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

[David Goldstein]

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.
On Apr 18, 2016 10:12, "O.T. Powell" <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>
>> To: 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 PowellEE Engineering TechM: 386.299.6991
> <386.299.6991>otpowell at gmail.com*
>
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>
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