interesting read about interference

I learned something too today, seem like wires in a simple electric devise that's otherwise off can cause a parasitic drain of the batteries thru inductance.
 
A similar thing happened to a Ham radio friend who parked at a Home Improvement store with his new car. He got out, clicked 'lock' and then the car unlocked itself. He had to use the key to lock the car or it would unlock. He discovered through time that this happened only in certain spots near where their wireless security cameras were mounted, a well as near their main front doors. As any radio nut can tell you, RFI can exhibit some really strange effects and it can come from very unexpected places :eek:

Phil
 
A similar thing happened to a Ham radio friend who parked at a Home Improvement store with his new car. He got out, clicked 'lock' and then the car unlocked itself. He had to use the key to lock the car or it would unlock. He discovered through time that this happened only in certain spots near where their wireless security cameras were mounted, a well as near their main front doors. As any radio nut can tell you, RFI can exhibit some really strange effects and it can come from very unexpected places :eek:

Phil
That's better than the person I knew who stopped to let someone out of the car, unloaded their luggage for them, then went to get back in the car and heard the door locks operate, he was locked out of the car with the keys in the ignition, no spare key to manually unlock the doors, and the engine still running!
 
That's better than the person I knew who stopped to let someone out of the car, unloaded their luggage for them, then went to get back in the car and heard the door locks operate, he was locked out of the car with the keys in the ignition, no spare key to manually unlock the doors, and the engine still running!

Not sure where I learned this, but I always lower the drivers window if I'm getting out the car while it's running unless there's someone else in the car.
 
I also lower drivers windows partially before getting out of a car, forget which vehicle it was it was easy to bump the door lock on the way out....but it became habit.

Hell, but I'm the guy who called a locksmith to get into my car after I threw some stuff in the trunk and thought I also put my keys in there.
It turned out they were in a pocket I never put them in. :) (found them after I paid the fee)
 
Not sure where I learned this, but I always lower the drivers window if I'm getting out the car while it's running unless there's someone else in the car.
I never get out of the car while the engine is still running, not since I did it with a Renault, then when I jumped back in it interpreted the forward motion created by my jumping in as a trigger to turn off the electronic handbrake (car was accelerating). The car was parked on a steep Swiss Alpine pass at the time so I found myself with the car rolling forward, my feet not over the foot brake and an electronic handbrake which refused to operate because the car managed to reach 4kph before got my fingers on the button... I shall never accept another Renault either!
 
Yeah, RFI is an interesting problem at times. Years ago I used to be 'on call' and have to carry a pager (before the days of cell phones) on a rotating basis with a few other employees. For a time every day on the way home I would get a page from seemingly random numbers. It turned out that my normal commute was near a major airport and some of their equipment (radio, radar, ???) was causing the problem. Only solution was for me to change my route those weeks when I was on call - which had the unfortunate side effect of adding about 15 minutes to my travel time.
 
This problem is also why i argue against the use of wifi, if not for the security aspect of it one really should try to keep the use of it to a minimum.

I myself dont like to have any "radios" going as that alone can be used for a lot of things i do not want to be part off, and i really wish there was some way to have MAC addresses change them self ever so often.
 
After 33 years of dealing with TV and radio interferences of all sorts and many times having to go search for them by walking in the streets with an antena, a field strength meter and a portable TV set, this doesn't really come as a surprise to me. ;)

It kinda reminds me of a case I had in a zone of difficult TV reception where one day everybody stopped receiving the Ch. 3 of the VHF I Band due to an interference. After checking that none of the antennas of the area was causing it, we decided to shut down the power of all the apartments that were being affected one by one until we found the cause. It turned out to be a Grundig VCR's power supply! :eek: At first we thought it was because the VCR was connected to the antenna but no, all it took to completely block the picture with interferences was being connected to the mains anywhere inside the apartment!
A few years later the same thing happened with a brand new Grundig satellite receiver but that time, through our supplier, we managed to bring an engineer from Grundig Portugal here to witness the problem in loco.

Some years ago AV transmitters (AVT) started being interfered by microwave ovens, so much that the AVT manufacturers had to change their equipments' frequency from 2.4GHz to 5.8GHz. Otoh, the 2.4GHz AVT's Ch. 1 (they have 4 channels to choose from) interferes with WiFi. :confused:
It's very common to hear people say that they can receive police or fire department communications on their "made-who-knows-where-and-apparently-with-on-paper-only-interference-compliances" baby monitoring devices.
Recently I discovered that even 4G can interfere with the LNB's for satellite reception, so much that manufacturers started making LNBs with 4G filters. And 4G is broadcasting between 800 and 900MHz, while Ku band satellite services broadcast between 10.6GHz and 12.75GHz!

WAFM, that's what I say. (n)
 
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A local Ham friend tells the tale of when he worked on the only local hill (which now has 21 major-power transmitters on it) and a field supervisor used to look over his shoulder as my friend worked. One day my friend brought an old Geiger counter to work and left it clicking away at the end of his workbench. The supervisor showed up, investigated the clicking sound, and promptly left for home never to bother my friend again :ROFLMAO: Those old units weren't very discriminating, and it was picking up what was probably a safe level of radio and TV radiation, not something from a nuclear energy source. My friend knew that bit his boss didn't :p

One of the requirements for US Hams now is that you do a RF safety evaluation for your station. You have to calculate the minimum safe distance between people and your antenna on the frequencies you operate on based on a formula the FCC developed. One part of this is striking: The higher you go in frequency using the same radiated power output, the longer the minimum safe distance becomes. And here we are filling as many of the higher frequencies as we can with wifi, cellphone, remote controls, TV and radio, the sum total of which in areas of dense usage is far beyond the same FCC safety limits I'm required to adhere to :eek: Yet the people clamor for more and they get it without having a clue of what it is doing to them. We are all frying our brain cells permanently in the name of convenience- perhaps that's what happened to cause all the idiot drivers we have on the roads now :rolleyes:

Phil
 
There's a RFI hot spot in Homebush (Sydney) thats known to completely shut down BMW's if they drove past it.
 
One part of this is striking: The higher you go in frequency using the same radiated power output, the longer the minimum safe distance becomes.

Phil
And do you know why? Take a look at the low and high frequencies' wave shape and you'll know why. ;)
 
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