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Frequency Interference

Frequency Interference

Frequency Interference

(OP)
I recently noticed my two garage door remote controls were not working. Before I had a chance to call for service and after resetting the remote controls, my neighbor called and told me that 7 houses adjoining each of us had the same problem. He had contacted the company that installed his and was told there was nothing wrong with his garage door openers and someone in the area had some device emitting a large amplitude signal in the bandwidth the remote controls were operating in. I contacted the FCC and was told by a very rude rep that they did not investigate issues like this and to contact my local police and report it. Right!!!. The only recourse I can think of doing is either renting a spectrum analyzer with a directional antenna and locating the source or replacing the unit. Can anyone think of anything else I can do? Even finding this source, how can I enforce the elimination of the signal?

Any help from you guys would be greatly appreciated.

Thanks

RE: Frequency Interference

My first thought would be to find your local hams.  Explain this to them. I would wager that they would be all over this for the fun of it.  They play fox and hound games trying to find moving transmitters and such.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Frequency Interference

It's probably the US Military (according to reports). USAF Radar for protecting Life, Liberty And The Pursuit Of Happiness.

Assuming that this is the case here, it's actually their frequency so there's not much to do except contact the local garage door vendors to see if they can offer you an external receiver on another frequency.

This has been in the tech news recently in various locations so you might want to dig into it using the above info to help confirm the cause. Google garage door and radar to see what you see...

RE: Frequency Interference

The first thing anyone would want to know is what the  operating frequency is. Ham operators can't do anything without an appropriate antenna! The instruction booklet for the garage opener should state the frequency.

RE: Frequency Interference

To contact Hams, search for American Radio Relay League" or ARRL and your city.


http://www.arrl.org/

RE: Frequency Interference

Thanks VE1BLL.

I just can't imagine anyone using a Military frequency for a garage door opener! The Military are not known for low power operation.

I suppose these devices are coded so your opener doesn't open your neighbour's garage door. Then we are just talking about raw carrier wave power jamming the signal. This means either getting really close or using a highly directional yagi (which at 390MHz would be huge!)

Interestingly, this is "nobody's fault", ie nobody will pay for it except Joe Public.

RE: Frequency Interference

Sorry Logbook I think VE1BLL is right. That's right military is not known low power operation and that is exactly what the problem may be. Garage door opener frequency has to be in one of the ISM cahannels.
Around all ISM channels there are fixed governement channels. If one of the governement channels bleeds over ISM channel there may bean interference because the governement channel is more likely running at maximum FCC power permitted (1,000 miliwatt) while Garage Door is transmitting at less than 30 miliwatts power level, but at the same frequency of Military transmission (or one of harmonics).
Regards,
Bursa

RE: Frequency Interference

225 to 400 MHz is primarily military in the USA. In some countries, the local spectrum regulator has basically turned the band over to the military to manage. I've always been mildly surprised that unlicensed low power systems were allowed in the band.

Then again, garage door systems are the realm of super-regenerative receivers; about as low tech as you can get.

RE: Frequency Interference

Bursa,
perhaps there is an error in the translation.

When I said ...
"I just can't imagine anyone using a Military frequency for a garage door opener!"

This was an idiomatic way of saying "I can understand that some people are so dumb that they would do this"

RE: Frequency Interference

The FCC notice said that the Garage Door Folks chose these frequencies, although allocated to the government/military,  since there was little activity in these bands.  The garage door opener transmitters are low power and unregulated and low power users have no recourse to interference from allocated users.

RE: Frequency Interference

I do not know for sure, but I will bet that the frequencies allocated for these garage door systems are listed as "secondary service" by the FCC.

In effect it means, you can certainly use that frequency, but if the primary user (Military) is causing interference, tough luck.

It also means that if you push your garage door opening button, and it interferes with the military service, the FCC or the military will track you down, and shut you down.

A friendly ham operator can probably confirm the source, but I doubt if there is anything you will be able to do about it, if it is a government produced source of interference.

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