Hi, i am very new to SDR and to programming, to get better at both i started working on a code that demoulates FM and AM in cpp. When i demoulate both fm and am from a file, everything works as expected, but when i try and run it in real time i get a lot of noise, i noticed that the noise is created when the lowpass filter is applied to the iq samples. i dont know why it is happening, my programming skills arent great, and i dont know what to do. So if this interests anyone i would love the help because i am stuck and dont know how to continue.
i would appreciate your help,
thanks in advance

As I read, they should be in the L-band around the old PCS frequency range - 1900-1915 MHz; interesting in polarization and setup; maybe some GSM decoders will work on it?

Inspectrum view of a short \"SMS\" packet

Hello, I recently acquired this product: https://ibb.co/hFrkWqL0

It claims to be a 4W radio capable of "SMS" messaging. Unfortunately, the datasheet is incredibly vague about what exactly this protocol is, with the exception of a few things.

1. They call it "SMS" and limit it to a message length of 80 characters
2. It uses CTCSS and CDCSS, 38 and 83 channels respectively
3. Whatever protocol it is, its 1200 baut

I have transmission working, but I've tried decoding it as AX.25, AXFS1200, and some other things, but to no avail. I may have configured it properly for decoding though.

My question is, how can I figure out what protocol this is? Is there any hope? I emailed the manufactures but they don't seem to be responding. I attached an spectrum screenshot of me transmitting a short "AAAABBBBBB" message with the chip.

If it looks familiar to anyone any hints are appreciated. Currently I am frustrated by the fact that I can't tell if I'm failing to decode it because I'm setting up my decoding process wrong, or if I'm decoding it as the wrong protocol.

EDIT:
I believe the transceiver chip used at the heart of the chip is the RDA1846.

Newb here, using SDR++ for a few days now. How do I shrink the upper window so it shows more of the frequency range? I've played with the zoom level, but it won't get smaller... When I installed the program, you could see a much larger portion of the spectrum with the colored "chunks" at the bottom of it, showing the various subdivisions (for example, FM Broadcast, XYZ Ham band)... Not the waterfall area but the one directly above it. I can't for the life of me figure out how to make it bigger or smaller.

https://preview.redd.it/wogit83rm0he1.jpg?width=1260&format=pjpg&auto=webp&s=1bbda8b6759801e38279dad8f3bf667f68bc0bdd

Hi again,
would someone please be so nice and troubleshoot my setup with me? 

I followed the advice and tried APT transmission first.  

But I didn´t get a clean signal while NOAA 15 was passing by, three times in a row now. 

I saw a really weak signal at the waterfall between all the noise, but everytime not at the scoped frequency. I´m kinda aware of the doppler effect, but can´t figure out if thats my problem. 
Changing the gain didn´t do any good, tuning to the probable signal neither.

The last pass at my place was at:

|| || |NOAA 15|Mon, 03 Feb 2025 18:45:27|18:53:01|19:00:36|18:52:54|5.7|67.6|-18|Binoculars|

I was on an open field and due to a satellite spotting app I should got quite some clean line of sight. I held the dipole in hand, facing N/S, about 1m above ground. I tried turning and leveling the dipole to get better reception, but it didn´t work. 

I STRICTLY followed the instructions for building a dipole and especially setting up the SDR++ on https://www.a-centauri.com/articoli/noaa-poes-satellites-reception. 

https://preview.redd.it/hzyv8g0mxyge1.jpg?width=4284&format=pjpg&auto=webp&s=06a155b19eaf79aa7c5aae7f24fd7a081d08e0d0

I´m currently running the setup shown above:
MacBook -> USB-C Extension -> USB-C to USB-A adapter -> Nooelec Smartee XTR -> Sawbird+ Goes (LED is on) -> Balun 1.9 -> copper wires (all SDR parts are stabilized by a stick and electrical tape)

Dipole question:
I cut the length of the wire exactly as shown in the a-centauri link: 54cm till the wire runs into the clamp. In other sources I read about the overall length should be a little bit shorter and that the clamp is included. 

