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KerberosSDR • Re: Compatible image

I think there's a big "gotcha" to the approach you're suggesting (modifying a Kerberos RPi image). Given the state of these embedded-ARM boards, I think you're likely to find that the RPi image is in the wrong format, or has an incompatible kernel, or is missing essential drivers, or its device-tree image causes the kernel to do all the wrong I/O to all the wrong places in your hardware and cause it to sprout wings and fly out the door in a rage. ;)

I'd suggest going about it in the opposite direction:
  • Start with a clean copy of an image intended to work with your board (Debian, Arch, or whatever).
  • Follow the instructions in the KerberosSDR quick-start document, for installing their software on a PC. These steps are quite generic Linux operations and should work on a Debian (for example) image on your board.
  • Customize their "run" script for your board, and (if you desire) hook it up to systemd (or whatever your distribution uses) so that it starts up at boot time.]
The advantage to this approach is that you can start with a "known to run properly" image, and go through a fairly "vanilla" process of installing and compiling software packages to build the Kerberos software on your board.

One disadvantage is that the install process is likely to take a while, and you may need to "throw some resources at it". I've gone through this process 2-3 times to build a working image for a Libre Computer La Frite board. It's generally an overnight build (some of the Python stuff takes a long time to build!) and I had to add an external drive with several GB of swap space to keep the C compiler from running out of memory and OOM'ing. Once the software built, though, it has run OK.

Another disadvantage is that you won't have the neat "look for an access point on your phone and attach to it" auto-start script that the Kerberos people provide... until you pull a copy out of their image and tweak it to run on your distribution.

Statistics: Posted by AE6EO — Fri Dec 06, 2019 2:35 am

RTL-SDR Discussion • Re: Newbie : listening 3Khz to 148 Khz with upconverter ?

The best SDR receiver for 0 Hz to 96 kHz is to use good quality sound-card "line-in" input.

With hi-fi 24-bit sound-card which allows to sample at 192 kHz you can receive 0 - 96 kHz with almost 140 dB dynamic range. This is very high. Such dynamic range is available only in top-class SDR receivers. But you can get it with almost any, even cheap sound-card.

To get best performance and dynamic range, you're needs to buy high-end studio-grade audiophile sound card, such as E-MU or something like that. The parameters that you needs to take into account are:
- ADC resolution bits
- sample rate (higher sample rate = more wide bandwidth coverage)

Note, you're don't needs DSP and other effect, just best audio parameters.

But you can start even with cheap integrated sound-card, which is available at almost any computer these days. It will have a bit worse dynamic range and noises, but still works very good for such purposes.

In order to use it, you're needs to install HDSDR software:
And connect antenna into "line-in" jack of your sound card.

In some cases you may needs LNA and BPF for better sensitivity, but in most cases sound-card already has a good enough sensitivity and dynamic range to work directly with antenna with no LNA and filters.

Statistics: Posted by radiolistener — Thu Dec 05, 2019 8:49 pm

KerberosSDR • Compatible image

I was wondering if someone could help me run/adapt the existing rpi images on other devices such as usb armory mark II which has i.MX6ULZ ARM cortex A7 processor and comes with Debian 9 stretch image ( or arch linux ). Thank you

Statistics: Posted by Antiaeriana — Thu Dec 05, 2019 5:04 pm

Troubleshooting Help • Re: «No device selected», cannot get SDR# to start.

do you run, install the .bat file in the sdr# folder?

Statistics: Posted by Username — Thu Dec 05, 2019 9:14 am

RTL-SDR Discussion • Re: Newbie : listening 3Khz to 148 Khz with upconverter ?


Yes you can.
Results may be good or not be too good.
I've used similar and a LPF in front helped a lot by getting rid of unwanted spurious signals.
The antenna does not need to be big, just give a good signal to noise.
The best antenna I have for LF is a discone! It was the only one I had that received the Russian "Alpha" stations 11.905-16.881KHz.
You must be prepared to experiment.

