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SignalsEverywhere is an amazing community of people who love working with SDR (Software-Defined Radio) and it’s my creative outlet I use to not only teach but also learn from the communtiy togethere.

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Playing Classic Games Over Amateur Radio

Playing Classic Games Over Amateur Radio

About a year ago I purchased 3 NPR-70 Modems. The “New Packet Radio” modem if you will, was developed by Amateur F4HDK and allows you to easily facilitate TCP/IP communications over Amateur Radio with options for various speeds. While the modems are capable of 500kbps due to CFR 47 Part 97.3 FCC regulations in the United States we are limited to 100kHz and 56kBaud. Thus putting our speeds closer to 65kbps.

Still, 65kbps is nothing to sneeze at when your options for TCP/IP communications over Amateur Radio have been limited to packing up AFSK AX.25 frames over 1200/9600 baud connections or having to setup point to point links. Up until now there really hasn’t been many options to do this.

So, what can you do with 65kbps? Why not try to play some classic video games?

I tested this out with Unreal Tournament 99 Demo, Unreal Tournament 2004 and OpenRA an open version of WestWood’s RedAlert series. UT99 and OpenRA did the best at around 100ms ping times throughout gameplay while UT2K4 gave an average of 201ms ping. Still, these are perfectly playable (especially if you grew up in the land of dial-up internet)

So, how do we get this all set up?

Essentially you need to have a router and two NPR modem’s to pull this off, for my experiment I just used the router on my home network and disabled DHCP on my Modem’s to ensure that I couldn’t resolve domain names thus making it a bit easier to connect to the services I wanted to without clogging up the works too much, although yes… A dedicated router would be best.

When connected via USB you’ll be presented with a serial interface at 921600baud. Connect an NPR-70 modem to your computer via usb and to your router via ethernet and connect to your serial interface.

You’ll want to adjust these values to match your subnet but essentially it goes like this.

set frequency 433.500
set modulation 20
set RF_Power 7

set callsign yourcall_0
set is_master yes
set DHCP_active no
set telnet_active no

set def_route_active yes
set DNS_active no
set modem_IP
set IP_begin
set master_IP_size 29
set netmask


Then for your client, do the following.

set frequency 433.500
set modulation 20
set RF_power 7

set callsign yourcall_1
set is_master no
set DHCP_active yes
set telnet_active no


Once everything has a few moments to connect you can use the “who” command on either NPR-70 modem to see if they are connection to each other properly, if so you should then be able to ping the master or any other IP on the subnet from your client computer.

Now you should essentially be able to set up any TCP/IP client/server application you wish. Including some classic video games!

Unreal Tournament ’99 Demo on 433.500MHz

NPR-70 Modem communication

More details on these can be found here:

Remote SDR The Pi Transceiver

Remote SDR The Pi Transceiver

André, Callsign F1ATB has released a project they call “Remote SDR”. Originally developed for operators of the QO-100 satellite Remote SDR using a Raspberry Pi and a couple of SDRs provides you with a full blown transceiver in your web browser.

Released as a series of Raspberry Pi images on GitHub Remote SDR allows you to connect two SDRs to your Raspberry Pi such as an RTL-SDR, PlutoSDR or HackRF as well as SA818 modules in order to provide you with both remote transmit and remote receive capability in a convenient web-based user interface.

Depending on the Software-Defined radios you choose to use with this project will determine your available operating frequency range anywhere from 1Mhz to 6Ghz. While there are other modes still in development NFM and SSB are the primary modes you’ll have access to with the current release as of the date of this post. This project also has an interface option for gPredict which would allow you to automatically account for Doppler shift during Low Earth Orbiting satellite passes.

The project page provides several examples of various configurations with QO-100 operation in mind and consider the HackRF provided the external TCXO is installed; has the best frequency range and frequency stability.

There are various configurations available depending on the SDRs you have on hand and what your intention is with them. The Full-Duplex nature of the PlutoSDR would make it the simplest of the examples provided as you need only one SDR connected. Please keep in mind that if you plan to use an SDR on the air as a transceiver you must ensure you’re properly filtering your output and are licensed to operate on the given band you are transmitting on.

An Open Source P25 Scanner Control Head!

An Open Source P25 Scanner Control Head!

