Part one of this pair explained that a PL tone, a DPL code and a digital system protect nothing about who can hear you, and this part takes up the other half of the problem, which is who else is on the channel and what you are entitled to do about it. Most of what gets reported as interference turns out to be a misprogrammed radio, a failing power supply or an authorized co-channel user on a good propagation day, and the small remainder that is deliberate is handled by people with authority you do not have. This is written to be handed to a new supervisor.

Accidental, incidental, intentional, and the word the FCC uses

Before anything else happens, somebody has to decide which of three situations is in front of them, because that decision determines who gets the phone call, what evidence has to be preserved in the next few hours, and whether this is a maintenance ticket or a potential enforcement matter. The three buckets I use are accidental, meaning another radio user genuinely does not know they are on top of you, incidental, meaning something is radiating as a byproduct of doing another job entirely, and intentional, meaning a person is doing this on purpose. Those are working words from engineering and field practice rather than regulatory categories, and it is worth being clear about that before a supervisor writes one of them into a complaint.

The term the Commission itself uses is harmful interference, which is defined in the definitions section of Part 2 of the FCC rules and carried through the service rules including Part 90, and the definition turns on effect rather than on intent, covering interference that endangers the functioning of a safety service or that seriously degrades, obstructs or repeatedly interrupts a radio service operating in accordance with the rules. Intent shows up in the statute instead. Section 333 of the Communications Act, 47 U.S.C. 333, prohibits willful or malicious interference with the radio communications of any station licensed or authorized under the Act or operated by the United States Government, and the FCC’s own jammer enforcement material describes that section in exactly those terms. Read the current text of both the Part 2 definition and Section 333 rather than my summary of them, because your complaint should use the Commission’s vocabulary and not mine. In practice this means you can describe the effect on your system with confidence from day one, while a claim about somebody’s intent has to wait for evidence that almost never exists at the start.

Accidental interference is the largest category by a wide margin in everything I have worked. A mutual aid partner selects the wrong zone and transmits on your dispatch channel for three days before anyone connects the two facts. A contractor’s radio comes back from a shop with a tone that does not match what the shop was told. A neighboring system’s technician programs a test channel into a fleet and forgets to remove it. A co-channel licensee two hundred miles away, entirely lawful and entirely unaware of you, arrives in your receivers for forty minutes on a morning when a temperature inversion has built a duct over the coastal plain, and departs when the duct breaks up. VHF low band brings the same experience by way of ionospheric skip in the spring and summer, and that one is normal physics rather than a fault in anybody’s equipment.

Incidental interference is the category that costs the most technician time, because the source is a device that has no idea it is a transmitter. Intermodulation products formed when two or more strong signals mix, either in a nonlinear junction at a crowded tower site or inside your own receiver front end, land on a frequency neither parent signal occupies. A failing switching power supply, an LED lighting driver, an old fluorescent ballast, an arcing connector on a utility pole, and a cable television distribution line with a cracked shield all radiate broadband trash or a discrete carrier, and the leaky cable line is one the FCC’s Enforcement Bureau does handle as its own subject matter under the heading of cable signal leakage. Part 15 devices are labeled with the terms of their own existence, which is that the device may not cause harmful interference and must accept any interference received, so the neighbor’s equipment has no protected status and also no obligation to be quiet in a way that helps you today. Intentional interference exists, it is real, and it is rare enough that treating an unexplained signal as deliberate in the first hour is a mistake I have watched cost agencies both goodwill and time.

What to document, and the recording that is about to be overwritten

This is the most practical section in the article, and it is the part a communications officer should turn into a one page form. Record the date, the start time and the end time to the minute, with the clock you used named, because the console clock, the CAD timestamp and a supervisor’s phone can differ by enough to matter when somebody later compares your log to a recording. Record the frequency or the talkgroup, and if it is a trunked system record whether the problem appeared on one talkgroup or on the control channel, since those point in different directions. Record which sites or repeaters were affected, and record just as carefully which ones were not, because the list of sites that were clean is often the single most useful diagnostic fact in the whole report. Record the receiving equipment and where it was: a portable in the parking lot of Station 3, a mobile on the interstate, the dispatch console position, the base radio in the training room.

