Sunday, August 30, 2009

APCO 25 decoder /analyzer

Matt Robert, VK2TVK writes in the APCO25 ham radio list:

Hi List,

I would like to let you guys know about an open source P25 decoder/analyzer project that has been running for a little while now. OP25 started as the thesis for a Computer Security PHD student that is researching the security aspects of the APCO25 standard. The software is being expanded into a decoding suite that can gives various bits of information about a received signal and there is also provision for a software based repeater.

OP25 is based on the open source GNUradio package, and it is compatible with either the USRP software radio peripheral, or a conventional NFM radio connected to a sound card via a discriminator tap. One contributor is also working on adding transmit code with the intention of giving a software based P25 repeater that can be run off conventional PC hardware. Currently all the major contributors are HAM operators.

At the moment OP25 is considered pre-alpha (i.e. developmental) and we are looking for people that are interested in becoming developers/contributors to the project. The project is designed to run under GNU/Linux and it requires a bit of skill to get it going. It's definitely a HAM radio project at this stage and that's why I figured it would be appropriate for this list.

Shown here are are some sample screenshots for the curious.

Please feel free to have a look at the project homepage at and there is also a discussion list at

Kind Regards,

[Update Dec 2009]
Here is an interesting amateur video, that demonstrates the OP25 code in action with GNU radio using the USRP.

[Update April 2012]
Here is an updated video, showing OP25 code with GNU radio using a cheap USB TV tuner as a replacement to the USRP.

Saturday, August 22, 2009

Re-Crystaling WRT's

Some hams in Germany have been recrystaling Linksys WRTs to go outside of the Part 15 band: Arsene, LX1TB has modified the Linksys WRT54G(S) models to tune the frequencies below 2400 MHz for better fit with the hamradio bandplan.. Look on these German websites to get the details:

Translated version of :

And translated version of:

At the recent Ham-Com convention in Texas, Kipton, Moravec, AE5IB and Glenn Currie, KD5MFW made this chart with the data about the crystal change.

The whole screen is the amateur radio spectrum allocation in that frequency area.

The top section is the standard off the shelf WiFi. You can see that Channels 1-6 fit into the spectrum.

The second section is replacing the 20 MHz crystal on the transmitter with a 19.6608 MHz crystal (the next lowest that is readily available and costs under $1) With it we can use channels 7-11 in our band. Other countries allow the unit to have Part 15 channels 12-14.

The third section is the ARRL Band plan. he notes, because we are spread spectrum, we look like background noise to the narrow band signals.

Kipton tends to think maybe with a software change we can add those channels also and with the crystal change still be in the Amateur Radio Spectrum.

With the crystal changes, the units can not be detected by unmodified standard 802.11 devices, and impossible for them to connect.

The tests showed that by making a simple 59-cent crystal change the HSMM signals could be moved to between IEEE Channels 2-3.

Also show at the Ham-Com HSMM presentation is a spectrum analysis from Wi-SPY by MetaGeek.

The yellow shaded area shows the official 802.11 Channel 2 center. The red shaded section shows the official 803.11 Channel 11.

The CPU clock and ethemet clocks are totally different from the radio crystal, so both units "think" they are on Channel 11. Only the crystal-modified "slide band" unit is somewhere between Channels 2 and 3 as shown by the green and blue accumulated readings. Both units were tested for about 3 hours for frequency stability, etc.

You can read more about this in the latest (Summer 2009) CQ-VHF Magazine HSMM column by John, K8OCL Titled "New Amateur Digital Video (ADV) and Revolutionary HSMM-MESH at Ham-Com."

Monday, August 17, 2009

Spread Spectrum and Ham Radio

All though the 80's and 90's the big thing one kept reading about was spread spectrum and how it would revolutionize ham radio.

So lets take a trip down memory lane:

TAPR's Statement on Spread Spectrum Technology Development

TAPR was founded in 1982 as a membership supported non-profit amateur radio research and development organization with specific interests in the areas of packet and digital communications. In the tradition of TAPR, the Board of Directors at their Fall 1995 meeting voted that the organization would begin to actively pursue the research and development of amateur radio spread spectrum digital communications. At the Spring 1996 board of directors meeting, the following statement of purpose was passed:

"TAPR believes that the technical facts support our conviction that conventional and spread spectrum systems can coexist without detriment to conventional systems on all frequencies from MF to EHF. To this end, TAPR will begin to research spread spectrum systems that will develop technology for future deployment."

As stated above, the TAPR board feels strongly about TAPR's focus on spread spectrum technology and especially how it relates to the potential coexistence on frequencies that will have increased number of users occupying them. The amateur radio bands, like other spectrum will become more heavily utilized in the future. It is in the interest of amateur radio to develop systems that are interference-resistant while not interfering with other primary or secondary users on those frequencies.

TAPR understands the concerns many have with the new technology, and believes that efforts in both education and research is necessary in order to allay the fears about interference and to demonstrate the benefits of the technology.

