Minature AM transmitters - attenuation?

The neighbor's behavior might be coincidence. So to greatly reduce the probability of it being explained as coincidence, I think a LOT more testing of the OP's conjecture is needed first. The transmitter should be turned on and off through at least 1000 spaced cycles, with careful observation of the neighbor during each cycle. :) I might consider reducing that probability to zero in the limit if I were ornery. ;)

Jon

Thanks for the suggestion Jon, however I don't particularly want the ghost hunters around and I'd like to stay on good terms with the neighbours!

peter

Thanks John, I hadn't thought of that.

I took the antenna wire out (prototype board) and did a couple of short transmissions without a problem. I then left the transmitter on for a few seconds to change the data that was being sent and the doorbell starting ringing again....

Hopefully they will go out for the afternoon so I can experiment a bit more.

peter

Does this only take place while sending the data or does it also happen with a carrier only?

If it's data related, see if you have an option to turn down the drive on the carrier, you could be over driving it and generating lots of splatter.. (harmonics)

Jamie

Jamie

The transmitter only transmits when it has data going to the 'data' terminal - it's not continuously transmitting a carrier without any data. The transmitter modules are pretty 'black box' without much scope to adjust.

I've tried reducing the supply voltage, but I think next door have taken the batteries out of their doorbell now (transmitting on full power when they went to walk to the dog didn't seem to set anything off) so it's hard to tell if it makes a difference.

peter

peter,

You might consider purchasing a 433MHz wireless doorbell of your own. I dimly recall the prices on these things being in the $10-20 range ... Ah! Home Depot has a Heath Zenith Kit for $13, but no mention of frequency.

The advantage, assuming that the one you find mimics your neighbor's doorbell, is that you could test with a very short antenna or none at all and still see whether you were causing a problem. (Ideally you'd find a doorbell of the same make and model as your neighbor's, but this might not be the ideal time to ask about this. )

This is an area where I'd advise caution, because, as someone operating radio transmitting equipm,ent (and thus responsible for the interference caused by it)), it's not just something between you and your neighbor. First, others may be affected, not just the one neighbor you know about, and second, if anyone gets ticked off enough and calls in the FCC, it sounds like the FCC will be able to figure out fairly quickly who the "interfering" party is.

In the instructions accompanying the transmitter/transceiver module there should be some sort of note describing the maximum antenna length. You should check this to make sure you aren't exceeding the FCC-approved length.

You might also want to review this section of the ARRL 'Web site:

Radio Frequency Interference (RFI)

and the pointers to FCC information here:

FCC RFI Information

Sorry... I'm not trying to rain on your parade, but I suspect you'd be a little ticked off if the situation were reversed -- if, say, your neighbor's doorbell started triggering loud buzzing sounds from your 200-watt stereo speakers.

Hope this helps...

Frank McKenney

Go knock on the neighbor's door with your transmitter in your hand, and tell him that you think your transmitter is triggering his doorbell. Politely ask him if it's OK to press your button right then to test it.

If it does, then apologize profusely and either tune your tx/rx to a different frequency, or buy a transmitter that's already on a different frequency.

And 20 cm of antenna might violate FCC rules, depending on what band it's operating on; see part 15 of the FCC rules.

Hope This Helps! Rich

Perhaps the FCC doesn't apply where he is.

Tom

Their doorbell should be using a coded signal and be mostly immune to accidental triggering.

that would work.

The real problem is with the doorbell. but reducing or attenuating the antenna should stop the accidental triggereing

AIUI the regulations on the 433Mhz band say that signals should be intermittant, not constant. The band is used for several different remote-control tasks and while one transmitter is running it's unavailable for other tasks.

You could try putting a reflector between the transmitter antenna and the doorbell location, close to the transmitter antenna. The idea is that the waves radiated from the antenna toward the neighbor are reflected in the opposite direction before they have traveled even one wavelength (about 28"). See

You should be able to build a simple corner reflector from the information there.

Ed