I´m at a quite remote area with bad mobile reception, but somewhat near a big city with an airport.
Do I have a problem with my setup or with my location?

https://preview.redd.it/7n2o4xvbyyge1.png?width=3024&format=png&auto=webp&s=c96aa478c78f2394ce11ef4c49312424f5e75550

I've got a RTL-SDR Blog v4, and I've read that bandwidth affects reception especially on HF bands. I've tried to find some information on this, but I haven't been able to find a good explanation on this. So, my question is, how does the bandwidth affect on HF reception?

If I've understood correctly. smaller bandwidth gets less noise, but is it just as simple as that? Should I just use 250KHz bandwidth, or is there some difference between different bandwidths?

And also, if there's some information explaining this, I would really appreciate it!

Looking to use multiple RTL-SDRs for some ATC monitoring. I realize I could just use multiple dongles, but would nice to just be able to buy an all-in-one enclosed unit to stick in my rack.

The KrakenSDR is more than I'm looking to spend, wondering if anyone has a KerberosSDR laying around that they're not using and might want to sell?

EDIT: Bought one from /u/looongtoez for $100

First of all: I'm newbie. :)

I found a radio broadcast that is clearly some kind of digital signal. I would like to figure it out what it is and decode it, at least until I see a string of numbers.
I'm in Europe, if it's important.

What could this be and how would it be worth starting with it?

https://preview.redd.it/99u2wbg8lxge1.png?width=674&format=png&auto=webp&s=358099c38e66357390f099a9f3a70d3e5878146a

I am taking my first steps into signal decoding.

I have a Nooelec SDR and I am trying to decode the signal from an Ener-J Wireless Kinetic Switch.

According to the datasheet, it uses 433MHz and FSK.

Using the Universal Radio Hacker's Spectrum analyser, I get a pulse around 433.918MHz, but it only appears to have one peak. For FSK I'm expecting to see two frequencies.

I guess the datasheet could be wrong, but I'd wager the mistake is my end.

Is there any way to clean up this signal and see if two peaks resolve?

https://preview.redd.it/wmwoj3ehnwge1.png?width=3002&format=png&auto=webp&s=5d833a49438e60e4ced2a86750502ff565120b35

https://preview.redd.it/qux72nfxrvge1.png?width=1366&format=png&auto=webp&s=267e07654cf0ab5bc1e61cd4b1a42ed1205d3a6b

That is actually 600 bps ACARS being decoded with a passive Diamond MR77B VHF/UHF Magmount antenna with no LNA from Norway with Alphasat at 17° elevation.. Conditions must be very good. Probably about time to buy a lottery ticket.

https://preview.redd.it/xi6sye2ftvge1.png?width=2048&format=png&auto=webp&s=ba8eac95937f9db14ad1d1b362c4bda421d1ed57

Jomjom79

An older thread brings this up in "Figuring out the data transmitted by the Motorola T800"... isn't Motorola required by the FCC to publicly document any digital mode before they can start transmitting? I couldn't find anything, but I don't know how to navigate FCC docs. If anyone knows how to do that, it's this community :)

Hi everyone,

I’m looking for some help regarding the SDR-RTL v4. Is there any software that can perform a full scan of the entire FM band (87-108 MHz) and generate a report containing details for all the radio stations detected? Specifically, I’m looking for a report that includes:

• Station Name
• Program Identification (PID)
• Program Service (PS)
• Signal level in dBµV

The goal is to scan the entire FM spectrum and get a comprehensive list of all the stations it picks up, along with these details. If anyone has experience with this or knows of any software that can do this, I’d really appreciate your advice!

Thanks in advance!

Hello, I am looking into getting into monitoring L Band ACARS, I am not able to install a dish, but I can get away with the RTL- SDR L Band patch antenna.  I have a decently clear shot at the Southern Sky from my home I. The outskirts of  the Washington DC area. my receivers are a RSP Duo and DX receiver, and a couple dongles. I have a few decoding programs MultiPSK and Planeplotter for Areo band decodes.