TAPR believes that todays' communications technology is moving toward all digital transmitters and receivers. These advances in technology, combined with the swift evolution of cell based transmission and switching protocols, are opening up a new set of possibilities for unique new services utilizing intelligent networks. These will contain smart transmitters, receivers, and switches. Today's Internet is perhaps the best example of a self-regulating structure that embodies these new technological approaches to communications in the networking domain. However, to date, many of these innovations have not moved into the wireless networking arena. TAPR will work on moving these innovations into the amateur radio community.

TAPR feels that the VHF/UHF/SHF radio networks of the future will involve a mixture of links and switches of different ownership, which terminate at the end-user via relatively short-distance links. What will then be required is a built-in, distributed, self-governing set of protocols to cause the network's behavior to make more efficient use of a limited, common shared resource, the radio spectrum. Creating such a self-regulating structure for the optimal sharing of spectrum will require much effort.

One of the major problems which stands in the way of these new approaches today is the current FCC regulatory environment and the manner in which spectrum is managed and allocated under its rules.

Historically, the current regulatory approach to radio has been based upon the technology that was in use at the time that the Communications Act of 1934 was framed, basically what we would call today, 'dumb' transmitters speaking to 'dumb' receivers. The technology of that time required reserved bandwidths to be set aside for each licensed service so that spectrum would be available when needed. Given this regulatory approach, many new applications cannot be accommodated since there is no available unallocated spectrum to 'park' new services. However, given the new set of tools available to the entrepreneur with the advent of digital technology, what once were 'dumb' transmitters and receivers can now be smart devices which are capable of exercising greater judgment in the effective use and sharing of spectrum. The more flexible the tools that we incorporate in these devices, the greater the number of uses that can be accommodated in a fixed, shared spectrum.

Therefore, TAPR will focus its spread spectrum effort in the following areas:

* TAPR will work to promote rules and technologies to make the most efficient use of the spectrum through power control, forward error correction, and other means to minimize interference among spread spectrum users and existing communications systems.
* TAPR will work on issues and efforts with other national organizations to change the regulatory environment and rules in order to promote the experimentation, development, and later deployment of spread spectrum technology.
* TAPR will work to develop information on the topic to help educate members and the amateur community as a whole about spread spectrum technology, and to disseminate this information via printed publications, the World Wide Web, presentations at conferences and meetings, and other means.
* TAPR will work to foster experimentation, development, and design of spread spectrum systems, and to facilitate the exchange of information between the researchers and other interested parties.
* TAPR will work to develop a national intra-network to foster the deployment of future high-speed spread spectrum systems into regional and local communities, including the development of suitable protocols and guidelines for deployment of these systems.
* TAPR will work with commercial companies who manufacture spread spectrum devices which operate in spectrum shared by the amateur radio service (ARS), in order to make them more aware of the nature of ARS operations on those bands with the goal to work towards the deployment of devices which will minimize interference between all spectrum sharing partners.
* TAPR will work with commercial companies who manufacture spread spectrum devices in order to identify equipments that can be either used or modified for use for Part 97 operation.

Adopted by the TAPR Board on September 20th, 1996 at SeaTac, Washington Board Meeting.

Spread Spectrum Statement Committee:
Greg Jones, WD5IVD
Dewayne Hendricks, WA8DZP
Barry McLarnon, VE3JF
Steve Bible, N7HPR

In 1994 Merticom, established them selves as owner of Ricochet Networks was one of the pioneering wireless Internet service providers in the United States. They provided 128 kbps broadband services to the general public using unlicensed 1 watt 900 MHz FHSS radios mounted to light poles in several major cities by 2001, just before the filed for chapter 11 bankruptcy. At the time, many hams in these large cities complained that the Ricochet Networks made the 900 MHz band virtually unusable due to the high noise floors caused by the wide deployment.

The TAPR FHSS Radio project was displayed at the 1997 ARRL and TAPR Digital Communications Conference, October 10-12, 1997 and officially started that year.

The development of this 1 watt, 128 Kbps 900 MHz FHSS radio, suggested this is the future for amateur packet radio.

October 1999 TAPR signed an agreement with the Dandin Group to take the TAPR design from its current state into production which TAPR has access to production for sale back into the amateur radio community. This is an agreement we have been working on for several months. The bringing together of TAPR's and Dandin's capabilities will help the speed of the project tremendously.

Dewayne Hendricks (WA8DZP) , was the CEO of Dandin Group. Dewayne stated that Dandin was trying to do something like what Metricom was doing, but we were trying to do it in a different way than they were doing it, a different business model.

"The first release of the TDR-900 is designed to operate at 900 MHz with future radio modules to cover other parts of the spectrum."

From October 1999:
TAPR has signed an agreement with the Dandin Group to take the TAPR design from its current state into production which TAPR has access to production for sale back into the amateur radio community.

From Dec 2001:
The TDR-900 is being developed for both commercial and amateur radio deployment. Dandin will be handling the commercial interests in the radio, with TAPR handling the amateur radio service.

The system has been designed so that the digital and RF board are separate units. Additional bands for the radio are in development.