December 26th 2018, that’s when the Signals Everywhere community and Myself decided to start working on a project we called “Pi25”. The idea was simple, take off the shelf hardware and use it to create the first open source portable digital radio scanner!

Well, while simple in concept actually getting the parts we needed, learning hardware and software as well as having the funds to buy hardware to work with slowed us down. I had started doing some basic 3D modeling to get an idea of where the project might be headed.

By March of 2019 I had finally started working on getting data from OP25 to display on an OLED screen.

Demo Video of OP25 Data Display

That’s about where the development ended until January.
See there were two designs for the Pi25 project, the first was a hand-held portable unit designed specifically to replace your traditional portable scanner.
The second was intended to be a mobile scanner that you would use in your vehicle.

The First Revision wasn’t Great :/
Development was progressing however!

This is the point in the project where I started making some big changes. I went from attempting to re-design the horrid web-ui with another horrid web-ui to writing my own UI in python. The idea here was that the Rasberry Pi would run not only the OP25 software but also the display. It went through several variations from here.

You could see progress slowly being made here.

This was the point in my project that I realized I could begin to add my own features on top of OP25, this didn’t have to be just some passive overlay to the WebUI provided with the software, this could manipulate the OP25 instance to do things nothing publicly available could do!

Suddenly my UI could auto-connect to an OP25 instance, it supported Radio Reference database importing and more.

With the new remote application on the Raspberry Pi with the OP25 instance I could now start doing things like importing Radio Reference data and implementing my own modes of functionality.

I added night-mode functionality that would auto-switch depending on the time, an alert window which would read a file and provide you with an audible, visual and logged alert when that talkgroup was heard.

The ScanGrid

After suggested by a viewer I began working on the scan grid. This feature was completed on January 20th and would allow you to create a grid of buttons to enable/disable the scanning of talk groups on the fly. This meant that you could easily modify your scanlist without having to sit in a text editor or go through a bunch of menus when you’re on the go.

Site Location Tracking and Auto-Site Switching / Roaming Completed!

By the end of the month this revision was nearly completed and I had successfully tested automatic site-switching which allows you to drive through an area and have OP25 automatically switch sites based on your location in relation to the known tower location we grabbed from our radio reference import.

I of course had to figure out how to plot those sites on a map first.

The only downside to what appeared to be a very successful software release was that the application ran poorly on the python interpreters available for Android and it was very limited when it came to grabbing system calls (or using an actual cell-phone gps and not just the usb model I had).

This meant that once again I was going to have to re-write this thing in order to make it useful as a mobile control head. The fact that I would deploy to android and potentially iOS also meant that nearly any mobile device could become the GPS unit and the touchscreen display for the control head.

I decided I was going to write this in Kivy allowing me to easily port to Android/iOS without drastic changes to the updating code I wrote for use on the back-end.
About 5 days later on February 2nd 2021 I finally had the webUI text updating on the App in real-time
A few more days and I had some basic talk group information displayed.
Shortly after figuring out how to get my text to update I started framing the App in a similar fashion to that of TKinter.
This too was re-designed as I put everything into a proper Material Design menu and begun to re-implement my call log

Finally at the end of March I have an APK compiled and running on my phone!
There is so much that went into learning how Kivy works to get this moving, not to mention manipulating OP25.
I have a heck of a lot more left to implement, design and re-design but I hope one day I’ll have this sitting in my car replacing the $1000+ scanner and put it up on the app store so others can do the same.

Below is the current state of the App, to be released once I hit Stable Alpha 1.0

I’m Transgender

I’m Transgender

This community is hands down one of the greatest things I’ve ever had the pleasure of being a part of. I love sharing my knowledge with others and more importantly learning for the community as a whole.

Many of you have noticed that content has been flowing at a very very slow pace, there are a few reasons for this one of the biggest is actually that I’ve been trying to move for some time.

There’s another reason and you’ve likely already guessed either due to the title of this post or the fact that you likely have noticed that my Avatar has changed on the website, YouTube channel, Discord and even my Twitter account.

So it’s finally time to say it, I’m transgender and I’m working on becoming my true self.
Signals Everywhere isn’t going anywhere and the content isn’t changing.