Describe what was heard in plain terms and resist the urge to interpret. Write that there was a steady unmodulated carrier with no audio for about ninety seconds, or a buzzing noise that rose and fell in level roughly twice a second, or music, or a voice speaking a language the listener could not identify, or a short data burst that repeated at intervals of about ten seconds. Note explicitly whether it was voice, tone, carrier or noise, and note whether your repeater keyed up on it or whether it only appeared in the receivers. Note whether users could break in over it or whether the channel was unusable. What you should not write is the word jammer, because that word is a conclusion, and once it appears in the first paragraph of a report it colors everything that follows and it is the first thing an engineer or an FCC field agent will discount.

Repetition and correlation are what turn a collection of complaints into a solvable problem. Write down whether it happens again, and at what times, and then look for what else in the world runs on that schedule. Interference that starts at 6:45 every weekday morning and stops at 4:30 in the afternoon is following somebody’s shift or somebody’s business hours. Interference that appears within a few minutes of local sunrise and sunset most days is following propagation. Interference that occurs whenever a particular overhead door opens, or whenever a specific piece of shop equipment starts, or only when a certain unit is parked at a certain address, has named itself. Collect witnesses by name and unit rather than as a count, because a field agent or a coordinator will want to talk to the person who heard it, and a supervisor’s summary of what four unnamed firefighters said is much weaker than two people who will describe what came out of their own portables.

The recordings are the evidence, and I want to be blunt about the timing here. Voice logging recorders in dispatch centers retain audio on a schedule and then overwrite it, and that schedule is set by agency policy, by contract, by the size of the storage, and in some places by state records retention law, so it might be thirty days, ninety days, a year, or something else entirely, and nobody should assume. Everything else in the interference report can be written next week without much loss. The request to preserve the audio cannot, because the file that proves the channel was unusable for six minutes on a Tuesday evening deletes itself on a timer that started running the moment the transmission ended. Send the preservation request in writing to the records custodian or the dispatch supervisor the same day, name the exact date, the exact time window with a margin on either side, and every channel or talkgroup involved, and ask for an exported copy held outside the normal retention cycle rather than a promise that the original will be left alone. Ask what file format you will get and confirm that somebody can actually play it, since an export nobody can open is not evidence.

Who to call, and why the answer depends on who you are

Start inside your own organization every time, because the great majority of interference is resolved at the system administrator’s desk or in the radio shop and never becomes anybody’s enforcement matter. A trunked system manager can look at site alarms, control channel activity and affiliation records and often explain in twenty minutes what a field crew has been guessing about for a week. A radio technician with a service monitor can tell you whether the signal is on your input or your output, whether it is on frequency or off, and whether the product you are hearing could be intermodulation from two known transmitters at your own site. Your maintenance vendor is next if the system is under contract, and this is the moment to have their after-hours number on the same page as everything else rather than in one person’s phone. If your own equipment is the source, which happens more often than agencies like to record, the whole matter ends there and the only thing worth writing down is what failed and what was changed.

Your frequency coordinator is the next step for a licensed land mobile system, and coordinators are underused. The FCC certifies frequency coordinators by radio pool and publishes the list, so a public safety agency works through a certified public safety coordinator and a business works through a certified coordinator for the Industrial or Business pool. A coordinator can look at the assignments around you, identify the licensee whose transmitter is probably in your receiver, and open a licensee to licensee conversation that resolves the problem without a complaint being filed by anybody. You can do part of that yourself in the FCC’s Universal Licensing System by searching the frequency and the geography to see who else holds an authorization nearby, which is public information and is the right way to learn that the signal you have been calling an intruder is a lawful co-channel user who was licensed before you were.

The FCC is the step after that, and the route differs by who you are. The Commission’s Enforcement Bureau handles interference through its Spectrum Enforcement Division together with its regional and field offices, and the Bureau’s own published material says its highest priority is interference affecting those who protect the public and preserve security, naming FAA air traffic control and navigation, Coast Guard search and rescue, EMS, police and fire. The Commission’s interference resolution page currently directs public safety and enterprise licensees to file electronically through its radio frequency service interference complaint portal, and directs consumers and members of the public to the Consumer Complaint Center run by the Consumer and Governmental Affairs Bureau. A public notice in 2019 announced that single intake point for public safety and enterprise interference complaints, and it also told those users to exhaust their own efforts first and to use any industry specific reporting mechanism that applies to them, such as the one used by 800 MHz licensees. Portal names and web addresses change, so start at fcc.gov and follow the Enforcement Bureau pages rather than trusting a link printed in an article, and do not let anyone at your agency invent a form number or a hotline number to put in a plan.

