Why Can't I Grasp This?!?

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BigNutz
Posts: 5
Joined: Wed Mar 03, 2021 11:06 am

Why Can't I Grasp This?!?

Post by BigNutz » Wed Mar 03, 2021 12:14 pm

Hey Everyone:

Long time lurker, finally gave in to my reality and registered for an account. I'm not sure what or where my disconnect is with this discipline. I have a relatively solid understanding of RF theory, grew up in a house with a father who has just retired after a brief 43 year stint as the local NBC affiliate Chief Audio Engineer & Voice Over Announcer. He also built and ran his own unlicensed low power AM radio station in his basement when he was 11, so I'm sure most people here can imagine the kind of guy my dad is.

Anyway, instead of audio engineering which required algebra and logarithms to master, my industry of choice was civil aviation. Yes, I'm a licensed commercial pilot, but flying was a brief minor path I thought was right for me, until I realized it wasn't. Unlike most aviation industry careerists, I bounced around the industry always ending up in some obscure sector which was in no way related to the sector I had previously came from. Wasn't a planned strategy by any measure, I just jumped positions every 2½ years or so, out of jobs that are usually filled for careers, eventually finding my place in the world as a USAF Civilian Intelligence Officer and Civil Aviation Subject Matter Expert (SME).

I spent 8 unbelievably glorious years proving to everyone around me, and eventually to myself as well that it is absolutely possible for someone to love a job too much. Sounds counter intuitive, I know, but trust me. Anyway, this was the first position I had held where I actually used absolutely every obscure drop of industry experience and knowledge I had gained prior to being hired. I also was compelled to learn more about the theory underlying and operational understanding of the ADS-B system. So, now I am doing what Iu used to for the USAF, only through my own company and in controlled doses.

Now I am being asked to spend some money to determine which combination of COTS components provides the best balance of reliability, signal acquisition performance, cost effectivness, and then be packaged in a sealed enclosure which is as understated and visually unappealing as possible. So, I'm now in the component selection confirmation period where I will scrutinize the selections made to ensure nothing was missed. After that, I get to break stuff, everyone's favorite part of any hardware development project, austere condition stress testing. I have two beta articles which represent the likely release for deployment builds we'll use assuming the components continue to play nice together at 140°F for a couple hours. To up the probability of success, we've included a full submersion of all components within the enclosure using thermally conductive potting compound, which to date has never failed me.

So what can't I figure out? Why am I here writing this book? I'm here because I'm sick of having to rely on the SDR manufacturers to provide me with SDR units which have been preprogrammed prior to shipment to the 1090MHz that I need. I actually have a number of RTL-SDR v3s that I would like to set the frequencies for. I also have some Nooelec Nano 3 SDRs (which one could heat their apartment with buy simply plugging in), and a few other less respectable brands.

No matter where I look on the SDR websites, I cannot for the life of me find an explanation which says "Use this Software, plug it in, click this menu, type in 1090MHz, push saves, done"

I've started to think that they actually aren't programmed at all, and the frequency selection to 1090MHz is executed by the Dump1090 or PiAware software running on whatever type of processor setup being used. I can't believe the manufacturers would bamboozle people by selling standard SDRs as pre-tuned to a specific frequency knowing that the software will make it look like they weren't involved in such tomfoolery.

The other possibility is I'm simply not savvy with respect to the SDR Community's vernacular, and am misreading the guidance I'm looking for when it's literally right in front of me. So let me drop some terms that might be messing me up.

Is setting an SDR frequency referred to as "frequency calibration"?

Do SDR nerds refer to an SDR module or dongle as a "Rig"? Seems a touch on the hyperbolic side, but if that's what you guys call it, I'll call the damn things a rig too. I usually associate that term with 14 ton semi being driven 95MPH down an icy secondary road... THAT'S a rig!

Anyway, I'm hoping this will be an easy reply for someone. I asked on Stack Exchange, and recieved a very pleasant reply from someone who really took some time to try and educate me on how to tune these, but he grossly over estimated my computer programming capabilities and could have been describing this process in Kingon as far as I could tell. He was talking about a quick line of code -----

Please note, and I should have lead with this with that guy, the instant someone starts explaining to me how easy it is with a simple line of code, programming, or anything related, I have no idea what's going on. I don't even know where people type this code, in Microsoft Word? Google?

Now, if you lay out a detailed 5 year old level set of plain language instructions, being careful not to assume I will understand programming shorthand or how code is entered into the computers, we may have a chance.

