Interconnect Specialists

Homing in

Joe Moelt, P.E., K0OV PC Box 2508 Fuflerton CA 92633

Hunting For PELTS

Transmitter hunting enthusiasts agree that Radio Direction Finding is unsurpassed as an exciting sport. But just like other aspects of ham radio, it also has the potential for public service. Last time,! (old how hams in Utah and elsewhere use their RDFing skills to help agencies such as the Civil Air Patrol find downed aircraft in wilderness areas.

A well-tuned system is now in place for detecting and tracking the signals from Emergency Locator Transmitters {ELTs)- When a plane makes a hard impact, its ELT activates, putting out 100 milliwatts on 121.5 and 243 MHz (see the photo). Emergency Position Indicating Radio Seacons {EPIRBs} are similar units for boaters in distress.

Passing aircraft, mountaintop receivers, and orbiting satellites provide first detection of ELT and EPiRB signals. Then they are tracked by Search and Rescue (SAR) volunteers and professionals using airborne, marine, vehicle-mounted, and hand-carried RDF sets.

The National Park Service reports that there were 2900 SAR incidents in 198B Only a small fraction were for downed aircraft. Most involved lost or injured individuals. Certainly the search tor an overdue backpacker or avalanche victim would be enhanced if he or she were carrying some sort of beacon transmitter.

Misuse of ELTs

A growing number of hikers and campers are carrying ELT type beacons with them when ihey go into the wilderness Skiers and climbers have gotten interested in them, too. They figure that if they get into trouble, they will be able to take advantage of the massive SAR RDF system already in place.

That's bad news, because today's ELT detection and tracking system was never intended to serve the needs of the 0 million people who take to the outdoors each year. The present ELT system is simply not capable of handling the SAR needs of both pilots and hikers. Using an ELT for anything except aircraft and boating emergencies is illegal, and those who do risk a $10,000 fine.

Already, the false alarm problem with aircraft ELTs is acute Inadvertently activated ELTs sometimes cover up the signals from actual crashes. One source estimates that two million dollars is spent every year just to track down and shut off the ELTs turned on Iby bumpy landings and operator error. Increasing ELT usership will only worsen the problem.

One ham thinks he has a better idea. Communications engineer Kenneth Seymour KA7QSM of Beaverton, Oregon, envisions a separate low-cost beacon service for users of the wilderness. He began discussing his ideas with FCC engineers last year. They were enthusiastic because of the growing problem of unauthorized use

Radio Direction Finding of aircraft ELTs. The FCC urged Ken to submit a Request for Rulemaking (RM), which he did.

KA70SMns proposed system was very simple. The technology would be similar to that presently in use for animal tracking and research Only one or two frequencies would be needed. Transmitters would be low powered and pulsed al a low rate to conserve battery life and to allow multiple transmitters to be tracked simultaneously. Range would typically be one mile.

In addition to wilderness use, the proposal suggested the new service could help parents find lost children in shopping malls and enable police to recover stolen property. Ruggedized transmitters could cost less than fifty dollars. Hand-held RDF sets, including receiver and antenna, would sell for about $150 when mass produced. Voice modes were not included in Ken's service, to prevent its use for bugging.

Discussions with FCC engineers pointed to the 70 MHz region as an optimum RDF frequency range, so KA70SM suggested that the new beacons be put on the model radio control (RyC) frequencies there

The FCC promptly assigned number RM-6681 to Ken's proposal. The Academy of Model Aeronautics immediately objected because members did not want their R/C frequencies used. But very few others commented at that time. Last December, the FCC pressed ahead and issued Notice of Proposed Rule Making (tsiPRM) PR Docket 89599 to create the Personal Emergency Locator Transmitter Service (PELTS).

The FCC Wants More

Of course, the FCC had its own idea about what PELTS should be like. Rather than embracing KA70SM's simple system, the FCC wanted two-way voice communications in addition to RDF, saying it was important to reassure victims and assess injuries High power base stations would be put up by state/local governments, rescue groups, and ski lift operators to talk to the portables. Individuals could own portables, but not base stations.

The FCC proposed 10 frequencies. Only one would be for emergency and homing use. The remainder would be for base to-portable and ponabie-to-portable voice communications Oases would be individually licensed, while portables would operate under a blanket base station license.

The requirement for "10 channels, some of them running high power, eliminated the possibility of using the 70 MHz R/C band. The FCC proposed putting PELTS channels at about 220 9 and 221,9 MHz, frequencies that are to be yanked from the Amateur Radio Service by Docket 87-14, That docket had set 220-222 MHz aside for Amplitude Compandored Single Sideband (ACSSB), a new narrowband technology, PELTS would use ACSSB modulation, with the channels spaced only 5 kHz apart.

The period for comments and reply comments on the PELTS NPRM ended in April. Support for the FCC's proposal has been hard to find Many users of the outdoors want no part qf it They prefer to keep using the ELT frequencies despite the FCC's declaration that this "... could render the existing aviation and maritime distress and safety system ineffective."

KA7QSM isn't happy with the FCC's ve rston of (¿is proposal. Ho says it' s too complex and hard to implement. The requirement for 10-channel ACSSB radios will add greatly to user cost, as will the need to establish and support a network of base stations.

