[Hackrf-dev] FW: deaf HackRF

[王康]

Maybe that's why mossmann is working on a LNA extension board for HackRF.

On 2015年1月20日 周二 at 04:25 Stephen <refsmmat at gmail.com> wrote:

> Hi Tom,
>
>
>
> Thanks for the reply.
>
>
>
> The RX sensitivity figure I quoted is dBm – ‘Decibels above a MilliWatt’.
> -95dBm is 95 db below a MilliWatt, wheras -127dBm is 127 db below a
> MilliWatt.
>
> This test was conducted with an RF signal generator.
>
>
>
> Regarding the test, to register minimum scale on the SDR# spectrum, the
> HackRF required -95dBm , the RTL2832 required only -127dBm.
>
>
>
> Expressing this as microvolts instead of dBm, the equivalent level in
> microvolts (to register the same scale on SDR#) are:
>
>
>
> 0.1uV  for the RTL2832
>
> 3.5uV for the hack RF
>
>
>
> Accordingly, The HackRF requires considerably more signal to register the
> same scale on SDR#.
>
>
>
> I discovered this performance limitation when  I attempted to try to
> receive NOAA weather satellites, I found HackRF barely registered, wheras
> the RTL2832 registered a strong signal for the same satellite pass  on the
> same antenna.
>
>
>
> I appreciate you are trying to help & I don’t mean to be rude by
> contradicting you,  but the HackRF I have is definitely ‘deaf’.
>
>
>
> Regards,
>
> Stephen
>
>
>
>
>
> *From:* Tom Buelens [mailto:tom.buelens at gmail.com]
> *Sent:* Monday, 19 January 2015 8:23 PM
> *To:* Stephen
> *Subject:* Re: [Hackrf-dev] deaf HackRF
>
>
>
> Hi Stephen,
>
>
>
>
>
> I might be mistaken but I actually think the numbers you mention show that
> the HackRF is better at receiving the signal.
>
> You see, an attenuation of -105 dBm is resulting in a smaller signal then
> -69dBm. Please also see here:
>
> http://en.wikipedia.org/wiki/DBm
>
>
>
>
>
> Cheers,
>
> Tom
>
>
>
> On Mon, Jan 19, 2015 at 2:36 AM, Stephen <refsmmat at gmail.com> wrote:
>
> Hi,
>
> Ive just bought a HackRF, but I have found  RF performance is poor.
> Compared to a $12 USB RTL2832 SDR, it is deaf by about 32-36dB.
>
>
>
> The tests were done with an HP 8922 test set & an unmodulated carrier at
> 137.5MHz. The test was the generated RF signal required for both devices to
> achieve the same scale level in SDR#.
>
>
>
> RTL SDR                  HackRF     Difference
>
> Scale1   -127dBm              -95dBm               32dB
>
> Scale2   -115dBm              -79dBm               36dB
>
> Scale3  -105dBm               -69dBm                36dB
>
>
>
>
>
> The tests were done with max gain on both devices, but with the HackRF AMP
> off.
>
>
>
> I have seen from posts that others have had this problem – related
> soldering of RF switches in the manufacturing process.
>
> Can anyone provide further details on the fix  or suggest a resolution
> please?
>
>
>
>
>
> Thanks,
>
>
>
> Stephen
>
>
>
>
>
>
>
>
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>
>
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