I appreciate anyone and everyone who commits to this challenge, and I will repay that person with enough ADS-B operational theory and practical applications, you'll want to make an SDR reciever too!

Thanks,

BN

majicm
Posts: 4
Joined: Sun Feb 28, 2021 12:09 pm

Re: Why Can't I Grasp This?!?

Post by majicm » Wed Mar 03, 2021 5:37 pm

SDR unit's aren't "pre-programmed", they are just receivers.

The software is the interface for you use to control the receiver. There's no writing of any code, no more than you would to stick a mouse dongle in your PC or laptop.

What software are you using?

You plug the device in, load up SDR # and start the device. Then tune to 1090.

It sounds like you're trying to deliberately make it sound more complicated than it is, talking about writing lines of code or radios being pre-programmed.

What exact steps are you taking to try and get this working?

BigNutz
Posts: 5
Joined: Wed Mar 03, 2021 11:06 am

Re: Why Can't I Grasp This?!?

Post by BigNutz » Thu Mar 04, 2021 10:32 am

Finally! A reply that makes sense!

Thank you for replying, I'm going to answer all your questions and then ask more.

I tried 4 or 5 of the different free software options, I know one was SDRSharp, the Zadig option, Cubic SDR, and one which started with an "M" which I can't seem to find. One of them upset my laptop and was preventing MS Word from loading and just throwing an error code. No MS Word, no worky, no worky, no money. Suffice to say, I didn't have time to figure out which one was causing the issue so just uninstalled them all.

So, I'm tracking what you're saying about firing the SDR up with one of those programs and easily tuning 1090MHz, which I successfully did with each different program. The issue is the SDRs are going to be running on the laptop or with any of those programs. I'm building a stand-alone, Raspberry Pi 4 based self contained receiver which are intended to run free of any required intervention, and piping all the flight track data acquired up to a cloud-based storage server to be used as historic look-back analytics to contribute to a larger effort focused on the characterization of air traffic patterns in a given volume of airspace or IVO a specific airfield.

You're the first person who has told me that these SDRs are incapable of being tuned to a specific frequency and configured to retain that frequency if the SDR is deactivated and power supply removed. I suspected that this might be what was happening, and would suggest that with my application described above that the Dump1090 software running on the Raspberry Pi is the mechanism by which the SDR is set to 1090MHz. Is that accurate?

So when I order the Noolec Stratux ADS-B Bundle: Dual-Band NESDR Nano 3 bundled kit, which their website lists that it: "Includes 2 calibrated and programmed NESDR Nano 3 SDRs", and when the package arrives with the two Nano 3 SDRs packaged separately and are labeled "1090MHz" and "978MHz", these guys are blowing smoke up my skirt???

If you're reading my questions as challenges to your claims, I am not. I wonder if these companies are adding integrated 1090MHz centered LNA filters and calling them "Programmed". Who knows, I'm just glad someone finally set me straight. Thanks again for taking the time the to unscrew myself. I'll drop the link below so you can see how these guys are framing their SDRs.

Pete

https://www.nooelec.com/store/sdr/sdr-b ... ano-2.html

https://www.nooelec.com/store/stratux-b ... ano-3.html

BigNutz
Posts: 5
Joined: Wed Mar 03, 2021 11:06 am

Re: Why Can't I Grasp This?!?

Post by BigNutz » Thu Mar 04, 2021 1:12 pm

And the hole they are digging apparently gets deeper. Check out the statement on their SDR brand description page! I need to hit these guys up and get some clarification as to what this "tuner chip" they keep referencing is all about. At least I can show where all my confusion is stemming from.


Image


And now I see this in their Q&A section..... I feel like I've been misled and lied to, I'm still asking.

Q: I bought the Stratux bundle, but I want to tune in to frequencies other than ADS-B. Do I need to buy another SDR?

A: No, there is no hardware difference in the SDRs in the Stratux bundle. You can use them to tune into any frequency between 25 MHZ and 1700 MHz. Just make sure that you are using the appropriate antenna for your desired frequency!

hotpaw2
Posts: 180
Joined: Sat Jan 14, 2017 11:07 pm
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Re: Why Can't I Grasp This?!?

Post by hotpaw2 » Thu Mar 04, 2021 6:37 pm

The RTL-SDR operating receive frequency has to be set by software. That receive frequency is not stored in the RTL-SDR when power is removed, but has to be set by software each time the unit is started.

