[Hackrf-dev] FW: deaf HackRF

[Stephen]

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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