Two routes differ enough to name separately. The FCC’s guide to public safety enforcement states that the Commission has entered into a memorandum of understanding with APCO to resolve public safety related interference complaints in the first instance and that the Enforcement Bureau encourages public safety agencies to use it, so a fire or EMS agency should expect that path rather than assuming a federal agent arrives on the first call. A law enforcement agency has one option the others do not, since deliberate interference with public safety communications is a criminal offense under the law of many states, which means a police or sheriff’s agency can open a criminal case in parallel with the FCC referral, and I would have that conversation with the prosecutor’s office rather than relying on anyone’s recollection of the state code. A private business licensee has no special channel and works internally, then through its vendor, then its coordinator, then the enterprise route at the Commission. An FRS or GMRS user has no system administrator and no coordinator at all, which leaves documentation, a channel change, and the consumer complaint route in the narrow case where the conduct really does look willful, and that reality is part of what the licence in that service actually is.

A realistic account of what happens next matters more than the flowchart. Complaints are triaged, and the Commission has fewer field offices and field staff than it once did, a reduction the FCC itself pointed to when it proposed the amateur volunteer monitoring arrangement discussed later in this article. Cases that move do so over weeks and months rather than days, except where there is an immediate threat to safety of life, and the Commission’s published guidance for broadcasters says plainly that once an investigation starts the FCC does not discuss its status, which is a good thing to warn a chief about before the chief starts asking. Outcomes range from a letter of inquiry or a notice of unlicensed operation through citations and monetary forfeitures under Section 503 of the Act, and the more serious remedies including seizure of equipment, injunctive relief and criminal prosecution require coordination with the Department of Justice, which the Commission notes means the timing is not entirely within its control. Most interference never reaches any of this and should not, because it was a codeplug, a power supply or a neighbor.

What not to do, and what not to say on the air

Do not confront the suspected interferer on the air, and that includes a warning, a demand for a call sign, an announcement that this frequency is licensed to the fire department, and above all a threat, because none of those things has ever cleared a channel in my experience and every one of them creates a record that works against you. Everything transmitted on your system is evidence in the same proceeding you are trying to build, and it is being received by an unknown number of people, some of whom record continuously and some of whom archive those recordings and publish them. When an investigator finally listens to the audio you preserved, the useful version is six minutes of an unexplained carrier over a crew trying to work, and the unhelpful version is the same six minutes with a captain arguing over it, because the second version invites a question about who was interfering with whom.

Do not transmit over the other station, key over it, hold the channel to deny it, or retaliate in any of the ways people think of within the first hour. Section 333 does not contain a self defense clause, and on a shared assignment the user who deliberately transmits to prevent another authorized user from communicating is the one with the problem. This is the single fastest way for a complainant to end up as a respondent, and it is entirely avoidable. What you should do operationally is execute the fallback you already planned, which means moving the affected traffic to an alternate channel or another site, telling dispatch what moved and when, and continuing to work while somebody else diagnoses the cause. Moving the traffic does not solve the interference and it is still the correct decision, and the move itself belongs in your documentation with its own timestamp.

Do not go and find the person. This one gets argued with, so I will give the reasons rather than just the rule. A member of your agency driving around with a radio looking for a transmitter is not conducting an investigation, has no authority to be anywhere he would not otherwise be allowed, may be walking toward a person who has already demonstrated poor judgment, and can compromise a case that would otherwise have been made cleanly by people whose evidence will survive a challenge. Do not identify a suspect publicly, or in a staff meeting, or in a social media post, before there is something to support it, because a wrong name causes an injury you cannot take back and a right name announced early tells the subject to stop and to dispose of equipment. Do not discuss an active referral on an open channel, on an unencrypted talkgroup, or in a public meeting whose minutes are published, and keep that conversation in the internal chain with your legal counsel and your public information officer.

