Car Alarms Checking in on 447.700 MHz?

[K3PHL]

Hello all,

I took a scan of my local 440 band recently in Philadelphia and was suprised to hear bursts of data noise at varying signal strenghts almost constantly on 447.700. Doing some research, I came to a very interesting article about the COMPUSTAR car alarm and how it transmits on a frequency of 447.700. 447.700 happens to be the input frequency of repeaters on the 442.700/447.700 MHz pair.

What this boils down to is that any repeater using 447.700 as its input will have constant interference problems, especially if the repeater is running open carrier. It's amazing just how many vehicles are equipped with these units. I typically hear at least one burst lasting 10 seconds or more every minute on my vertical gain antenna in Northeast Philadelphia.

You can read all about the situation and the problems it has caused for the 442.700 repeater in Toronto here...


http://www.qsl.net/va3bmc

73 DE K3PHL
Steve

[KR6ER]

These burst on the 440 band are causing interference with repeaters hun? Has anybody called or wrote the manufactur and inform them that they might be in violation of Federal Law! Maybe you they should know. If my machine was being disrupted I would contact them.

[Anthony112]

I also found out that locally whenever listning to my ham radio (Will be licenced to talk within the next 3 days YAY! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif ) On frequency 147.29 I cant use the phone because it interferes on the radio

[N8YV]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (kr6er @ Mar. 27 2002,15:27)</td></tr><tr><td id="QUOTE">These burst on the 440 band are causing interference with repeaters hun? #Has anybody called or wrote the manufactur and inform them that they might be in violation of Federal Law![/QUOTE]<span id='postcolor'>
The scary part is, they may actually BE legal!! The 70-cm band is shared by radio amateurs and other users. Before wasting any time writing a letter to the manufacturer, I would first check-out the spectrum allocations for the area.

Pl tone the repeater! The keychain sized transmitters of the car alarm will hardly be enough power to cause interference to an ongoing QSO. On the plus side, think how much havoc you are causing the car alarm owners.

[kt6kt]

In Las Vegas, NV, they are on 434.790 MHz. #They have been DF'ed to cellular telephone stores, car dealerships, cars, churches, water pumping stations, and construction sites.

Some can be heard four (4) miles away from the transmitter (low power?).

Sometimes a fast scan ATV signal or Morse code practice appears on the frequency and the devices go away for a while!

Serge - kt6kt

kt6kt@juno.com

[m0tng]

We have this problem in the UK.
Be careful how you approach the matter, 70cms is Secondary status here and I know of One repeater group who have had to relocate a repeater because of it.

Regards
Stuart M0TNG

m0tng@btinternet.com

[N3SOZ]

Somewhat related to this, my wife got me a wireless thermometer for Christmas last year. #It has a remote unit that I have mounted outside and a base unit attached to the wall in the foyer. #The remote transmits to the base on 433.00 Mhz every 30 seconds. The operating freq. is advertised right on the base unit's case. #I know the mode isn't FM, based on listening for the transmission on my 70 cm HT. #Its my understanding that the 433 Mhz frequency is actually allocated for purposes like this (maybe a tertiary allocation?), but when dealing with shared spectrum we need to be aware of other users. #I don't know the signal strength of this thing, but since a covenant restricts exterior antennas in my neighborhood I'm not very concerned with wiping out anyone's weak-signal UHF work. #

Matt n3soz

[N5RLR]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (N8YV @ Mar. 27 2002,16:59)</td></tr><tr><td id="QUOTE"></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (kr6er @ Mar. 27 2002,15:27)</td></tr><tr><td id="QUOTE">These burst on the 440 band are causing interference with repeaters hun? #Has anybody called or wrote the manufactur and inform them that they might be in violation of Federal Law![/QUOTE]<span id='postcolor'>
The scary part is, they may actually BE legal!! The 70-cm band is shared by radio amateurs and other users. Before wasting any time writing a letter to the manufacturer, I would first check-out the spectrum allocations for the area.[/QUOTE]<span id='postcolor'>
In the US, the Military has primary allocation to 430/440
MHz; the Amateur Radio/Amateur Satellite Services have
secondary; and everything else is tertiary.