What is changing is that I’m a proud Trans-woman and I will be using the name Sarah Rose from this point on instead of Corrosive or the name that shall not be mentioned. I thank all of you for your support and hope to get things moving in the community and on the channel once again!

Discord APRS/License Verification

Discord APRS/License Verification

Recently we’ve had the pleasure of being able to add a number of new features to the Discord bot known to the community as “Grant”. This bot handles a number of tasks not currently found in other bots.

I used to write these in Python however, a community member [xX_WhatsTheGeek_Xx] already had a bot framework he built using Node.js called [Oxyde] (which despite my previous distaste for the language I’m learning to love it)

He has taken over bot development on the server and I couldn’t be happier with the results, while I play with Python mostly for my own enjoyment it goes to show how quickly things can be implemented when you have someone who better understands the language working on it.

One of the biggest features of the bot is an APRS message gateway, this is a bi-directional gateway which allows members of the server to send and receive APRS messages from within Discord. However, this bot does allow you to traverse the RF side of the network as well.

Thus I legally take the burden of ensuring proper use of the service who is operating it via my call callsign K8SDR.

There is now a role called “Verified Ham” which is used to stipulate which users are allowed to access this feature (and up-coming RF features)

In order to help ease the process of verifying legal operators you can now send a DM message to our @Grant bot with the word “verify” and an image of your license.

User sending an approval request

The image and user details are then send to a hidden Administration channel were we can quickly approve or deny the request and the bot will automate role allocation and notifying you of the decision.

Verification as seen by Administrators
Role approval notification

If you’d like to play with these features, such as APRS check us out on [Discord]

A member sending a message from the club callsign with my approval
Ethics in the SDR Community

Ethics in the SDR Community

Software-Defined Radio, SDR and the great responsibility that it comes with.

We’re currently in a radio renaissance comparable with the days of the blue box or the 56k modem we’re in an era where radio has been blown wide open and made available to anyone and everyone who might have any interest in it.

I’ve seen so many amazing uses of this technology and for many it has opened new doors into a world that they didn’t know even existed. There is something amazingly luring about knowing what a satellite transponder looks like or being able to decode pager messages.

I’d like to take a look back throughout history, the moment people started hacking the phone system for free long distance calls, the explosion of the internet and how quickly many used it for illicit purposes, something used today by the government to begin restricting what we can do online.

Among many enthusiasts of Software-Defined Radio is the cyber security community, and why wouldn’t they be? Radio in many aspects has always followed the “Security through obscurity” model which…. I’ll give you a hint. Isn’t a very good method of securing anything.

Why was this though? Frankly I attribute most of this to the fact that most people couldn’t afford a decent radio scanner and even if they could it likely had areas blocked or required a lot of modification to do anything outside of passive listening. There wasn’t much incentive to encrypt communications that many had no way of monitoring in the first place and so they didn’t.

Now we’re at a stage where security researchers and even your every day hobbyists are blowing things wide open because we went from needing thousands of dollars in equipment to for around $300 you can run a cell site inside your own home! The move to software-defined instead of the old hardware-defined has truly unshackled us all from what we once thought was possible.

Where I ask however, is the limit?

We can monitor pager traffic, decode satellite voice communications, jam GPS and so much more (nothing I condone ofc) The problem I am seeing more and more frequently is that many beginners are hopping on the band wagon of decoding and sharing phone calls, pager messages and other private information with the general public. This is a crime in the vast majority of countries.

Consider this, legal or not.
You are monitoring Iridium or Inmarsat and hear a call come in, most of these calls especially on Inmarsat are calls between emergency Medical personal to those on aircraft dealing with a life threatening situation. Do you really want to listen to someone on the phone explaining how their loved one is dying on a plane and there is little that can be done to save them?

Let’s take another example from pager decoders, most of the paging systems still active (in the United States anyway) are in operation exclusively for hospitals. The vast majority of pages contain confidential information such as patient details and more. Do you really want to know that someone by such and such a name is having a heart attack and they just called a whole floor to the operating room?

I want to have a real discussion about ethics here because while there is something to be said about the legality of some of the things we do and how lawmakers might look at our hobby in the future. We also have to realize like many have though out history that sometimes we think we’re just sitting behind a keyboard having fun when….. sometimes we’re somehow excitedly looking at something that while interesting to us is probably the worst day of another’s life.

