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Author Topic: Car Alarm sounds on 2M 50 watt transmit.  (Read 799 times)
KG6FGX
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Posts: 13




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« on: May 09, 2001, 04:46:24 PM »

I just completed installation of an Alinco DR-605TQ in my truck.  Everything works great except for high power 2M transmit.    When I key the mike, the car alarm will sound.  Low power 5W transmit does not cause the problem, 440 transmit at 35W or 5 W also is not a problem.

The Alarm "Black Box" is located 6" directly below the radio.  It would not be possible to relocate the Alarm "Black Box."

The problem also occurs transmitting with a handheld radio in the truck.

Does anybody have any suggestions, or will I have to live with it.

Thanks,
Jim
KG6FGX
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N2HBX
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Posts: 162




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« Reply #1 on: May 09, 2001, 10:14:45 PM »

The proximity of the radio to the "black box" is probably not the problem.  The problem is RF getting into the alarm receiver (I assume it is the type with a remote switch).  Using the HT in the cab causes the problem also because although the power level is lower, the proximity of the antenna is producing a substantial RF field.

You don't mention what type of antenna you are using.  If possible, I would try to relocate the antenna as far away from the "box" as possible.  You could experiment with a mag mount in different locations to see if it makes a difference.

One more possibility...a friend of mine had a car alarm that used a voltage sense circuit to determine if one of the protected doors was opened causing the dome light to come on. It would sense the voltage drop caused by the load of the dome light and trip the alarm.  It didn't take much of a drop to set it off.  See if you can determine if this is the case with your alarm and then check to see if your radio is causing enough of a voltage dr
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WB2WIK
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Posts: 20636




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« Reply #2 on: May 10, 2001, 01:00:45 PM »

Not to be sarcastic, but I find the easiest solution is to permanently disable the alarm, and I have done so on every vehicle I've owned, plus those owned by wives and girlfriends, or anyone I cared about.

The problem with these systems (or most of them) is that the remote entry lock mechanism and alarm are tied together using common circuitry.  The alarms are annoying, nobody pays attention to them, professional car thieves can disable them in a moment...so what purpose are they actually serving?  The remote "keyless" locks are very convenient, but in many cases can be an awful problem (read more) and in some cases, they have proven to be life-threatening, or even life-taking.

Most of the keyless lock systems latch into the "locked" position if 12Vdc power is removed from the system; that is to say, the "normal state" of the door locks is LOCKED.  It takes some current to keep them OPEN.  This is logical, since you don't want the locks draining your car battery if you're parked a long time.  The problem with this method is that as your car battery dies -- and one day, it will -- the very last thing that will occur is that all your doors will lock.  Now your doors are locked, and the battery is dead.  If you happen to have a key, you can still get back in to the car.  If not, oh well.  But if you happen to be IN the car when the system fails, you can be locked in.

An average man has sufficient strength, usually, to unlock the door by overcoming the resistance of the lock; however a small woman might not, and in any case someone who is incapacitated by an accident, faintness, stroke or other malady probably will not be able to unlock the door and get out of the car.  If such an event occurs as the result of a collision, this can be a very hazardous situation.

The television news program "60 Minutes" has already highlighted stories involving drivers or passengers who died following collisions, purely because they were unable to open doors that were automatically locked when the 12V power system in the affected vehicle failed.

Since that automatic locking mechanism is electrically part of the "keyless entry" and alarm subsystems, I, for one, will never allow myself or any loved ones to drive a vehicle employing this active circuitry.  In my car, I disabled the alarm/keyless entry mechanism on the day I took delivery, and encourage others to do the same.

73 & safe driving!

Steve WB2WIK/6
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KG6FGX
Member

Posts: 13




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« Reply #3 on: May 11, 2001, 04:18:09 PM »

Thanks for everyones input, your comments got me thinking in a different direction and I eventually solved the problem.
From your comments, I realized the problem was originating at the antenna and not the radio itself.  I then began thinking about a previous concern I had, I have a glass sunroof and the antenna is mounted directly behind it (see the post in this forum "Does RF emissions and glass sunroof = baldness 3/7/01."  I realized RF emissions were entering the passenger compartment of the vehicle, overloading the alarm receiver and causing it to sound.
A few pieces of aluminum foil over the sunroof confirmed it, the alarm no longer sounded with the foil in place.  I made the foil permanent by applying it with 3M adheisive spray to the backside of a clip in sunscreen provided with the sunroof, problem solved.

Again, thanks for your suggestions, they eventually led me to solving the problem.  
Jim
KG6FGX
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