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How do I report RFI to a mobile station?

Jul 30th 2011, 08:29


Joined: Apr 4th 1998, 00:00
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This may be one of those infamous stupid questions, but how do you go about reporting an RFI source to responsible parties? For example, I enjoy mobile HF ops on my commute to and from work. Along that commute route, there is one intersection with multiple traffic lights and the controller completely whipes out 75m, 40m and some sections of 20m, with varying distances depending on frequency. For 75/80m phone its pretty much within 1/4 mile of the intersection, for 40m and 20m its only a few hundred yards, but still, its frustrating to have to turn the volume down and/or turn the radio off as I pass thru or sit at this intersection and miss either important or interesting information that's passed during this time.
And on a separate, but related, topic, what about Cable leakage? When scanning repeaters for activity along this same route, and another I take to visit with my children, I pick up TV broadcasts from cable in specific locations along the commute. These effect not only the programmed repeater pairs, but the UHF receive frequencies programmed into my scanner. Are we, as HAM's, supposed to be susceptible to this spurious emissions, or immune? Who would be responsible for something like that? The Cable company, the business owner nearby where the interference is happening, or the homeowner where it occurs? Or, should it just be ignored and move on?
Aug 8th 2011, 19:35


Joined: Apr 4th 1998, 00:00
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First, let me start by saying that under FCC Part 15 rules, it is the operator of a device that is responsible for correcting a problem of “harmful interference” to a licensed radio service. Paraphrasing a bit, “harmful interference” is also defined in the rules as a repeated disruption of intended radio communications.

Most Part 15 interference cases involving Amateur radio are argued on the basis of harmful interference. Specified emissions limits in these cases rarely ever come into play. In order for the FCC to act in these cases, the interference must meet the FCC’s criteria to be harmful. This includes that the interference must be repeated. There must also be intended radio communication, and interference must be strong enough to disrupt that communication.

It is also important to understand that manufacturers of Part 15 unintentional emitters are required only to meet certain specified missions limits. These limits are high enough that interference can occur to nearby receivers in some cases. If and when harmful interference does occur, the burden then falls on the device operator to fix it – not the manufacturer.

Obviously, the first order of business when interference occurs is to find the device operator. In the case of power lines, your local utility would be the operator in most cases. Likewise, report the cable interference to your cable company. In these cases, you should generally start by filing a complaint through the normal customer service channels. And finally, a consumer device in your neighbor’s home would be something to address with your neighbor, even if the noise is being conducted onto and radiated by the neighborhood power lines.

Most interference sources are actually found right in the complainant’s residence. It’s always a good idea to turn off the main breaker to your house while listening with a battery portable to the interference. Assuming that the source is in your neighbor’s home, you can start by printing a couple pamphlets. They may be very helpful before you discuss the interference with him or her. Here are the links:

1) Information for neighbors of hams:

2) Locating procedure:
Also available as a Word file at:

Obviously, the importance of diplomacy cannot be overstated when approaching your neighbor. I generally recommend that you approach them with a radio in hand whenever possible. If the noise can be heard in the AM broadcast band, use an AM receiver. Demonstrating the problem with something they recognize as an ordinary radio is generally a good idea. It’s more likely to help them appreciate the interference as a problem, not just for you but other neighbors as well.

Be sure the noise is active when you knock on the door. Let them hear it but not so loud that it will be offensive. Tell them this is the problem you are experiencing and you believe the source may be in their home. Don't suggest what you think the cause might be. If you're wrong, it often makes matters worse. Show them the Neighbor Info sheet and tell them it will only take a minute to eliminate their house. Be sure to review the locating tips procedure if they seem uncertain about what needs to be done.

Note: In some cases, RFI from a device in a home can signal a potential shock or fire hazard. You may wish to discuss this with your neighbor if he or she seems reluctant to cooperate by finding the source.

In conclusion, I’d like to make a few comments about mobile stations. Under federal law, it is the FCC and only the FCC that has the responsibility to enforce its rules. As I said earlier, many RFI complaints can hinge of what the FCC determines to be harmful interference as defined by its rules. Historically, the FCC has not been particularly sympathetic toward mobile stations driving past point sources of interference. Usually they determine that the interference is not repeated when the mobile station can drive past it. Should you decide to file a complaint of interference to your mobile station, you should be prepared to demonstrate that it meets the FCC’s definition of harmful should it get to the stage of an FCC field investigation.
Aug 9th 2011, 00:58


Joined: Jul 25th 2011, 14:25
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Under FCC rules, manufacturers of unlicensed emitters of noise must meet authorization requirements and usually must meet certain limits on emissions. In the case of HF (below 30 MHz), the manufacturer must meet conducted emissions limits.

The limits are set rather high by radiocommunications standards, and interference for a couple of hundred feet from a "legal" device is quite possible.

When this interference is to a fixed Amateur station, the rules are pretty clear -- noise at the levels you describe is pretty clearly harmful interference and this could be addressed by the FCC. However, as MG point out, the FCC has not taken the same approach with a mobile operator and the FCC feels that it is not repeated and that because the mobile operator can drive away, it does not "seriously degrade." I can't say that I completely agree with the FCC, but I can at least understand the logic.

However, having said all that, if this is strong a quarter mile away on 75 meters, I have to wonder whether the emissions are legal. If FCC were to follow suit with what it did in the BPL rules, it would classify the environment that the controller and light are in as "commericial." As ARRL gets reports of interference from various devices, it often is able to contact the manufacturers involved and sometimes can get some relief. Sometimes not, though, and we have to look closely at available staff time as we set prorities.

As to the cable leakage, the same basic principle applies. The cable company must meet limits on radiated emissions from cable that would typically be about S9 to a moible whip on the street. If the leaks are above this level, your cable company SHOULD want to know, as those are leaks they must fix to pass their biannual cumulative leakage index tests. Below that level, it's a matter of "harmful interference."

ARRL does have contacts in the the cable industry that can help resolve problems, so if looks as if the leaks are above S9 or so, contact and he can let you know how to proceed.

Ed Hare, W1RFI
Technical forums moderator
Aug 16th 2011, 21:40


Joined: Apr 4th 1998, 00:00
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Total Posts: 0
I will add one thing to the above posts. In addition to the info above you have 4 problems to overcome: the company who manufactured the light, the electric company who provides electricity to the light, the city itself as owner and the FCC Itself....

The Interference source could be being sent out by the light and its method of install . Or the problem could be a bad electric pole at that corner. OR if that were not bad enough any combination.

Plus in addition of who to blame you have to remember that the FCC just might not do anything because its just a bad stop light.

But if the FCC does get interested you gotta know that city, electric company and the manufacturer of the light are going to be pointing fingers at everyone else but themselves so they do not have to spend money to fix the situation.

I think the bottom line is going to be that it will be far better to just not engage in conversation for that brief period of time and then pick up the conversation when you have passed that bad intersection.


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