Here is my question am I wasting my time and money on the RTL Patch antenna? 

https://preview.redd.it/o3cuc089lrge1.png?width=1406&format=png&auto=webp&s=2f6af12e585eccd02f163d6d1fc60da7fce504b1

I'm talking about the random humps. It only appears that this frequency range has it. It sounds like OTH radars, but it's a bit wide for that?

https://preview.redd.it/5usp80xcerge1.png?width=312&format=png&auto=webp&s=29388423ff7016028381c2c3329640ed526d318f

Signal received on 9720khz - 5PM GMT. Can anyone identify this just by eye? Cannot find any matches on Sigidwiki.

Can someone please point me in the direction of some good material on Spyserver. I can’t get it to recognize more than one device. I would like to know more about its capabilities along with how to operate it properly.

Is there any way in GQRX to monitor a larger frequency band by "stringing together" multiple SDRs (i.e., SDR #1 monitors 100-102.4 and SDR #2 monitors 102.4-104.8)? Is there any general-purpose SDR software that supports this, or is there some inherent limitation I'm not considering? I can't imagine it would be a processing issue on the computer end given that there are some SDRs which have 10+ MHz of bandwidth.

Can you import from repeater book into SDR++? I've been trying to convert files and stuff but it is NOT working. I can't find anything online about doing something like this except a python script that errors out on the first line due to format issues or something. I don't understand why this isn't a more asked question/any documentation on it. I would guess it's a common thing!

Thanks all

https://preview.redd.it/4os4ldm10oge1.png?width=1830&format=png&auto=webp&s=dd161a6d344025f86cf13cb94a1804925900414e

5.85MHz seems to be a AM signal, but there are some strong signals around it changing every few seconds. What are them?

Just curious since I haven't seen a image with a resistor not being there.

Does anyone know how to delete entries or otherwise manage the list of url's that build up in the Airspy Server netowrk? I'm referring to these sdr://173.190.0.79:5557/ Thanks in advance.

So i got my self a HackRF One for christmas ! Im into all kinds of tinkering from programming to 3d printers to ethical hacking, arduinos, esp's .. just name it , i probably enjoy it ! ;) So logically i had to get some RF stuff to try :)

I may not live in the best place for playing around with RF, since i live in a small 1500 people town in the middle of nowhere :) But im thinking we still must have some intersting signals or things i could explore with the HackRF One, but uncertain about some things.

First thing that came to mind is the box on my water intake, it has some wireless features and it reports my usage wirelessly (even tough its a bit illegal, i opened the box to see what was inside, but i could not find any sim card or mobile chipset) so i was thinking if it would be possible to find that signal and read it with the hackrf one , or if i would just be wasting time on trying that..

Then there are keyfobs and rf locks, however there is only 1 rf lock in town as far as i know, at least outside.. And my next neighbour is 50m away or some and not often home, so even though those things are cool and maybe i try them someday, i just dont have things to simulate a setup for those things to try here at home.

I thought about trying something like making a gsm basestation at home since i have few old phones and it would not bother any neighbours, same thing with GPS jamming, but im not quite sure about the brodcasting range for the hackrf and i kinda dont wanna try those untill im sure it will not reach my neighbours ( police are no issue, since people would just expect it's me messing around, but i still dont wanna bother people too much with my experiments ;)

However, there is one pretty interesting "target" to explore in town, we are the home base for our costguard (we dont have a navy) and they park their boat here, and im not sure what was from the boat and what was from the surroundings, but with a spectrum analyzer a lot seemed to be going on, and a lot less when the boat was gone few days later.

I just did a quick passive walk by, cause there are a lot of cameras there and im pretty sure it's very illegal if i start probing them activly.. But any ideas if they are brodcasting anything interesting ;) ?

Then we have 3 weather stations and 1 or more earthquake detectors that im pretty sure just brodcast unencrypted data, so im thinking those might be usefull to fetch and use for my home server for my local weather..

However, today in 2025 .. What are people doing interesting with their HackRF One ? And are there any antennas you guys feel are a must have , i only have the one that came in the box

can anyone tell me what are the correct settings to create a movie (video) in wxtoimg i tried several times but its comes out as 0 second videoish file which i cant play.
can anyone give me full settings and how to do it please...

https://preview.redd.it/kz1pu48tmmge1.png?width=408&format=png&auto=webp&s=5249a2aa8a4ccc641075b101097fca0c8196dc7d