Prius causing other cars to malfunction?

[RonH]

I have noticed some self-interference while listening to AM in very weak signal conditions, ie multihop, multipath fading. It was clearly and easily identified with the MG coming on. Perhaps it is some faulty shielding in my 2004 or maybe the shark fin antenna, but its undetectable in normal AM or FM reception.

Edit: I would doubt that the I/F would affect a nearby car's radio even in the same reception conditions.

[ohershey]

<div class='quotetop'>QUOTE(abq sfr @ Aug 2 2007, 12:17 PM) [snapback]489476[/snapback]</div>

The limo undoubtedly had an FM modulator, one of those devices that will let you play your ipod through your FM stereo with no wires. Many of these were transmitting over the FCC limit for these devices and the FCC came down on the manufacturers. Newer modulators are at or below the FCC limit... not sure how many milliwatts that is. Regarding your ham neighbor, work with him to resolve the problem. You can install ferrite cores on your wires to reduce or eliminate the interference. He should know all about that. Part of being a Ham is working with neighbors to resolve any problem... no matter whether he is causing you interference, or you have a device causing him problems (aquarium heater, electric fence controller, etc). [/b]

We threw a couple of "Maintenance loop" coils into the speaker wires and that eliminated the problem - we're thinking that something about the way they were configured just happed to hit his freq spread just right. Either way, problem solved. He's not what I'd call a "good neighbor" type of operator. Three of the nieghbors on the court found some leads he had buried across their back yards at night. I don't know enough about RF stuff to guess WHY. Fortunately, it's not my problem - my neighbors are great.

[donee]

<div class='quotetop'>QUOTE(ZA_Andy @ Aug 2 2007, 04:18 PM) [snapback]489477[/snapback]</div>

Then he needs to be reported to the FCC because generating that kind of interference is against the conditions of his license - which would be revoked if not resolved at the operator's expense.

Not all Ham operators are competent, but by far the vast majority are, and take care not to cause this type of problem.
[/b]

The great majority of interferance traced to the consumer equipment that responds to legal emissions in close proximity. Ever live close to a AM broadcast station? Its kinda the same thing. Consumer equipment is built to the lowest cost standard, with little to no interferance engineering. Ham Equipment is built to get the ALL the signal on-channel, as the power limitations (not only legal, but economic) and low-performance locations hams operate from.

Desense is a common problem of receivers. When a strong, off channel (but within licensed frequency allocation) signal is nearby, the mixer may get a stronger signal from the antenna than from the reference (or local) oscillator within the reciever. In which case the normal mixing between the reference oscillator, and the intended signal stops. If the reciever had proper filter before the mixer, and higher power reference oscilator it would not happen.

Its true that there are some of CB operators running illegal amplifiers (called seatwarmers in the slang), and these amplifiers being illegal are not subject to FCC technical type acceptance before sale. Many poor designs, with high power spurious signals are common from these types of equipments.

This is a two-way street however. Many ham stations are interfered with by commercial equipment. A common problem is actually those reference oscillators mentioned above. Especially from a receiver on the FM broadcast band. Various poor FM receiver designs tend to emit strong signals. Another problem is poor shielding of CRT TV recievers. One can easily pick up noise within the amateur shortwave allocations from TV's, that can be quite powerful and drifts around.

And, its possible this is a geeky guy with unshielded computer boards running something in a Prius experiment. Take a look at Hobbit's dashboard - he has a prototyping plug board right there in front of the steering wheel. Not a ham at all, but could be emitting a signal much more powerful that the signal of the broadcast station in that location.

And there are multi-causes. Say the area has a strong paging transmitter. These transmitters are common on the taller buildings alongside a highway. They typically run 3000 watts, from tube type transmitters. The tubes wear, and start to throw out spurs. Or, a nearby lightning strike might damage internal components in the trasmitter, changing the operating conditions of tube power amp, or solid state circuits, resulting it it generating spurious signals. So, you can get desense in an area, that is not noticable, until a second source of noise comes along. Or even mix. The defective paging transmitter mixes the ham transmission, and reradiates it onto a new frequency.

Powerlines are another problem. When they work on 100 plus KV lines, there are leakage currents that radiate extremely strong RF noise. Its common for a whole neighborhood to loose over-the-air TV reception when this happens.

And then there is just mother nature. When I was in high school, my neighbor called me over and asked why I was causing all the interferance on channel 2. I told I could not be operating on Ham Radio while standing in his living room, so it was not me. I looked at his tv and clearly saw the interferance was TV sync bar related. Another TV station was interfering with channel 2. But how does that happen? Does the FCC not restrict TV broadcast territories to avoid interferance? Yes it does, but only to typical conditions. Every once and a while, the sun has more spots, which iononizes ionosphere more intensly. Channel 2 is the lowest frequency TV station, so during these times the shortwave skip can reach that high in frequency. On that day however, it was remarkable. I tuned his TV to channel 3 and we had a crystal clear station from New Brunswick coming in, and then to channel 4 and a weaker, but still watchable station from Nova Scotia. These stations are about 1500 miles from Chicagoland. But they were strong enough to intefere with local broadcasts.

There is also atmospheric refraction at the point in altitude where water condenses. This commonly causes long range FM broadcast reception. I have seen such propagation over several hundred miles, from ham stations with only a few tens of watts. Think what can happen to the local farm town station reception when a few megatwats of effective radiated downtwon Chicago FM station watts is bent back to earth by a strong refractive layer!

And there is also Auroral scatter. It just sounds like noise, but its the signal reflected off the Aurora Borealis. The high energy of the auroral particles completely scrambles the modulation of any station, but one sending morse code. In which case the signal sounds line noise switching off and on.