Statistics: Posted by alanzfq — Thu Dec 05, 2019 7:42 am

RTL-SDR Discussion • rtl-sdr dongle V3: Accessing the 28.8 MHz reference


I am trying to sample the on-board 28.8 MHz reference to feed that clock signal into a counter/divider. I have put a jumper on the 0.05" 2x2 clock selector footprint to route the clock signal to the 2 mm expansion pin row at the edge of the board. This appears to work, but the signal at the CLK pin (expansion pad) does not look like what I would expect to see at the output of a TCXO.

Is there a tap and/or coupling capacitor between the TCXO output and the CLK pin? The signal I get certainly looks like there is. Unfortunately I could find neither a schematic of the dongle, nor the relevant specs of the CLK signal in the V3 datasheet. I'd like to know what signal I should expect on that pin in order to properly design the front-end of my counter/divider.

Best regards and thank you!

Statistics: Posted by papo — Thu Dec 05, 2019 6:48 am

RTL-SDR Discussion • listening 3Khz to 148 Khz with upconverter ?

Yes, If the upconverter is not limited by a High-Pass and really passes all signals received to the mixer and provides an upconversion. You can verify receptions using one of themany strong time reference signals closest to you, e.g. DCF-77 on 77.5 kHz in Mainflingen Germany, which are used e.g. by clocks as reference.

Reception also requires that you have an antenna that provides suffiently strong signals at frequencies below 100 kHz. Since at 0.1 MHz the wavelength is 3000 m, even 10 to 20 m wire are short compared tothe wavelength. See my previous comments here viewtopic.php?f=4&p=13029#p13028.

PS: These comments are no tintended to discourage you or anyone, but I am trying to point out that at such low frequencies, you can only try to find the best compromise. Due to the much larger dimensions of the wavelength, when compared to a few 10m at shortwave, you cannot built a halfwave dipole or 1/4 wave groundplane (Eifeltower would be good for about 200 kHz).

Alternatives to wire antennas are ferrite antennas (a coil on a ferrite rod) used in radios that provide LW reception, or you untuned coil often called loop antenna. Ferrite antennas are also used for MW radios, but I have never checked if the ferrite rods used for MW work also well on LW or lower frequencies.

Statistics: Posted by snn47 — Thu Dec 05, 2019 4:49 am

KerberosSDR • Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

WA4OSH wrote:
Wed Dec 04, 2019 9:47 pm
So the four Rafael Micro R820T2 (24 - 1766 MHz) RTL-SDRs are tied together with a USB Hub. So you would use four RTL-SDR source blocks? How do you select them in the source block?

--Konrad, WA4OSH
I never really use the RTL-SDR source blocks in GRC since I prefer gr-osmosdr. You'd select them by device index or serial number. Device string would be something like "rtl=0" for the first one or "rtl=3" for the last one. You can replace the single digit with the serial number of the specific rtl to guarantee you're picking the right radio since the device index might not necessarily line up with the arrangement on the PCB.

Statistics: Posted by ckoval7 — Wed Dec 04, 2019 11:35 pm

Troubleshooting Help • «No device selected», cannot get SDR# to start.

<r>I am having a very hard time getting SDR# to start with a RTL-SDR. I used ZADIG to install the driver. BTW no " Blockusage device 0 was present. Every time I start SDR# I get " No device selected" error. I have included as many screen shots as possible to help with the solution. Thanks in advance for any help.<br/>

<ATTACHMENT filename="ZADIG_2.jpg" index="1"><s>
</e></ATTACHMENT><ATTACHMENT filename="ZADIG_1.jpg" index="2"><s>

<ATTACHMENT filename="SDR#_1.jpg" index="0"><s>


Statistics: Posted by GEMS — Wed Dec 04, 2019 10:35 pm

KerberosSDR • Re: Feedback on possible KerberosSDR V2 Hardware

The Rafael Micro R820T2 chip has been discontinued since march 2018. It will need a replacement. ... -redesign/

--Konrad, WA4OSH

Statistics: Posted by WA4OSH — Wed Dec 04, 2019 9:51 pm

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