The reasoning behind all of it is the same. Enforcement, when it happens, is built on a clean record consisting of your logs, your preserved recordings, your equipment’s observations and the testimony of witnesses who described what they heard rather than what they concluded. Every transmission your agency makes about the situation is a contribution to that record, and a channel full of accusations is a record that raises doubts about the complainant. There is also a practical reason that has nothing to do with law, which is that a certain number of unauthorized users are testing for a reaction, and the reaction is the reward.

What your license entitles you to, by class

On FRS and GMRS, channels are shared and hearing other people is the normal, designed, expected condition of the service. A GMRS licence conveys no exclusive right to a channel, and the Part 95 rules for the service require cooperation in sharing the channels rather than granting anyone priority, which is worth reading in the current text of Part 95 subpart E if a family or a club is making plans around it. The channel arrangement also constrains what is possible, since the interstitial channels commonly numbered 8 through 14 are limited to very low power in the current rules while the main channels support higher power and GMRS adds repeater pairs that FRS does not have. A GMRS licence itself is straightforward, with no examination, a term of ten years, and coverage that extends to the licensee’s immediate family, and the application fee has been thirty five dollars rather than the older seventy dollars since the Commission’s revised fee schedule took effect in 2022. The sources I checked in 2026 still show thirty five dollars, and you should confirm the current figure in the Universal Licensing System before quoting it to your members, since fee schedules change without any announcement that reaches radio users.

On a Part 90 licensed frequency, the first thing to establish is which kind of assignment you hold, because the answer changes the meaning of the signal you are hearing. Part 90 defines itinerant operation as operation of a radio station at unspecified locations for varying periods of time, and itinerant frequencies exist precisely so that work that moves around does not require a new coordination every time. Section 90.138 of the rules covers applications for those frequencies in the Industrial and Business Pool and says two things that settle the question: such an application need not be accompanied by evidence of frequency coordination, and users should be aware that no interference protection is provided from other itinerant operations. If you are working on an itinerant channel and another lawful user turns up on it, you are experiencing the arrangement you licensed into, which is congestion rather than interference.

A non-itinerant assignment is a different animal, because it is tied to specified fixed locations or to a defined area of operation, it was coordinated against the other assignments in the region, and the coordination process applied separation and protection criteria that assume everyone stays inside what they were granted. Even there, the general position under Part 90 is that land mobile frequencies are shared, with exclusivity available only in the specific circumstances the rules provide for and only in some bands, which part one of this pair covered. What the coordinated assignment gives you is a basis for saying that a particular signal should not be present at that place with that strength, and that basis is what makes a coordinator’s intervention or an FCC complaint meaningful. On a shared or itinerant channel, another user is not evidence of anything, and on a coordinated site specific assignment, another user might be exactly the evidence you need.

A reader who does not know which they hold can find out this week without help from a consultant. Pull each of your call signs in the Universal Licensing System and read the authorization itself, which shows the frequencies, the emission designators, the power, the antenna structures and the locations or the area of operation, and mark on the printout which frequencies are itinerant and which are tied to a place. Then ask your license administrator or the coordinator who prepared the application what protection, if any, was contemplated for each frequency, and write the answer next to it. That single marked page is what tells a new supervisor whether a strange voice on channel four is a problem or a fact of life, and it is also the first document a coordinator or a field agent will ask you for.

Jammers and GPS disruption: what they look like from your side

Signal jammers exist, they are inexpensive, and they are illegal in the United States. The Commission’s jammer enforcement material sets out the statutory basis, and the pieces are worth naming precisely because people repeat them approximately: Section 301 of the Communications Act requires that transmitters be licensed or authorized, Section 302(b), codified at 47 U.S.C. 302a(b), prohibits the manufacture, importation, marketing, sale and shipment of noncompliant devices including jammers, and Section 333 prohibits willful or malicious interference with licensed or authorized stations or with United States Government stations. The Commission’s enforcement documents in jammer cases cite those statutory sections together with implementing rules in Parts 2 and 15, Section 501 provides for criminal sanctions including imprisonment, and Section 503 provides for forfeitures. The FCC’s guidance has been consistent that operating one is not available to state or local government users, including law enforcement, and if anyone at your agency has been told otherwise by a salesman, read the Commission’s current jammer enforcement material before another word is spent on it. This article says nothing about how such a device works, how one is obtained, or how one is used, and that boundary is deliberate.