Next time you’re thinking about playing with a transmitter, consider power output and license requirements, there is a good reason for it. It’s not that hard to even accidentally disrupt communications. I really want people to think about what it is they are doing. Just because you have the capability to do all these things doesn’t mean that you should.

We all love this technology and I’m sure we all want it to continue to be as un-impeded as possible, part of that is making sure we’re taking the steps not to abuse this new power. To some, this is a super power. It’s an ability that most don’t wield and frankly it’s a new ability to nearly all of us. Don’t abuse it.

The Winds of Change

Yes, I know things have been slow as of late. Let’s get right down to it.

Many of you may have noticed a change in the frequency of YouTube uploads, Blog Articles, and even Podcast episodes. Even social media was suffering, my Twitter, Facebook you name it!

So, why is that? Well, that’s a long story but to get right to it maybe it wasn’t all bad and I think it will prove to be a great thing in the long run.

There were some things going on in my personal life and between that, work, family and everything else going on.. Not to mention the four or five projects I had been planning and several videos I owe people that I’m still trying to finish!

So, due to this personal stuff, I missed an episode… after that, I took a break.
I love making videos but I needed to figure things out. There was just too much to do and far to little time.

Currently, I’m in the process of delegating some sections of Signals Everywhere to various community members. This means we have some amazing people helping out, whom you can see on our new “About Us” page.

I’ll be making some more announcements soon but I hope that with others taking on some of the work that I have been doing by myself is actually saving the channel.

With these things somewhat off my mind, it’ll give me more time to work on my video content and connecting with the community rather than maxing myself out trying to do it all.

Thank you all for your time, have a great day!
I can’t wait to see where we go as a community.

NOAA 15 Experiencing a Failure?

NOAA 15 Experiencing a Failure?

This isn’t the first time we’ve seen issues with the NOAA-15 satellite. Last year the RTL-SDR blog posted about some issues the satellite was having.

These issues/errors appear to have been intermittent and even today these problems while apparent haven’t been constant. However, they do appear to be happening more and more frequently. There is a bit of uncertainly in the air about how much longer we’ll have this satellite and other which hold easily obtainable APT data.

We can only hope that this is just another intermittent problem but alas it seems like NOAA-15s clock is just about at its end.

MiTEE Cubesat Interview

Hi, Derek here with a few addenda to the video here.

I want to clarify that everything said here was my opinion and not necessarily representative of the University of Michigan or even MiTEE as an organization.

The CubeSat was not at all completely designed by students on an electrical level. I misspoke and didn’t realize that mistake until after editing. We received major help from the Space Physics Research Laboratory (SPRL) on campus here by adopting some of their electronics from a previous CubeSat mission they ran. Overall about 50% of the electrical design work though was completely lead by the students here.

Check out our twitter page at to stay up to date with the latest mission activities regarding our launch!
Finally, I want to give a huge shoutout to SPRL and Prof. Brian Gilchirst for all of their help in making this project possible for the countless number of students that have been involved. Without their knowledge and material resources, we would never have been able to get to a point where we are awaiting a final launch date to get into space.

Well, one more I guess. I’m a rising junior in electrical engineering and I’m actively looking for an internship for the summer of 2020. So if you enjoyed my semi-educational talk about students in the CubeSat world and didn’t catch my numerous mistakes regarding design and testing paradigms. If you might know of somewhere I should apply or want to contact me for further questions here’s my LinkedIn and my email is cheyndk@umich dot edu

Guest on Signals and Bits

I was recently interviewed on a new podcast [Signals and Bits] created by Ben Hilburn [@bhilburn]. Ben has been an influential individual within the radio and open source software community for many years. He is the President of the [GNURadio Project] that has no-doubt been at the core of the Software-Defined Radio community before anyone even knew what RTL (SDR) was. He also works on a multitude of other projects you can find on his [website].

Ben’s podcast will be in an interview style focusing not only around Software-Defined Radio but topics such as spectrum enforcement, consumer wireless, AI and much more. You’ll no doubt enjoy this episode and the many to follow. Please be sure to share feedback with Ben on twitter [@signalsandbits]