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

http://en.wikipedia.org/wiki/Ricochet_(internet_service)

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.


http://www.tapr.org/fhss_project.html

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: http://www.tapr.org/tapr/html/taprfhss.html

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: http://www.dandin.com/tdr900.html

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.

Experimental 900 MHz Ham Radio Repeater

What I like about 900 MHz is that there are no off the self radios that you can buy. That may sound crazy.  But I wanted a project where I could get back to the basics of the hobby and learn a few things in the progress.

I created a 900 MHz overview on my the projects part of my webpage.  I hope this can prove to be a great overview of getting going on this band. I have received many compliments from others already.

Below is the start of documentation to a 900 MHz repeater that I have been working on.

It uses a 800 MHz Motorola Maxtrac as a receiver that has been converted to 900 MHz. See the Repeater Builders page on this: Converting an 800 MHz MaxTrac to a 902 MHz Repeater Receiver.  These are cheap and have great receive sensitivity. There are people on the AR902 list that sell them, with the conversion to conventional firmware already done. In some cases they have the filters pre changed or jumped too. These converted receivers can usually be found for about $60. On mine I replaced the filters with 915 MHz centered Murata filters rather than shorting as this provides further rejection from out of band pagers and what not.

A receive signal COR or CAS logic had to be exported so that you can interface the radio to a controller or have some signaling to be able to make the other radio go into transmit on reception of a signal. I like the Motorola M120, Maxtrac, GTX and GM300 line of radios as picking off a COR and exporting receive audio are all fairly simple and these mods can be work universally so you can mix and match these types of radios. You don't need the expanded 16 pin logic models. All the exports can be done using un-used microphone pins.

The transmitter is a 15 watt Maxtrac. These are good fairly rugged transmitters when compared to the other options such as the GTX.

I extended the MaxTrac 900 MHz VCO Frequency Range using a conductive ink pen. Obviously these radios were not intended to operate on the ham freq's. Even the radio's that are capable of this ham band that do not necessitate hardware mods, the programming software doesn't recognize amateur frequencies. At the very least you have to hex edit the software. Even after you trick it into letting you enter those frequencies, many of the radios' have VCO locking problems and won't transmit (or receive) in various sections of the ham band with out some of these hardware mods.

I also realized that I may later need a fairly dynamic control of the output power to meet various (low) drive requirements for an amplifier. The Radio Service Software allows for small power adjustments, but generally those software controls are considered unstable beyond a 3 dB adjustment.  So manual power control mods were necessary.

The duplexers are TX/RX. Contrary to what most assume, you can tune a duplexer with nothing more than a HT as signal source and watt meter. You don't really need a fancy service monitor. It's always desirable for greater accuracy, but not necessary.

There is some good info here: http://www.seits.org/duplexer/duplexer.htm

When I need very week signal to test a receiver or antenna a police scanner can do the trick. If you can find the IF (intermediate frequency) of the scanner, you can add that (10.85 MHz in my case) to the intended freq that you need a signal on. You should have a very week "birdie" where you need it.

I'm using a very simple repeater controller. It's the Ham Gadgets ID-O-Matic Kit. It's very small and only $20. I am also still experimenting on simplex with devising my own more multi functioned Linux based controller.

I also am using a Janel Model PF849D 900 MHz 10 dB 26 volt preamp that I picked up at Grayslake for $10.

This system is On the Air on 927.5125/902.5125 with a Digital PL of 223. It's presently into a crummy Maxrad MN9155 5 dB 900 antenna that I have at 45 feet on my tower feed with LMR-400. I have to say I am rather impressed. This is pretty cool considering the antenna gain probably makes up for the coax loss at best.

For anyone who might be from Wisconsin, I want to let you know that at the WAR meeting back at the end of April, the ARCC bandplan was adopted for 900 MHz use in Wisconsin. It's works much like the SERA bandplan, which is the well known one that accommodates both 12 MHz & 25 MHz repeater splits. The advantage of the ARCC plan is that it doesn't interfere with any existing areas for other modes like SSB/week signal, etc.

HSMM with the 900 MHz Aerocomm modem

High Speed Multi Media (HSMM) is often referred to as being the Hinternet (Ham Internet), as it is primarily used under FCC Rules & Regulations Part 97. Under Part 97 commercial off-the-shelf equipment can be used at higher power and higher gain than the more common Part 15 802.11a/b/g operations.

The primary purpose for HSMM and Hinternet is to augment emergency communications via long range high speed wireless data networks that can handle voice, data and video communications. HSMM can also be used in the day-to-day aspects of Amateur Radio Communications.

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The AeroComm CL4490, is a 1 watt 900 MHz, frequency hopping spread spectrum (FHSS) serial modem that can yield 20-25 kbps of throughput. They are about $100, which is really quite reasonable considering the price of a conventional TNC and radio.

The actual RF module itself (AC4490) can be bought for $62. The complete AeroComm CL4490 transceiver includes the AC4490 module housed in a nice aluminum case with an internal switching power supply and the necessary RS-232 to TTL conversion circuit.

We have experienced solid mobile non line of site coverage for 3 miles, with mobile coverage extending to 6 miles depending on terrain. This is with a measly 6 dB base station at 35 feet. Distances over 20 miles line of site are theoretically possible with these.

For more information on the Aerocomm, and to obtain specifics on the network configuration see:
http://www.qsl.net/n9zia/aerocomm/

HSMM Information Resources:
http://en.wikipedia.org/wiki/Hinternet
http://www.qsl.net/kb9mwr/projects/wireless/plan.html