Архив за 13.09.2019

How can I determine whether a signal is P25 Phase 1 or Phase 2? Is this a P25 signal? (link)

I just received my RTL-SDR and am running Airspy V1.0.0.1715 and DSD+ 1.101pt. I tried tuning to my listed local PD dispatch frequency, which went over to digital years ago. I can hear occasional buzzing signals and can see the the DSD+ Source Audio window filling up with waves, but there is no activity at all in the DSD+ event log or the status window. It is not decoding anything or even indicating anything is happening.

I'm now wondering if this might be Phase 2. I don't know how to tell the difference and I don't want to start installing Linux if there is just a simple oversight.

The problem is I can't figure out how to tell if this is Phase 2! I checked sigidwiki.com and of all things, Phase 2 is completely overlooked, so there's nothing to compare this signal to. I did play some of the wiki's Phase 1 samples through my speaker and by accident I saw that DSD+ responded to those. It doesn't respond to the playback of my own recorded signals though.

The RadioReference guide in my area is extremely incomplete but a local radio amateur confirmed the system here is P25 but doesn't know which phase.

Audio sample: https://pixeldrain.com/u/W9VEgVd-

Waterfall/program appearance: https://i.imgur.com/sYdz68w.jpg

I'm hoping someone can put me on the right track. Is my signal too weak? Any idea what this transmission is? Or if I need to be looking at other frequencies?

submitted by /u/3DHouseOfBeef
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User Projects • Re: SDR Math, Back to School

From an early age I was very interested in learning mathematics. Along with studying, I used to practice mathematics. I want to learn SDR Math now. Thank you so much for your article.

Statistics: Posted by DannyMauro77 — Fri Sep 13, 2019 4:51 pm

User Projects • Re: Absolute FFT Beginner Project

I'm really surprised to see your interest. Really, I can't think that you are a beginner. Stay tuned you can do something good. I'm a web programmer. I have almost 2 years of experience working with Python. If you need any help then let me know.

Statistics: Posted by DannyMauro77 — Fri Sep 13, 2019 4:46 pm

KerberosSDR • Re: run it on rpi4

Hi everyone,

I've done all these steps and am able to run the app on my pi4, but I can't get it to do anything. I Click Start Processing and I get no updates. I get no errors when uncommenting the logging in the run.sh either. rtl_test works on all the devices (at least I think, the output is below).

What else can I try?

Output from rtl_test:


pi@raspberrypi:~ $ rtl_test -d 0Found 4 device(s):  0:  RTL-SDR, KerberosSDR, SN: 001  1:  RTL-SDR, KerberosSDR, SN: 002  2:  RTL-SDR, KerberosSDR, SN: 003  3:  RTL-SDR, KerberosSDR, SN: 004Using device 0: Generic RTL2832U OEMFound Rafael Micro R820T tunerSupported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6[R82XX] PLL not locked!Sampling at 2048000 S/s.Info: This tool will continuously read from the device, and report ifsamples get lost. If you observe no further output, everything is fine.Reading samples in async mode...Allocating 15 zero-copy bufferslost at least 832 byteslost at least 1032 byteslost at least 580 byteslost at least 226 byteslost at least 1966 byteslost at least 2124 byteslost at least 934 byteslost at least 226 byteslost at least 934 byteslost at least 1288 byteslost at least 226 bytesno more output after this...
I'm using a 3A power supply for the PI and I have just one micro-usb from the USB3 port on the pi to the KereberosSDR. Do I need a second power supply for the KSDR?

Statistics: Posted by serff — Fri Sep 13, 2019 4:37 pm

KerberosSDR • Re: Feature requests / development ideas

Kerberos designers can correct me if I am wrong but if I got it right this is not like a power vs frequency calibration that you put in a table and update once in a while when some external condition (temperature...) changes. The 4 receivers have a common clock so they are coherent at a certain point in time but as they are 4 independent receivers otherwise using each its own USB channel you don't know that certain point in advance yet it will not vary as long as you keep the USB link alive and some other receiver parameters like center frequency, gain, sample rate (afaik). Therefore you cannot have it in a static table that you change every so often you need to run through a calibration cycle at every power up and parameters change.

Some MIMO devices (MI for Rx part that is) like LimeSDR, BladeRF v2, XTRX... do not have this issue because the two (don't know of more than two) receivers live on the same chip so their time difference is constant by construction and can be corrected (or made null in the chip fabric) once and for all. But they don't sit in the same price range and I don't know of any with more than two receivers.

Statistics: Posted by f4exb — Fri Sep 13, 2019 3:07 pm

RTL-SDR Discussion • Re: Kali Linux 2019 and Bias-T

Since Kali is debian based, it may be the same issue that I am seeing on my SatNogs station (Raspbian). Apparently the bias-t switch only works with with certain libraries (as rtlsdrblog has mentioned). If your Kali version is based on debian buster, then it should work. If not, you'll need to do some package updating. Unfortunately that's about the extent of my knowledge.

You can see more about this in the troubleshooting forum, under the thread about the bias-t and SatNogs.


Statistics: Posted by K3RLD — Fri Sep 13, 2019 1:28 pm

RTL-SDR Discussion • Re: Listening to AM radio

This one doesn't support frequencies below 24 MHz. You're needs RTLSDRv3.

But this blue also can be modified in order to use frequencies below 24 MHz, but it's not easy and it will be much more easy to buy RTLSDRv3 which support it out of the box.

Statistics: Posted by radiolistener — Fri Sep 13, 2019 12:15 pm

RTL-SDR Discussion • Re: Listening to AM radio

I've attached a photo. Looks like this device probably can't do AM frequencies.

Statistics: Posted by LogicalUnit — Fri Sep 13, 2019 10:51 am

RTL-SDR Discussion • Re: Listening to AM radio

It depends on what exactly a "sky-blue 820T2 & SDR module" is.
Is it advertised as doing direct sampling? Does it have an upconverter? Ordinary RTL modules go from 24MHz upwards.

Statistics: Posted by alanzfq — Fri Sep 13, 2019 10:03 am

RTL-SDR Discussion • Listening to AM radio

Hi guys, I'm sure this is a very noob question. I tried searching, but all my terms were too common.

I've got my sky-blue 820T2 & SDR module installed and working (shows up as RTL2838UHIDIR in Windows device manager), and I'm happily listening to my local FM radio stations in SDRSharp. I would like to listen to AM radio, specifically a station that broadcasts on 666 khz (Canberra ABC). I've set the radio button in the radio panel to AM and tuned to 666,000 but I'm only getting static. Is my module capable of receiving this frequency, and what settings do I need for it?


Statistics: Posted by LogicalUnit — Fri Sep 13, 2019 9:14 am

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