More information on technology availability and licensing will be available once the technology transfer between TAPR and Dandin is complete.

In the fall of 2002 TAPR announced it would discontinue it's stalled 900 MHz FHSS radio efforts. The project did not reach completion as they were faced with continuing parts obsolescence problems that resulted in continual redesign, and second, we were unable to obtain the RF design expertise needed to finalize the RF board.

The TAPR Spread Spectrum Radio

Tucson Amateur Packet Radio (TAPR) has announced that a team led by Bob Stricklin, N5BRG, Bill Reed, WD0ETZ, and Tom McDermott, N5EG, is developing the TAPR Frequency Hopping Spread Spectrum radio. At last report, the prototype radio was transmitting, although not yet hopping. The group spent about $15,000 on the project last year-on things like pc board prototypes, development software, parts, and other odds and ends that a project of this magnitude requires and anticipate spending another $15,000 to $30,000 on it in 1999. Thus far, though, TAPR has received a little less than $2,000 toward its overall goal.

TAPR will be sending out a fund raising letter in the next few months to help fund all or part of the costs of this development project. Members are being asked to donate to this worthy cause, and I'm asking the readership of CQ VHF to also consider supporting this valuable project. Please take a serious moment to consider this request and help bring this unique project closer to completion. If you have contact with a local or regional packet organization, contact them about supporting this project as well.

Donations above $25 will receive a handsome certificate acknowledging their contribution to the TAPR FHSS Project, while those donating $250 or more will receive a plaque to let everyone know of their efforts on behalf of this project. All donations are needed and welcome, no matter how large or small. Even if you simply become a member of TAPR-well worth the $20--you can be sure it's appreciated and helpful. Thank you for your consideration. Contact TAPR at 8987-309 E Tanque Verde Rd #337, Tucson AZ 85749-9399; (Phone: (940) 383-0000; Fax: (940) 566-2544. Internet: . Visa and Mastercard are accepted.

-Per N2IRZ, CQ-VHF Magazine, March 1999

The funny thing is you really don't read much about spread spectrum & ham radio anymore. It appears that the main guys who were beating the ham radio drum initially on this apparently made a buck off it in the commercial market.

Which is a dirty shame. I was a follower of the project having been involved in conventional packet radio and seeing the need for speed. Of course the idea of modifying Part 15 spread spectrum radios was never really promoted by TAPR because that was a direct conflict of what was trying to be marketed.

This TAPR / Dandin FHSS radio project wasn't fully successful for them as the project never made it to completion. The reminds me of how ham radio was a test bed, or example for how AMBE / D-Star works. This has given Icom and Kenwood a chance to perfect it and unveil it for APCO25, Phase II.

Lesson learned; commercial influences like this can sometimes screw-up a potential good thing for this hobby, and other times (like with D-Star) being the Guinea pig can help breed some new developments into the hobby and work out for the commercial entity.

Sunday, August 2, 2009

The Amateur Radio Emergency Communications Enhancement Act of 2009

This was a ARRL news piece a while back.

The ARRL is asking its membership to contact their members of the US House of Representatives with a request to become co-sponsors of this significant piece of legislation.

While this is all nice in theory... Where does one click or write to, to encourage new technologies that can help aid and advance how we communicate in emergencies? Surely if the ARRL can adopt Winlink 2000 for ARES emergency communications, they could also get behind some development of something more modern?

We had something more logical, a wide network of packet backbones in the 80's and 90's. Yet some how we end up with this bastardization called Winlink.

In the April Rain Report, CQ Editor Rich Moseson, W2VU, talked about packet's remarkable comeback and its EMCOMM applications.

About ten years ago a survey conducted by the ARRL Technology Task Force, of League members and other amateurs revealed that the number one interest in new technologies was in high-speed digital networks.

This is what led to the development of the High Speed Multi-Media working group in 2001-2005, appointed by former ARRL President, Jim Haynie, W5JBP.

The HSMM working group was an loose attempt to steer ham radio into the future by bringing awareness to the general ham populous of what is possible with HSMM.

It really could evolve into something powerful, the "next generation of ham radio." But it needs a leading force for that. The ARRL and TAPR both seem to have no interest. In my opinion, they should both be working on the community/ public relations with companies like Ubiquiti, and developers like the DD-WRT guys. Encouragement to work together and enabling hams would not only be beneficial for the hobby, but also the general populous. The HSMM working group encouraged hams, but neither larger group did anything to enable further experimentation.

I have pointed out that 802.11 and WiMax manufactures like Ubiquiti have the potential to develop built-to-order products for HSMM on VHF/UHF bands.

The Ubiquiti XR-1 is the first VHF 802.11 radio that I know of.

It's just a dirty shame someone like the ARRL or TAPR can't establish a better working relation with companies like this. Something like the XR-1 would be an inexpensive powerful Emcomm tool.

I encourage you to write to your section manager if you realize that legislation alone can't advance how we communicate.

Additionally TAPR is seeking nominations for a few good people to serve. So if you, or know of a ham with some fresh ideas, speak up!