Category Archives: Radio Stuff

Sharing Scanner Audio on the Internet

For a couple of years now the Gopher Amateur Radio club has been provding scanner feeds of the digital APCO-P25 in the Minneapolis/St. Paul metro area to radio enthusiasts around the world through the website (now a part of the family). In fact, I specifically purchased the fabulous GRE PSR-600 to replace the Radio Shack PRO-2096 because it allowed us to transmit the talkgroup identifier as well as the audio though some hacks attaching the remote control software to the stream broadcast software.

Thanks to K1PGV it looks like there is now some software called ScannerCast which integrates the polling function to get the talkgroup ID for both Uniden and GRE scanners which support it and tag the audio with the talkgroup. This is a much neater solution, if a little bit more limiting in that it doesn’t allow for simultaneous remote control of the radio.

Packet Radio With Soundcards Including APRS

This summer I decided to explore a bit more about packet radio. You know, transmitting small amounts of information over amateur radio frequencies at very slow speeds. Prior to the advent of fairly ubiquitous high speed Internet connections this was a popular way for hams to move around information related to their activities. As it turns out the need for a dedicated packet modem (TNC) has gone away and the functionality can now be replaced with software and a sound card. One of my specific interests though was in learning about and improving the APRS system in the Twin Cities which allows people to automatically send GPS position information along with remote weather station packets and a variety of other small pieces of data. As it turns out APRS data can also be sent and received with a soundcard attached to a radio, forgoing the TNC and reducing the barrier to entry.

The primary program for soundcard TNC emulation is a free program called AGWPE and my first task was to learn how to setup and configure it as some of my firends had tried and failed to get it working in the past. Thanks to the great resources on the Internet I came upon the website of KC2RLM which contained excellent instructions for setting up and using the AGWPE program as well as a number of applications which would interact with the software.

Once I had gotten the basic soundcard TNC software up and running the next step was to start experimenting with APRS software. I tried lots of software including the common UI-View32 software but found the easiest to use and most modern software to be AGWTracker, a trialware program by the maker of AGWPE which supports all kinds of map layers such as Google Maps, MapPoint, etc. greatly improving the user experience. Of course, if you want to send updates back to the APRS-IS Internet network you need a password to go along with your callsign. As it turns out the password is a simple hashing algorithm designed just to prevent non-hams for injecting data into the network and is a documented algorithm. You can get your own APRS password or learn more about the algorithm at the APRS Password Generator website.

D-STAR Projects

One of the many misconceptions about the D-STAR digital amateur radio protocol is that it is closed and will prevent tinkering by hobbyists. This turns out to be far from the truth indeed. Last year at the Dayton Hamvention there were several exhibits by D-STAR enthusiasts which included an entirely home brewed D-STAR radio and a home brewed D-STAR repeater controller. Well now someone has built a DV interface adapter which can provide a D-STAR digital voice interface on many existing transceivers. Of course some functionality is missing as there is no ability to change various DV settings from the minimal interface but it proves yet again that there is the possibility for much experimentation with this new digital mode.

On other fronts the OpenDSTAR group has released several software tools which build on existing commercially available repeaters and Internet gateways to extend functionality. Still in the pipe from that group is a USB dongle called the DV Dongle which will allow end users to encode audio in the AMBE format used by D-STAR digital voice for later playback through the repeater or, ostensibly, for live PC to repeater communications. Indeed the home brew spirit of amateur radio is alive and well in the world of digital communications, it just looks different than it has in the past.

Online Amateur Radio Repeater Directory

I recently found the website which contains a listing of many of the amateur radio repeaters in the United States. I actually had a plan at one point to develop a similar PHP/MySQL driven site but simply have way too many other projects going to take on another. That said I do have a few issues with the US Repaters site. First, the site is a mess graphically and navigation leaves a lot ot be desired. The lack of an interface for owners of repaters and/or coordination bodies to make changes, users to search, etc. is also unfortuante. Secondly, the data is copyright instead of being open and freely available. As inexpensive as webhosting is these days and seeing that ham radio has a long tradition of sharing knowledge I am disappointed to see someone attempting to assert control over this factual data. I think a simple ad supported site (not the ads all over approach US Repeaters takes) would be sufficient to support such a directory. If someone out there is interested in working on an open PHP/MySQL repeater directory I would be more than happy to provide web space, bandwidth and my ideas. Contact me if interested.

Decoding MDC Data

Many towns, counties and states still using analog based radio communications systems for public safety use Motorola MDC systems which emit a short “chirp” at the beginning or end of a radio transmission. If this is the case in your area you might be interested in the open source WinMDCD software. This software allows you to decode that chirp with a Windows based PC and see data such as date, time, unit ID or whatever else they’re transmitting. Note that if you’re interested in Motorola radio technology a great resource is BatLabs, in particular the BatBoard which has a great number of people who are extremely knowledgeable about Motorola radios.

Radio over VoIP

In a followup to an earlier article about the Cisco IPICS system I have received some additional information that seems to indicate my preliminary analysis was correct. If you remember when Cisco launched their IPICS ’emergency communications system’ I suggested it was really more of a way to tie existing communications systems together than a new system itself.

