Compustar Amateur Radio

Interference Device

Available at a Car Alarm dealer near you!

Operational Frequency: 447.700 MHz

See Compustar Responds to requests from amateurs to use a different frequency! updated July 5, 2000

< Interference pdf file which is a memo style report suitable for publishing. (June 13)
< What the repeater sounds like with Compustar

Below is an explanation of this interference issue. The links are handy for those that wish to pursue further research.

Be advised that there is a car security alarm (www.compustar2w.com - Firstech, Inc. an Alaska company) being sold that operates on 447.7000 MHz as the link between key fob and car.  It boasts a range of a 1/4 mile and can also be used as a remote car starter.   

Their use of the ham frequency is legal under Industry Canada RSS-210 and FCC part 15 due to it's low power output.  Unfortunately, while the signal strength qualifies under the specification as unlicensed, it is strong enough to be heard through a repeater from random cars in the vicinity of a few kilometers.  Most time of the day or night, the data bursts from one car or another can be heard.    

The Compustar device is supposed to be momentary, active only when there are changes in status or an alarm condition.  However, perhaps due to the Korean-English instruction manual, or inexperienced installers, a few  Toronto area firms have been installing the alarm device miswired to the brake circuit, so that they transmit continuously while the vehicle brakes are depressed...  for a repeater in a large city, there are always many cars to be heard.   In Toronto, due to dysfunctional traffic patterns, brake pedal application exceeds throttle application.  The Compustar effects are audibly worst during "rush hour" when most traffic isn't moving.   

The interpretation of the alarm's "momentary" nature is one issue and the way it can be erroneously installed.  While hams can cry fowl about the use of 447.7000, (it really is unfortunate) this isn't an issue according to current regulations.   Firstech/Compustar could have legally picked a public safety frequency too. Rather, it is how the alarm device shares the frequency (or lack thereof).  Once there are enough of these alarms in existence, the frequency becomes unusable for incumbent repeater input applications.  

FCC documents stipulate: 

15.231(a3) Periodic transmissions at regular predetermined intervals are not permitted. However,

polling or supervision transmissions to determine system integrity of transmitters used in security or

safety applications are allowed if the periodic rate of transmission does not exceed one transmission of

not more than one second duration per hour for each transmitter.

and,

15.231(a4) Intentional radiators which are employed for radio control purposes during emergencies

involving fire, security, and safety of life, when activated to signal an alarm, may operate during the

pendency of the alarm condition.

FCC web pages provide the test report on this device (as well as pictures, schematics, certificate), and list it as compliant.   

Industry Canada's Toronto District Office was notified about this interference.  IC has confirmed the emissions and note that the Compustar device has not been submitted to IC for approval under RSS-210.  It's operation in Canada is, at the time of this memorandum, illegal.  Further importation has been voluntarily ceased by the distributor until the device gains IC approval.  However, this is usually a formality.  Submission of the FCC lab report often provides all the necessary information for a rubber stamp approval in Canada.  The Ottawa certification lab has been made aware of the "momentary" issue and will examine it further.  Once the instruction manual is clarified, and steps are taken by the Compustar distributors to ensure miswiring doesn't occur, this alarm will be granted Canadian approval and will continue to proliferate.   

Unfortunately, the damage has been done.  Many miswired alarm units are already in the hands of consumers.  They will not be removed from service unless they fail.

It follows that with many of these car alarms now on the road, the repeater VA3BMC 442.700+ PL 103.5 Hz has been rendered unusable.  The repeater has always been PL access which has hidden the problem until it was unbearable. The Compustar data bursts can be heard between transmissions or competing with a conversation.  Repeater sensitivity is affected.  During the summer of 1999, the odd digital burst was heard, and nothing more thought of it. Eventually, the emissions could be heard more often and would come and go. It was thought that a transmitter somewhere in the city, perhaps a mobile was intermittently spurious. Once spring 2000 came, the digital emissions became virtually continuous, prompting us to investigate.

Digital emissions don't mix with voice and are annoying.  It seems prudent that the long process of requesting a new repeater frequency (in Toronto, there aren't any available.. ) is undertaken.   There are also no guarantees that any other ham frequency may someday fall prey to such a device.!     

If the repeater is carrier squelch only, as many amateur repeaters are, every Compustar transmission within a few kilometers of the repeater site can be heard.     Should enough companies feel that the 445 to 450 MHz spectrum is a great place for their low power devices, in time amateurs may have to reverse their repeater inputs to reduce their interference levels.  This would cause the CompuStars out there some grief in returned product and customer dissatisfaction.  Their low power device would be competing with a 125W ERP transmitter!    It is hoped that this type of scenario can be avoided. Split reversal may cause issue to other distant 442.700+ repeaters.

This issue won't be isolated to Toronto.  Other North American repeaters on 442/447.700 will also be affected and may consider split reversal or a new frequency where possible.  442/447.700 may now be useful only as a rural linking pair or perhaps as a packet or other ham digipeater application.   To give up this frequency to the car alarm device, in essence providing them with a private North American frequency, would be precedence setting and unfortunate for the entire 445 to 450 band.  The way they take over this frequency with their semi-continuous operation and device proliferation is very unfair to the incumbent amateur radio community.  The UHF amateur band can slowly become a new ISM band.   

Consider also that there are many DGPS, crane control, telemetry and security devices in the amateur band.  Many are licensed, so there is some control where they go and to enable sharing of the band.  The Firstech car alarm company simply picked the repeater input side of the UHF amateur band.  How convenient for them!  Not FRS frequencies, 900 ISM, 390 MHz or even the common 433 MHz (also ham) frequency often used for low power telemetry.   It has to be noted that an identical alarm device called MagiCar operating on 433 MHz is made by the same Korean manufacturer.  This device has not been imported to North America but the 447.700 version is!?!?   

Please forward this web site address to your local repeater coordination council, owner of a 442.700+ repeater, or anyone this would concern.   Feel free to circulate for publicity on this issue and the ongoing commercial exploitation of the amateur band.   

PS.  This email is not intended to solicit sales of the said alarm systems. 

-  The alarm web page is www.compustar2w.com   

- The similar MagiCar Alarm that operates on 433 MHz instead of 447.700 MHz can be found at http://www.gfgroup.com.tw/new.htm 

-  To conduct your own search of FCC certification records, go to this site and enter in your search terms (example:  Frequency Range 445 to 450 MHz, Grant Code N99 for Firstech) https://gullfoss.fcc.gov/cgi-bin/ws.exe/prod/oet/forms/reports/Search_Form.hts?form=Generic_Search  

- ARRL Part 15 Web Page that discusses the complex issues surrounding Part 15 devices.

-  IC document RSS-210 http://strategis.ic.gc.ca/pics/sf/rss210.pdf for License-Exempt Regs.  Similar to FCC part 15. 

-  IC frequency search facility http://apollo.ic.gc.ca/english/main.html and type in 440 to 450 MHz to see LICENSED devices in the amateur band.  

-  See also www.howard.co.kr for another similar car alarm (operating frequency not known at this time.. stay tuned).   

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