Railfan Technology > NXDN update.

I made my annual trip to the Dayton Hamvention this past weekend. It’s the world’s largest ham radio gathering. Besides a large flea market, there are representatives from several manufacturers including Kenwood, Icom, Yeasu, and others. I talked to some of the reps about the future and NXDN scanners and receivers. The Kenwood rep was the most knowledgeable. I ask about NXDN and he knew exactly what I was talking about. Told him I was a railfan and he immediately told me about the software update he had just completed for BNSF. He talked about AAR, FRA, Clean cab, and other things as routinely as your mother would have told you to eat your peas and carrots. As far as railroads converting to NXDN he said that as of now, several roads are using it in the yards but very few are using it on the roads at this time. He said that Canadian railroads were using it on the road more than the U. S. railroads.

Bottom line was that Kenwood didn’t have anything in the mill to produce a consumer grade scanner or receiver and he didn’t think any of the other companies had anything either. I confirmed that with Yeasu and Icom. They were not as knowledgeable but they knew what I was talking about.

One thing that I did find was that AOR, the maker of some high end scanners has a product that they have recently released that will decode NXDN. That was the good news. The bad news is that it is an adapter that uses the 10.7MHz I.F. (Intermediate Frequency) from an analog scanner. Most, but not all scanners probably use the standard 10.7 MHz I.F. but you would have to go into your scanner and modify it so that you could access the signal. AOR has an I.F. output on most of their scanners / receivers. The only problem is they start around $800. The Adapter also cost about $800. BTW, some of their radios get into the thousands. Did I mention that they were high end?

So the bottom line here seems to be, there doesn’t seem to be any consumer grade (under $200) scanners capable of decoding NXDN at this time. There are some costlier options available and there are commercial grade radios available. The good news is that at least someone (AOR) has made an adapter. It’s expensive but it a first step in the monitor world.

There is one other option that I have discovered. It’s the SDR, or the Software Defined Radio. It’s usually a small device that interfaces with your computer via the USB port. You have to use the computer to control the frequency, volume, and the decoding of all signals. The software is free but it takes a bit of work to configure it. It’s not a task for the technology squeamish. I have an SDR in the form of a “dongle.” One end plugs directly into the computer and an antenna goes on the other end (see the photo below.) Basically you have a program to control the radio (SDR device) and then additional plug-in software to decode NXDN. The SDR type radios cost between $35.00 to $200.00 and cover DC to daylight. Well, not quite. Typical coverage is starting as low at about 150 KHz on some units up to about 6GHz on some other units. Nothing I know of covers that entire range but they all include the 160 MHz range where railroads are. They would also cover the 400MHz and 900MHz bands that railroads use for data communications. As a matter of fact they receive AM broadcast, International shortwave, ham radio, TV frequencies (but you can’t decode it on your computer due to bandwidth limitations), FM broadcast, aircraft frequencies, weather satellites, NOAA weather, police, fire, Amateur radio satellites, etc…

Photo 1 is a typical SDR in the form of a dongle. Some units are bigger than a shoebox and includes a transmitter.
Photo2 is a screen display of SDR-sharp, just one of the programs available free for controlling an SDRs.

Hope this is helpful. Sorry I don't have better news. Maybe next year. Just don't kill the messenger.

John



Edited 1 time(s). Last edit at 05/19/14 21:47 by wa4umr.

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Can a mobile antenna (roof mount) be connected to the dongle???

RFandPFan Wrote:
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> Can a mobile antenna (roof mount) be connected to
> the dongle???


Yes. The antenna connector is usually a standard SMA type coaxial cable connector. You can connect a rubber duck type connector to it or you can connect a cable to an antenna on your roof or on your car or anything else you might want to use. The most common cables have the UHF or PL-259 type connector or maybe a BNC type connector. To use those cables you would need an adapter to interface the SMA to PL-259. Other than that, should be no problem. The only warning I give you is that the software is free and other than online documents, there is little support for it. I haven't tried the NXDN decoder add on. I just found out about it last week.

John

What software do you use to decode the NXDN? I use SDR# or gqrx for receive, but those programs can't demodulate NXDN natively. I know it's possible to pipe the audio to a second program for decode, but I don't know what's available for the NXDN decode.

Top_bullfrog
Sacramento, CA

Top_bullfrog Wrote:
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> What software do you use to decode the NXDN? I
> use SDR# or gqrx for receive, but those programs
> can't demodulate NXDN natively.
>
> Top_bullfrog
> Sacramento, CA

There is a program called DSD.exe. You will also need CYGWIN1.ddl. It's a free download. Go to your tube (you can figure that one out) and search for NXDN. There are a few files that look helpful but a few are in something other than American. One called "Complete guide to digital decoder" has some info. It shows a DMR example because there is no NXDN in his area but he says it will decode NXDN.

I'm not sure if anyone is using NXDN around me at this time. I've scanned all channels and haven't heard anything that sounds like digital signals. I have not tried the program myself. I just mentioned it as information for anyone that might be interested. If you try it and have any luck, please let me know. I'll probably listen around and see if I can find anything and then try DSD to see if I can decode it.

Lots of luck,

John, WA4UMR
Edit to correct type



Edited 1 time(s). Last edit at 01/24/15 11:19 by wa4umr.

There's been a lot of discussion on Radio Reference about Whistler taking over the GRE line of scanners. They have brought out some of GRE's scanners with the Whistler name on them but nothing new. Given the time to design and develop, as well as get FCC approval for a new radio I'm hoping Whistler will have something for the Consumer Electronics show in Las Vegas or for Dayton next May... One can only hope!

wa4umr Wrote:
-------------------------------------------------------
> Top_bullfrog Wrote:
> --------------------------------------------------
> -----
> > What software do you use to decode the NXDN? I
> > use SDR# or gqrx for receive, but those
> programs
> > can't demodulate NXDN natively.
> >
> > Top_bullfrog
> > Sacramento, CA
>
> There is a program called DSD.exe. You will also
> need CYGWIN1.ddl. It's a free download.

I'm using Linux, so Windows programs won't cut it and Cygwin isn't needed. I did find dsd in the package manager for my distro(Arch Linux), and after a bit of work with dependencies, I got it installed. Now I have to work out how to get audio passed between the programs(it's never easy, is it? ;-) )

Thanks for the info about the program and the extra resources. I'll check the videos out to find out more about decoding NXDN, and I'll hopefully be able to find a signal locally to practice on.

Top_bullfrog
KI6BZP
Sacramento, CA

A less expensive alternative.

https://www.adafruit.com/products/1497____


I've no knowledge if NXDN software is available.

Be sure to get a "M" to SMA dongle per the ad if
you want to use an antenna other than the one supplied.

Be Well,

Tim Colbert K3HX

I purchased a Kenwood NX700 a few months back...it's been the best radio I've ever owned.

CG Tower



Edited 1 time(s). Last edit at 05/25/14 04:53 by CGTower.

I am planning on purchasing one mobile and one handheld.

The mobile for my truck or as a base unit. Cannot decide yet.

Some of the channels I might program some simple ham channel to play around with the unit.

Pat

WA5VRO
Austin, TX