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

[Cinaed Simson]

On 04/18/2016 07:15 AM, David Goldstein wrote:
> I'm new here.  I just ordered a dc-4.3ghz rlc l-1032 filter to see how
> that works...they have lna's like this used--on ebay, FYI.

The maximum frequency of the HackRF is roughly 6 GHz. With a cutoff at
roughly 4 GHz, it passes just about everything.

Unless you have drones flying around your house, it probably won't make
much difference.

I would recommend using a 1 GHz low pass filter in general. You need to
be careful of WIFI. Band pass filters would be better but they can be
hard to find for the band you need.

See

  https://www.tindie.com/stores/gpio

or

  http://www.ebay.com/usr/iseeabluewhale

And I'd recommend AGAINST buying a LNA until after you've completed the
HackRF course

   https://greatscottgadgets.com/sdr

Lesson 5 is the operating manual.


-- Cinaed








> 
> On Apr 18, 2016 10:12, "O.T. Powell" <otpowell at gmail.com
> <mailto:otpowell at gmail.com>> wrote:
> 
> 
>         ​Thank you both for the great responses.  I have a 1090 ADS-B
>         bandpass filter as well as an LNA.  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
>     *
>     *
>     *
> 
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> 
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