I Broke My HackRF Portapack! Here's How Not to

This is the hackRF Portapack a handheld  SDR transceiver capable of manipulating radio   waves, decoding digital signals and giving you an  insight into the invisible electromagnetic world   around us it does however suffer from a huge flaw  that can render it apparently completely unable   of receiving anything I broke my HackRF with and I  didn't even realise it at first that's how easy it   is to do accidentally. To explain what the problem  is I first have to talk about how the HackRF works when you use a receiving application on  the Portapack you have three controls for   adjusting the strength of your signal which is  also called gain in radio language if you do not   adjust these you might not receive anything  I have a worse than ideal reception the gain   settings affect different steps of the signal path  in the receiver the first option is LNA which is   short for low noise amplifier and it's placed at  the intermediate frequency stage of the receiver   this is the main gain adjustment to get a good  signal to noise ratio the second option is VGA   which is short for variable gain amplifier and  it's located at the baseband stage this can be   used to fine tune levels but it also amplifies  signal noise I think of this more as a volume   adjustment into the application the number values  of these two settings define how much they gain   the signal in dB which is short for decibel and is  a measurement value used among other things for   radio signal strength you will need a good balance  of these two settings to get good decodes in the   different apps start out with both values at 16  and increase them roughly equally to find the best   settings for your situation too low of a gain and  the signal will disappear in noise and too high   of a gain and you might get a distorted signal  or ghost signals turning up in incorrect places   if you push the DFU button on the top of the HackRF Portapack twice it will open a debug menu that   among other things shows RX saturation percentage  RX is a commonly used radio abbreviation for   receive whereas TX would be transmit this receive  saturation percentage shows you how much signal is   going into the decoding application and can help  you adjust the signal strength so that it doesn't   peak out at 100% or is too low at 0% press the  DFU button once more to close the window after   having adjusted your gain settings there is a  third setting called amp this can be toggled on   or off and controls a low noise amplifier which  is placed just near the antenna connector on the   HackRF when enabled this will boost the  incoming signal strength by a fixed amount of   about 11 DB this amplifier is the main problem of  the HackRF because it is extremely sensitive   and it can very easily be destroyed without you  even knowing what cost it it takes less than   a volt of electricity entering the antenna port to  destroy the amp which could be caused by something   as simple as connecting an antenna cable with a  bit of static voltage buildup or even having a   strong transmission nearby to determine whether  or not your amp has been fried open the audio   receiving application and tune to a known signal  with the amp turned off like a local fm broadcast   station now turn the amp on if the signal strength  lowers significantly this means your amp is broken   and it's now functioning as an attenuator instead  of an amplifier if the signal strength increases   then the amp is still working fine chling the  amp off bypasses it in the circuit this means   that even if your amp is broken you can still use  your HackRF you just have to turn the amp off   otherwise you won't be receiving anything and if  your amp isn't broken it is still best practice   to have it be turned off by default unless you  actually need be careful what you connect to your   HackRF turn the HackRF off while connecting  and disconnecting antennas and if you connect   outside antennas make sure to ground them first  so that you remove any static buildup it is also   possible to use external low noise amplifiers  instead of the built-in one like this 20 dB   amp from open source SDR lab which is powered  by a USB cable and of course the best thing you can   do to increase signal strength is to use a proper  antenna for the frequency you're trying to listen   to and to have it up high and clear of surrounding  buildings trees or hills and local noise sources now if you have steady hands and are  really good at soldering you can replace the   broken part on the circuit board but it can  just as easily be fried again in the future   so there isn't really a good solution to this  problem or is there HackRF is an opensource   hardware project just like open source software  projects where you can download the source code   and build it yourself this means that the plans  for building a HackRF are freely available   on GitHub and anyone can source the parts and  build one while Michael Osman from Great Scott   gadgets is the designer of the board and also  sells hacker from his website there are also   third party manufacturers who are making HackRF boards from the same design files just   like open source software projects there have  been small changes to the design over the last   10 years that the project has existed this is  why you see boards sold that are labeled R9   for instance indicating that it is revision 9 of  the design mostly these changes have been done   to make sure that all the components on the board  are ones that are readily available for purchase   currently and just like opensource software  projects you can also fork a hardware project   and make design changes one such design fork is  made by a guy named Clifford Heath and he has   redesigned the circuitry around the problematic  amp along with a few other changes of components   and minor improvements by introducing a few  protective diodes in the circuit the amp is   protected from voltages above its operating limits  this prevents the amp from being fried by simple   static discharges and even higher voltages  entering the antenna a port so far I've only   been talking about the receiving chain of HackRF  but the same model of amp chip is used in the   transmitting section and can be toggled on or off in  transmitting applications this second transmitting   amp is less likely to be damaged normally but the  Clifford version of the HackRF circuit board   also puts in protection of this transmit amp you  can get the Clifford edition of the HackRF   board separately or in this assembled Portapack  version that open source SDR lab has kindly sent me I've had this for a while now and  I've not managed to break the amp and   even with the amp turned off it seems  like it's better at receiving than my   old hHackRF I'll link to where you  can buy this one down below and I hope   I've given you a small insight into  the potential pitfalls of the hacker

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Length: 8min 11sec (491 seconds)

Published: Tue Mar 12 2024