Re: [Discuss-gnuradio] Just wondering why?

[Cinaed Simson]

On 11/01/2017 05:55 PM, Cinaed Simson wrote:
>>>
>>> Note, you should set the RF again to 0 when receiving. There's frontend
>>> on the hackrf and you run risk of smoking the receiving RF amplifier if
>>> there's a strong RF transmission nearby.
>>> Also, the RF gain is either 0 or 1 - on or off.
>>>
>>> See the hackrf tutorials greatscottgadgets.com website.
>>>
>> Not a problem for me most of my testing is done with my test set, the RF 
>> gain 
>> set at 14 dB means I can receive signals down to -115 dBm, I tend to use 
>> signals at around -80 dBm so I am far away from the -5 dBm maximum for the 
>> rf 

No, setting the RX gain to 14 dB means you haven't done your homework.

Take a look at the output of

   hackrf_transfer

Note

  # RX/TX RF amplifier 1=Enable, 0=Disable.

That is, the RF gain is either on or off for both receiving and
transmitting - it's all or nothing - you don't get to choose the level.

The LNA and VGA should really have sliders since the increments and
maxims are different for each gain - and the VGA is different for
receiving and transmitting - and they're the gains you may want to
adjust after you start gnuradio

  # RX LNA (IF) gain, 0-40dB, 8dB steps
  # RX VGA (baseband) gain, 0-62dB, 2dB steps
  # TX VGA (IF) gain, 0-47dB, 1dB steps

This is also covered in the hackrf tutorials.

-- Cinaed