United Parcel Service does not like the PELTS proposal, either. According to Ken, UPS wants the entire 220-222 MHz segment for its exclusive use.


The ARRL filed against PELTS, too The primary reason, of course, is that the matter of 220-222 MHz reallocation is not closed, and is moving into the courts True enough, but the ARRL went further, claiming that rules compliance would probably be poor, and that PELTS is impractical because most receivers and scanners presently do not cover the proposed frequencies

Well, that makes about as much sense as someone saying 20 years ago changes, PELTS could become simpler, as Ken hopes, or more complex, perhaps in volvi ng satellvte technology.

The biggest problem facing PELTS, or any other new service idea, is finding a place in the crowded spectrum to put it. Here are my thoughts: Let's get back to basics and make PELTS an emergency beacon system for wilderness RDF and rescue only. People who want voice communications in the boonies have plenty ot other options, including CB, ham radio, 49 MHz. and itinerant VHF business channels. Without voice provisions, the potential for PELTS rules non-compliance is greatly decreased

Eliminating the voice communications aspect of PELTS would make it simple and affordable for every hiker. Only one low power frequency would be needed. It should be selected for optimum RDF characteristics. The PELTS beacon frequency could be shared with a wideband service, such as TV broadcast.

I can hear you say, "Sharing with TV is impossible!1' But, it is being done right now. Large numbers of flea-power wildlife tracking and telemetry transmitters are beeping away as you read

ELTs are designed for mounting in the tail of a plane, tike this one, but increasing numbers of hikers and campers are carrying them. (Photo by WB6UZZ.)

that cellular phones would never be popular because nobody had receivers for them. Just as cellular technology did then, PELTS wit! open a new market, and equipment suppliers will appear quickly. There is no need to restrict PELTS to popular scanner frequencies

I agree that 220 MHz is not the right place for PELTS, but for a different reason. On-foot RDF in hills and mountains becomes much more difficult as frequency increases. Compared to VHF, reflections are tar more pronounced at UHF; just ask anyone who has hunted on 220 or 450 MHz. Multi-path slows down the PDF effort, which is certainly undesirable when lives are at stake. Multipath is severe enough on 121.5 MHz. but it is even worse at 220 MHz.

KA70SM1s proposal would have put PELTS at 70 MHz, which is a good compromise. That frequency range is low enough to avoid severe muitipath from most terrain features Lower frequencies would not be practical, because efficient transmitting antennas would get quite long, and sensitive RDF antennas would become too large for easy on-foot use.

Round Two

What will happen to PELTS? KA70SM thinks that the FCC will re-issue the NPRM with significant this, on frequencies ranging from 27 to 500 MHz. Biomedical telemetry from hospital patients is being transmitted at this moment from 174 to 218 MHz, which comprise TV channels 7 through 13. Many sou nd systems have wireless mikes there, too.

There is no unwanted QRM from these bio-emitters. Transmitter power is so low that no herringbone appears in anyone's picture. Wildlife RDF is successful because there is little television signal energy in the DF set s narrow passband, if the selected frequency is kept away from the TV video, audio, and color subcarriers.

How about a tiny piece of channel 5 (76 to 82 MHz)? Even if by some quirk there were a bit of TVl, it would only be at very short range, and would draw attention to the need for a rescue.

A dedicated rescue beacon system for users of the outdoors is sorely needed Docket 89-599 cited the request of an international SAR council for the FCC to deal quickly with the problem of the public's demand for personal locating beacons. The longer the delay in establishing a service like PELTS, the more people will use aircraft ELTs inappropriately.

Both ELT and PELTS offer opportunities for hams interested in RDF to get involved in public service. "Homing in" will be watching for new developments. Let me know your thoughts.

^^^ Number 27 on your Feedback card

Rtty loop_

Amateur Radio Teletype

Marc i. Leavey, M.D., WA3AJR 6 Jenny Lane Baltimore MO 21208

Remember PiCON?

As this column is being written, in late August, the newspaper, TV, and radio are filled with daily reports of the unfolding crisis in the Middle East. To the averaye citizen, these me-

style machine in the dust. Included with the machine were both DOS and Windows 3.0, Well, kind of.

After unpacking and setting up the machine, a computer magazine arrived with a review article on Windows, which indicated that integral with the new Windows package was a program called Toolbox, which enabled the construction o1 Windows applications.

you'll pardon the expression, a RTTY loop supply. It seems that some of you are building or using a solid state interface which is. itself, looplessl

Well, fret no longer. See the figure for the solution.

This is a straightforward supply, which features a low voltage, current-limited output fully capable of powering an old Model 15 teleprinter, tt keeps the voltage low enough to prevent frying those silicon chips that are overtaking cur shacks.

The parts for this little darling should be easy enough to obtain, either from the electronics emporium in your local mat! (there táoneof those "RS" [Radio Shack] stores near you, isn't there?), or from any of a number of mail order firms, If you really want to build something, this or any project and still can't find a source, let me know, and we ll devote some space to it.

Meanwhile, I look forward to your comments, suggestions, questions, contributions, and critiques. Send them to me at the above address, or by way of Email on CompuServe (ppn 75036,2501) or Delphi (username MARCWA3AJR), Believe me, I look forward to reading every one of them! iffl


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