ON THE CONDITION that their transmissions do not
cause harmful interference to other, licensed/military
radio services.

('Course, if you wanted to be mean, you could key down
a couple hundred watts and see how many cars you could
make howl. http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif )

[WA3BXW]

I recently had trouble with one of the wireless car alarms operating on 434.790 mhz. During a cold night this would drift high and get into my 434.800 link receiver, and since the car was parked within line of site to the 500' tower my repeater is on it would cause quite a beat note with a user coming in via that link. The local office of the FCC (Langhorne, PA.) was contacted and went to the alarm distributor, where they acquired one of the units and sent it off to their lab to see if it was part 15 certified. They might be low power, but are they a pain in the .... when they park near your tower site. From everything I could read on the internet they are only to be sold in Europe, not the USA. If I receive a determination from the FCC I will post the results.

[kt6kt]

The device on 434.790 MHz described by wa3bxw is exactly what I have encountered in Vegas. I was not refering to the temp. sensors, weather stations, pool alarms, etc., operating on 433.9xx MHz.

I can use all the help I can get in gathering technical data to present a case to the FCC.

Serge - kt6kt
kt6kt@juno.com

[kc0idi]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (N8YV @ Mar. 27 2002,16:59)</td></tr><tr><td id="QUOTE">The scary part is, they may actually BE legal!! The 70-cm band is shared by radio amateurs and other users. Before wasting any time writing a letter to the manufacturer, I would first check-out the spectrum allocations for the area.[/QUOTE]<span id='postcolor'>
If a Part 95 divice causes harmfull interference, they have to chance

[k0xu]

Since these are Part 15 devices, they are not allowed to cause any harmfull interference to any licensed user and must accept any interference from a licensed used. The owner is responsible to remove them from the air. Just think about trying to tell your neighbor that he has to shut off his car alarm because it is interfering with you amateur radio contacts. Now the FCC is thinking of letting SAVI use devices with 10X the power & much longer transmissions on the band.

[AA2QA]

Well, I don't know how easy it might be .... I'd try to see if it could be coordinated with the input and output swapped. Oh, and raise the power and antenna gain for as much smoke as possible. Let the car alarms hear the repeater http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif



73 from Rochester, NY
Jim AA2QA

[KD6FBQ]

This sure explains why my 70cm transmissions somtimes set off car and home alarms in the neighborhood. As a side note, the little "tune-up" module I use for my Icom 706 also generates an ultrasonic tone that triggers some burglar alarms.
Apparently these kinds of alarms are tuned to
detect the sound of breaking glass, and the tone
is close enough to set them off. But the car alarms
are another thing entirely.

ONE DAY I WAS KEYING ON 144.10 QRP TO TEST MY RADIO, AND ALL OF A SUDDEN I HEARD A CAR ALARM GO OFF, AND IT WAS A CORV RIGHT NEXT TO US. SO THE OWNER TURNED IT OFF, BUT TO P.O. HIM I KEPT ON KEYING UP. LOL IT WAS FUNNY http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

You also have to think about the ignorant car alarm owners themselves. They have no idea whats going on (and probably don't care), nor should they be at fault for using a car alarm. The alarm manufacturer should be the one to take the heat, and they should get heat for being ingnorant.

[KD5JBN]

After reading your posts I did some investigation.. 50 watts from a GP-6 @ 38 feet will set off Mercedes, BMW, & Volvo alarms for 3 blocks http://www.qrz.com/iB_html/non-cgi/emoticons/wow.gif http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
Just thought you would like to know.. Thinking about driving by the MB dealership http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

[w1ctc]

In a recent exchange with the ARRL. One of these
434.790 car alarms was tested an was putting out
30 mw when the limit is 30 microwatts. Add an ant.
(also not legal for part 15) and you have QRM for
many miles. A complaint has been sent to the FCC.
Bob W1CTC