What matters to a communications officer is recognition from the victim’s side, and the symptoms are unglamorous. A persistent carrier occupies the channel with no modulation and no identification. The noise floor rises so that signals which were solid last week are now buried, and your coverage map effectively shrinks. Receivers will not unmute at all, or they unmute and then mute in the middle of a transmission, and portables show a full signal indicator while producing nothing usable. Coverage collapses in one geographic area while every other part of the system behaves normally, which is the pattern that most often makes people suspect a device, and it is also the pattern produced by a failing amplifier at one site or by a piece of consumer equipment in one building. That ambiguity is the whole reason the documentation and the radio shop come before the accusation, because from the receiver’s point of view a deliberate carrier, an unattended stuck microphone and an arcing sign transformer are hard to tell apart.

GPS belongs in the same section because modern land mobile systems lean on it for timing as much as for position, and when it degrades the failure often does not look like a radio problem at first. Simulcast systems require a precise common time reference to keep transmitters aligned, so a loss of GPS lock at a site can produce distortion and dropouts in the overlap areas while each transmitter individually appears healthy. Vehicle location goes wrong in ways dispatchers notice before technicians do, with positions freezing, jumping several miles, or reporting a unit somewhere it has never been. Timestamps in logs, in CAD and in the recording system can drift, which is a records problem as well as an operational one. Site equipment typically alarms on loss of GPS and then runs on its internal holdover for a limited period before performance degrades, and whether that alarm reaches your dispatch center or only your vendor’s network operations center is a question worth answering before you need the answer.

The reporting route for GPS is not the same as for a radio channel, and it is worth writing into the plan correctly. The Coast Guard Navigation Center, NAVCEN, is the designated point of contact for operational GPS support to the civilian community, and it publishes a GPS problem report form and posts reports after review by its staff. NAVCEN’s own guidance says it can confirm the status of the constellation and determine whether approved GPS testing is going on in your vicinity, and that it cannot help with equipment problems, which is why it asks you to rule out a single-device fault first. GPS.gov states that a suspected disruption due to illegal jamming should be reported to the FCC in addition to NAVCEN, and that civil aviation users inside the United States should contact the FAA, which publishes notices about known GPS service disruptions. Scheduled interference testing coordinated among the Department of Defense, the FAA and the Coast Guard is a real and common explanation for a regional GPS anomaly, and checking for it costs one phone call or one web page. Nothing in this article addresses how GPS interference or spoofing is carried out, and I do not answer that question.

Who can actually find a transmitter, and what volunteers may do

A signal on a conventional analog or digital frequency can be located, and it is important that a new supervisor understand that so nobody either despairs or decides to try it personally. The people who do this properly include the FCC Enforcement Bureau’s field agents, who have the equipment, the training and the authority to act on what they find, and the Commission’s own published enforcement documents describe cases of exactly that kind. In one 2019 matter documented in the Bureau’s published record, agents traced GPS interference to a particular vehicle and asked to inspect it, the individual refused and drove away, and the interference was observed to leave with the vehicle. That kind of account is available in the Commission’s enforcement releases for anyone who wants to see how the work actually proceeds, and reading two or three of them is better preparation for a chief than any summary I can write. State and regional players contribute as well, including your statewide interoperability coordinator’s office, your system vendor’s engineering staff, utility spectrum managers who deal with this on their own systems, and county or city radio shops with a technician who has been chasing intermod since the analog era.

Amateur radio operators are genuinely valuable here and their value is easy to misdescribe, so I want to be specific about it. Experienced amateurs bring receivers, spectrum analyzers, attenuators, antennas and a habit of careful listening, and many of them have spent years characterizing signals for sport. They can help describe what a signal is doing, which is the part most agencies are weakest at, by documenting whether it is a steady carrier or modulated, what its timing looks like, whether it appears on harmonically related frequencies, and whether it correlates with something in the environment. They can assist a licensee or an agency under that agency’s direction and tasking, which in most places means through an existing ARES or RACES relationship or a written agreement, and the site’s article on amateur operators as a disaster communications force multiplier covers how that relationship should be structured.