However, some RTL-SDR units have a band-pass filter in front of the tuner, set to certain aviation bands. Those front-end band-pass filters are built for specific frequency bands, but the R820T tuner behind the filter still needs to be set to that frequency by software.

So you may need both an RTL-SDR with a filter set for your frequencies of interest (if you want to eliminate potential interference from frequencies outside the pre-filtered bands), and software that will set the RTL-SDR to that same frequency band when the unit is started up.

majicm
Posts: 4
Joined: Sun Feb 28, 2021 12:09 pm

Re: Why Can't I Grasp This?!?

Post by majicm » Thu Mar 04, 2021 8:13 pm

BigNutz wrote:
Thu Mar 04, 2021 10:32 am
Finally! A reply that makes sense!

Thank you for replying, I'm going to answer all your questions and then ask more.
So, in all honesty, I can't vouch for the ADSB receivers as I've never seen / used one. I've always used RTL-SDR and then moved onto RSP2 Pro and then an AirSpy Mini. The ones specifically for ADSB may have their tuner set to a restricted frequency, I really don't know. However, if you're just using a simple RTL-SDR then that has a frequency range of between 25 Mhz and 1.3 Ghz I think.


So, the software you use is what tunes the frequency on the radio. So SDR Sharp is what I use, that connects to my Airspy and I tune the frequency in the software.

I've recently changed my setup (due to a house move) and now my Airspy is sat connected to a Raspberry Pi 400 running SpyServer. I think connect to the Pi over the network and I control the Airspy via SDR Sharp.

You shouldn't need anything more than you already have, the standard RTL-SDR should cover everything you want - the fact the No-Elec says it has the "RTL2832U tuner" should be all you need, it has the range I mentioned previously.

BigNutz
Posts: 5
Joined: Wed Mar 03, 2021 11:06 am

Re: Why Can't I Grasp This?!?

Post by BigNutz » Thu Mar 04, 2021 8:45 pm

Awesome....Just awesome...

Again, I appreciate all the information. I'm, serious when I say this, I've probably at a minimum tripled the sum total knowledge regarding SDR's and the ADS-B receivers from just 24 hours ago. All the ADS-B system understanding and expertise is great, but now I have a FAR better conceptual grasp on how the sausage is made once that little flight track data packet gets scooped up by the antenna and sent on it's journey to live in a cloud server forever..

So, like a pigeon or a change seeking homeless dude, you dun fed me, and now I know where the vittles are. And by vittles, I of course mean your smartness. Can you explain to me what the roll of this mysterious RTL2832U Demodulator plays, why it's frequently associated with USB 2.0, and where is sits in the hierarchy of SDR stuff in terms of it's performance when compared to other versions of what it does?

Lemme guess because you'll tell me if I'm wrong again, so no risk of that fiasco last night.

Based on my Tom Brady level analytical prowess, I assess that the RTL2832U Demodulator is associated with it's friend with benefits, USB 2.0 because it acts as the air traffic controller of ADS-B data. It receives what is raw and likely dirty/ impure data from the tuner chip (assuming the tuner chip ever even touches the data. It could simply take the instructions from the big baws man, Dump1090, set the dial, and call it a day) and somehow pre-processes it in the simplest of terms, and then manages the throughput flow using that USB 2.0 buddy, and all or some if what I pulled out my stink-star is considered the task of demodulating.

How'd I do? Should I just stop trying to guess at these things. Gee, it's too bad there wasn't some website or something that has an entire library of helpful information just like this..Huh?

I am digging through that stuff as well. The problem I am having is that the resources aren't stored or presented in a tiered fashion. What that means is if I start reading one of the blogs reports, and quickly realize the author was referencing SDR vernacular that means nothing to me because he wrote it for blokes like you, there are online resources like that which tier the content so you can drill down a level if something is above your level of understanding. Drill down and down until you get to the level where the content is delivered at a basic fundamental level, all acronyms and distinct concepts are explained. This site isn't structured like that, and I spent an hour this morning just trying to find a basic explanation of what PPM stood for, which I eventually learned was exactly what I had thought it meant, which confused me even more. The PPM measurements I know about are measuring doo doo particles floating in the air when you crop dust someone. How in the hell that metric was being applied to the known range of frequency drift allowed by that crystal thing with 4 letter acronym still makes no sense, even after I read an explanation of it. Anyhoo, that's why I'm going to be the neighbor you learn to avoid at picnics because he just WON'T STOP TALKING.....

Thanks in advance, and may God have Mercy on your soul...

BN

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