[Hackrf-dev] Is my new (old) HackRF Deaf?

Tue Jul 11 03:41:41 EDT 2017

Hey,

So, a little DSP background.
------

Keep in mind pretty much all the SDRs now output complex (I/Q) / Quadrature
samples. This means two things. Nyqust BW = Sample Rate, and everything is
centered at 0 frequency digitally. Basically, where you would think of a
bandwidth control before, use sample rate now. Bandwidth usually refers to
a filter applied to the sample_rate (remember, bandwidth=sample rate) sized
chunk of spectrum.

The SDR takes that original spectrum (10M of complex bandwidth centered at
90Mhz in your case, down converts it to baseband, and sends it to the PC.
GR is plotting [-5M, 5M] (but helpfully overlaying the original tuned
frequency for you, since you have told it where that is in the QT GUI sink.)

Also, unlike your (probably) superhet recievers, most SDR devices,
including the hackrf are direct conversion. This type of receive has a
couple drawbacks over the superhet ones. (There are pros too usually
size/weight/power/cost.) One con is DC leakage. That is the bigger spike
you see at the center. You can avoid it by offset tuning. I think the ham
folks would call this a VFO. Basically it, in software, will take the
spectrum from a point not at 0, shift it down to 0, and bandpass filter it.
Then do the FM/AM/ec demod. (You can also simply overpower the spike with
your carrier, if possible, but the hackrf has a rather large amount of
leakage vs others so it's not always practical, and it would need to be at
the antenna power, not post digitization.)

If you insist on using Windows I think SDRConsole might work a bit better
for you, and is probably setup to be a little more friendly to someone
coming into the SDR thing from a ham background or someone who is not very
used to a Linux environment. However setting it up requires using zadig,
but if you got it working with sdr#, it should already be setup. Also I'll
say if you want to do hammy things, like receive AM, N/WB FM, SSB, etc.
these software packages are what your looking for, not something like
gnuradio. They usually have the point and click VFO/offset tuning setup, so
you pick you modulation, click on the center, drag the box or enter the
bandwidth you want for the demod, and you get data. Gnuradio is more akin
to a box of wires, components, and tools you will need if you want to build
your own radio, and many pages of manuals for each independent piece. Its
an awesome tool if you want to experiment with building different kinds of
radios, perhaps a bit overkill or a bit much if you just want to use one.
(At least till you get your feet wet in the SDR world, and start thinking,
man wouldn't it be cool if sdr#/SDRConsole/gqrx could do XYZ, and then
realize GR provides you the tools to do just that.)

I'll also mention there is a Pentoo live USB stick image you can download
and boot into with all the drivers and such ready to go for a Linux setup.
Just plug it in and boot off it. If you do try this the best (imho) Linux
version of the SDR#/SDRConsole radio receiver app flavor, is gqrx, which
should come on the Pentoo image by default.

If you do keep playing with GR, you should sign up for the discuss-gnuradio
mailing list which is very active, and can help with some of your gnuradio
questions.

----
So for your current setup:

BW will control the digital bandpass filter on the hackrf. It will not do
what you want. Try setting that equal to the sample rate(samp_rate by
default), and changing the sample rate to something like 4M. From your FFT
it looks like you have possibly two weakish FM carriers visible, but your
bandpass is set to only a meg or two, so you might be missing some on the
side, that are higher power.

You'll need to adjust the gain sliders. The help documentation(or see [1])
should describe what they mean for the hackrf, of which there are three.
"RF gain" is a toggle for the rf amp. Leave this one off/0. The other two,
the bb and if gain I believe, you can play with, setting both to about 16
should be ok to start, however I find setting the if gain to 32 and the bb
to about 4 seems to work better for me.

[1]
https://www.reddit.com/r/hackrf/comments/49aa2i/using_gain_controls_with_osmocom_sourcesink_in/

-Anon

On Jul 11, 2017 12:36 AM, "Jerry" <jsternmd at att.net> wrote:

> Jake
>
>
>
> Thanks for the sound advice.  I have had spectrum analyzers and learned
> early to be careful with nearby RF sources ☹
>
>
>
> Right now I am getting a wide confluence of signals between 98.5 and 101.5
> on the FFT.  If it were my SA I would narrow the bandwidth to improve the
> signal resolution but on the Osmocom Source changing Ch0 Bandwidth from 10
> Hz to 500 Hz doesn’t appear to change the FFT display noticeably.
>
>
>
> Attached is a picture.
>
>
>
> Jerry NY2KW
>
>
>
>
>
> *From:* HackRF-dev [mailto:hackrf-dev-bounces at greatscottgadgets.com] *On
> Behalf Of *Gavin Jacobs
> *Sent:* Monday, July 10, 2017 6:22 PM
> *To:* hackrf-dev at greatscottgadgets.com
> *Subject:* Re: [Hackrf-dev] Is my new (old) HackRF Deaf?
>
>
>
> Jerry,
>
> Learning how to use Ubuntu, and Gnu, and HackRF is a challenge! I went
> down that path about a year ago. The issue you describe hits every new
> user. When you are running GNU radio, you have to turn up the IF gain to
> about 40 - it defaults to 0. Also, turn up the BaseBand gain to about 30.
> Leave the RF gain at 0 (that setting is confusing; a value of 0 just means
> the RF LNA is left off; 14 means it is on; but you rarely need it on).
>
>
>
> Also, a word of caution. Since you are a ham, you likely have an HT or a
> base station. You have to take care to never exceed the maximum field
> strength anywhere near the HackRF. I don't recall the exact spec, but
> basically if you transmit with a 5 Watt HT, right next to HackRF, you can
> fry the RF front end.
>
>
>
> Hope that helps.
>
> Jake
>
>
> ------------------------------
>
> *From:* HackRF-dev <hackrf-dev-bounces at greatscottgadgets.com> on behalf
> of Jerry Stern <jsternmd at att.net>
> *Sent:* July 10, 2017 2:54:16 PM
> *To:* hackrf-dev at greatscottgadgets.com
> *Subject:* [Hackrf-dev] Is my new (old) HackRF Deaf?
>
>
>
> Is my HackRF deaf?  I am a ham radio hobbyist and I bought a HackRF One to
> enhance my deeper learning of SDR but also as a broadband RF source.  To my
> dismay, installing the software has become days of learning Ubuntu basics
> and dealing with instructions that are at times outdated or nuanced towards
> a person with much more than basic Linux skills.  So, I gave up on Ubuntu
> only because it was faster for me to install and test with Windows 7.   My
> HackRF One (GreatScott) must have been a leftover as the firmware was dated
> 2014(August).  I installed the latest version HackRF tools and updated the
> firmware to Feb 2017.  I followed Mike's video tutorial for creating a
> basic GNU flow for FM and also installed SDR#.  I have very strong FM
> broadcast stations in my area which I can easily demodulate with my Rigol
> Spectrum analyzer using the ANT500. However both with GNU and SDR# my
> HackRF appears deaf in FM broadcast mode.  I read that a few years back
> there may have been some issues with cold solder joints on the HackRF
> pcb....  I have a lot of test equipment - from RF generators up to 2 GHz,
> etc but before I go that route is there something I am perhaps missing in
> my setup.  Not sure where or what details to provide here without
> overloading my question further .
>
>
>
> Thanks
>
>
>
> Jerry
>
>
>
>
> Sent from my iPhone
>
> _______________________________________________
> HackRF-dev mailing list
> HackRF-dev at greatscottgadgets.com
> https://pairlist9.pair.net/mailman/listinfo/hackrf-dev
>
>
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