It seems that Cisco has been looking into this for a while and ostensibly created this product to fill an internal company need for connecting disparate communications systems. This case study explains how Cisco created a Land Mobile Radio (LMR) over IP product to fill a need to communicate with their own security personnel. The end product is described in this Cisco whitepaper entitled “Cisco Land Mobile Radio over IP Solution Reference Network Design”.

The LMR over IP product is a card which can be installed in any of the voice capable Cisco routers and provides an interface that connects full-duplex VoIP datastreams to speaker, mic, push-to-talk (PTT) half-duplex devices. Signaling is via standard H.323 and the card uses RTP audio with a variety of codecs. The card used is called a VIC Ear and Mic (E&M) interface and was originally used to connect VoIP to some legacy PBX hardware. Technical information about the E&M interface can be found in this technical publication. If your LMR equipment supports a half-duplex T1 that can be used as a trunk interface instead.

As a friend pointed out the existence of support for this type of configuration presents some interesting ideas for amateur radio VoIP projects. Without going into too much detail the current preferred methods of connecting amateur radio stations with VoIP is to use either the Echolink or IRLP project. Both of these have a significant number of problems, one of which is that they require a computer to be attached to the radio. It would be much nicer to attach a (more stable) router to the radio instead. This merits some more research. Once you got a radio attached to a VoIP phone system such as Asterisk there’s all kinds of interesting possibilities.

A Real Scanner

While it’s prohibtively expensive to build the Equinox radio scanner probably represents the pinnacle of radio scanning equipment today. A fully remote controllable PC based radio (RF) scanner this is truly the Cadillac monitor.

From its home in the Seattle, Washington area, the Equinox receiver provides continuous, remotely-accessible coverage of the DC-1 GHz spectrum on a 24-hour basis.

While it would be a bit much for individual hobbiests to build one of these it would be cool to see scanning clubs such as Minnesota based ScanFan get together and buid one for community use. The internet provides a great way of participating in this increasingly expensive hobby (as more systems go digital) if we could allow for some remote control and data from the reciever(s).

Cisco announces emergency communications integration system

This week both ComputerWorld and NetworkWorld carried the story about Cisco announcing their IPICS product. Unfortunatly, the headlines, if not the articles, are misleading or at least confusing in their description of the product.

Ever since September 11 there has been a big discussion in the emergency services community about the need for communications interoperability. Out of this discussion the APCO Project 25 standard for public safety digital voice systems emerged. The big downside is that this requires the (expensive) replacement of radio equipment in the service area. While many states have started statewide P25 programs (such as the ARMER project in Minnesota) full capabilities are still a long way off.

With the recent natural disasters there has been an increased awareness of the challenges faced by communications interoperability. My understanding of the Cisco product is that it is a server and gateway product designed not to create a new communications system (a la Project 25) but to tie existing Nextel talkgroups, cell phones, VoIP systems and radio systems together for emergency communications. Think of it like an autopatch on steroids. It’s certainly a big undertaking, especially when you consider how reliable and easy to use it needs to be in emergency situations. It’s pretty tough to explain the server going down and cutting off communications in these situations. It will be interesting to see how Cisco fares in the public safety market which is decidedly different from areas they’ve been in before. For more information on the IPICS system check out the Cisco product annoucement and get it straight from the horse’s mouth.

Scanning Minnesota

First there were the analog systems, then the trunked analog systems, then the metrowide digital system and now the statewide digital system. This is one hack of an administrative nightmare, it’s a good thing we’ve got tons of committees working on this. In any event the following are some useful links for exploring Minnesota’s digital system(s).

Scanfan is always a good palce to start when you’re talking about metro area Minnesota scanning. Unfortunatly their server got hosed early this year and they lost a lot of good stuff, it’s slowly coming back though. They have a lot of the metro municipality/county analog frequencies listed on their site.

One of the members of Scanfan created this nifty database of talkgroups and frequencies for the metro digital system, they’ve also added some analog frequencies. The whole database is searchable and downloadable and it’s a pretty nice project.

If you’re looking for detailed technical information, policies and diagrams of the metro digital system the place to start is at the Metropolitan Radio Board website. They have nice transmitter location diagrams, system explanation and all the other juicy technical details of this engineering marvel.

The newer statewide board, “Allied Radio Matrix for Emergency Response” (ARMER), is picking up where the metro board left off and taking the system statewide. They too have a webpage with some useful information, though not as thorough as the metro board.

Some additional information on the workings of the digital system and more talkgroup IDs can be found at the MN_Metroscan website. Another local scanner/ham enthusiast with a good webpage of digital talkgroups and analog frequencies in the metro area is ECMscanning. also has a page with some information on the ARMER system.

As for myself, after some debate over GRE (RadioShack) vs. Uniden and mobile vs. handheld I went ahead and purchased the Pro-2096 and the “purple” PC programming cable and plan to purchase the Win96 programming software which is widely regarded as the best.