL as well,  to get even better
signal quality, or your suggestion to use prefilters and filters for HackRF
only?

(sorry, just I'm not a specialist in IT or SDRs at all).

Best regards,

Iluta



On Tue, Jan 20, 2015 at 4:28 PM, McDonald, J Douglas <jdmcdona at illinois.edu>
wrote:

> I have not measured numerically the sensitivity of these tyoe devices, but
> have comapred them.  In actual use the seinsitivity of the HackRF and
> the RTL dongles are similar, using both SDR$ and Gnuradio.
>
> Both devices are limited by a too-low number of digitized bits.
> It is extremely important that the gains be set correctly. You have to
> have the HackRF's multiple gains split correctly or it can limit even in an
> early stage, resulting in all sorts of image problems, etc.
>
> Try experimenting with widely varying signal levels and gain settings.
>
> I find that for signals well prefiltered performance is extremely similar,
> but if not, the HackRF is  vastly (no exaggeration) inferior. Note that
> "well" implies really great rejection of unwanted signals from 0.3
> to 10,000 Mhz. I have no idea what is happening above the
> max frequency spec of either, but for HackRF I suspect the
> worst in terms of intermodulation problems. Computers with the current
> rage RF networking
> running can seriously overload these gizmos. So use prefilters and
> be SURE that they are rejecting all the microwave stuff you are
> actually using. Test them. If you are working below a GHz, your filter
> may not be killing enough up in the upper reaches.
>
>
>
>
> Doug McDonald
>
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>
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