[Hackrf-dev] HackRF-dev - Response to Cinead & Douglas McDonald from O.T. Powell

[Cinaed Simson]

On 04/18/2016 07:12 AM, O.T. Powell wrote:
> 
>     ​Thank you both for the great responses.  I have a 1090 ADS-B
>     bandpass filter as well as an LNA. 

I'd recommend buying a variable attenuator and a couple of 1,3 and 6 dB
fixed attenuators and experimenting with the external LNA on a rtl dongle.

And you should figure out how much power it takes to smoke the LNA
inside the rtl dongle.


> I am looking into buying an
>     adjustable bandpass filter, or I'm sure I can make an RLC circuit
>     that serves the same purpose.  As for an external amplifier, is the
>     LNA the same thing?  Does it amplify transmitted signals as well?  
>      I am using SDR# right now, but I'm also going to try Skywave Linux
>     and the SDR package in Kali Linux.  I already have them setup I just
>     have to plug in my HackRF and start testing.
> 
> ​
> In regard to the full metal shield, I just bought the HackRF shield from
> NooElec.  Is this what you are talking about?  I am going to install
> that this week.  I also have an aluminum box coming, but was not
> planning on putting my hackRF in the aluminum box because I read that if
> you have the shield, adding the aluminum box does not add any extra
> shielding.  Do you guys think that information is accurate?  Should I
> add the sheild and then enclose the whole thing in an aluminum box?  
> 
> Can you reccommend any bandpass filters or external amplifiers that
> aren't too expensive?
> 
> I'm not sure what my sample rate or bandwidth is.  I guess I'd want the
> largest bandwidth which is 20MHz.  Sample rate, I usually go up as high
> as I can while having everything run smoothly.
> 
> Thanks guys for being patient, I'm still learning.  Most of you sound
> like RF guru's.  lol.
> 
>      
> 
>      
> 
>     ​
> 
> 
>     Today's Topics:
> 
>        1. Re: HackRF-dev Digest, Vol 42, Issue 10 (Cinaed Simson)
> 
> 
> 
>     From: Cinaed Simson <cinaed.simson at gmail.com
>     <mailto:cinaed.simson at gmail.com>>
>     To: hackrf-dev at greatscottgadgets.com
>     <mailto:hackrf-dev at greatscottgadgets.com>
> 
> 
>     On 04/15/2016 06:15 AM, McDonald, J Douglas wrote:
>     >
>     > In my opinion the HackRF receive is fairly poor because of the
>     conflation
>     > of two things:
>     >
>     > only 8 bits
>     >
>     > inadequately steep frequency skirt filters
>     >
> 
>     The HackRF doesn't have a front-end. Either buy a band pass filter or
>     construct one using gnuradio.
> 
>     It's highly recommend to use an external band pass filter with an
>     external amplifier.
> 
>     Also, you didn't indicate which software package you were using - the
>     bandwidth or sampling rate.
> 
>     > This means there are spurious responses all over the place.
>     > These are really really a nuisance.
>     >
>     > Also, the connections to the box are not well done: any serious RF
>     device needs
>     > a full metal shield with all connections bonded to the box, not
>     sticking
>     > through holes.
> 
>     See Michael Ossmann's tutorial on the HackRF
> 
>       https://greatscottgadgets.com/sdr/
> 
>     >
>     > On the short wave bands I can get a usable signal from my amplified
>     > outside antenna by touching the shield of the RG6 coax to the
>     input connector,
>     > and the actual differential mode signal (center conductor versus
>     shield) does not
>     > fully swamp that.
> 
>     Isn't RG6 75 ohm cable? The HackRF unlike the RTL-SDR dongle is a 50 ohm
>     device. It's not a big deal provided you already have a good impedance
>     match with the antenna. If you reflect roughly 10 mW of power back at
>     the HackRF, you'll smoke the RF amplifier on the HackRF - see the link
>     above.
> 
>     Regarding the antenna problem, did you try a different antenna -
>     preferably one which sees the same ground as your computer?
> 
>     In any case, nothing you described above has anything to do with the 8
>     bit ADC.
> 
> 
> 
> -- 
> *
> *
> *
> O.T. Timothy Powell
> EE Engineering Tech
> M: 386.299.6991 <tel:386.299.6991>
> otpowell at gmail.com
> *
> *
> *
> 
> 
> _______________________________________________
> HackRF-dev mailing list
> HackRF-dev at greatscottgadgets.com
> https://pairlist9.pair.net/mailman/listinfo/hackrf-dev
>