The amateur service also has a formal monitoring arrangement that deserves accurate description rather than folklore. The ARRL Volunteer Monitor Program is a formal agreement between the FCC and ARRL, approved by the ARRL board in July 2018 and implemented under a memorandum of understanding signed in 2019, under which volunteers trained and vetted by ARRL monitor the amateur bands and collect evidence that can be used to correct misconduct or to recognize exemplary operation. ARRL’s description says flagrant violations are referred to the FCC by ARRL for action under FCC guidelines, and that the FCC gives enforcement priority to cases developed through the program rather than requiring ARRL to route them through the ordinary online complaint process. The program replaced the older Official Observer program and has been overseen by Riley Hollingsworth, K4ZDH, a retired FCC special counsel. Two limits follow from that description and are the whole point of naming the program here. Volunteer Monitors document and report, and the enforcement determination is the Commission’s. The program’s scope is the amateur bands, so it is not a mechanism for your Part 90 problem.

The prohibitions apply to every volunteer, however experienced and however well intentioned, and they should be stated to a volunteer group in plain words before anyone is asked to help. A volunteer has no enforcement authority and cannot make an enforcement determination. A volunteer must not transmit on frequencies he is not authorized to use, and an Amateur Extra licence authorizes nothing on a public safety channel. A volunteer must not confront a suspect, must not conduct a search, and must not enter property, whether that property is a driveway, a business or a fenced tower compound. A volunteer must not represent himself as acting for the FCC or as an agent of your agency, and if he is assisting your agency his role is to observe and report to a named person in your chain. An agency that puts those limits in writing before the first callout gets the benefit of volunteer skill without the liability that comes from an enthusiastic person improvising.

The licensing decision: when exclusivity is worth buying

Agencies that keep having interference problems eventually ask whether the answer is a licensed frequency of their own, and sometimes it is. Life safety dispatch traffic that has to work at three in the morning on the worst night of the year belongs on an assignment that was coordinated for the purpose, with protection criteria behind it and a record you can point to when somebody else’s signal shows up. If your channel is genuinely loaded, if your users cannot get in when they need to, if your fireground traffic is competing with a landscaping company on an itinerant pair, then the cost of coordination, licensing, engineering and equipment is buying something real. The constraint in most of the country is availability rather than money, because in congested areas the spectrum simply is not there in the band you want, exclusivity under Part 90 is limited to the specific circumstances the rules allow, and the answer arrives after months of coordination work rather than in a budget cycle. Ask your certified coordinator what is actually available near you before the conversation goes any further, because that answer sets the boundaries of every other option.

The counter-case matters more than it usually gets credit for, and my example is off-road groups. A club or a trail group that wants to be heard is served well by GMRS, where any member can obtain an individual licence with no examination for a modest fee, with a ten year term and family coverage, using handhelds and mobiles the members may already own, and where a well sited community repeater can cover a surprising amount of country. On that service, hearing the group two ridges over is a benefit rather than a nuisance, because the stuck vehicle wants to be heard by whoever is closest, and the group coming up the trail wants to know what is around the next corner. Spending years chasing an exclusive assignment for traffic whose entire purpose is to reach strangers would be the wrong project, and it would produce a system that works less well for the mission than the one available for the price of a licence application. Note one eligibility detail before planning around it: new GMRS licences under the current Part 95 rules are issued to individuals, with earlier non-individual licensees grandfathered, so a club, a business or a commercial guide service should verify current eligibility in Part 95 subpart E rather than assuming an organizational licence is available.

The same reasoning cuts the other way for traffic that must not be casually shared, and this is where the two parts of this pair meet. If the problem is that outsiders can hear you, no amount of licensing solves it and encryption is the only mechanism that does, which is the subject of part one and of the site’s articles on encryption. If the problem is that you cannot get on the channel when it matters, licensing is exactly the right tool and encryption does nothing for you. Deciding which problem you have is a five minute conversation that agencies skip, and skipping it produces the two familiar failures, which are an agency that bought an expensive exclusive channel and still says sensitive things in the clear on it, and an agency that encrypted everything while its users still cannot get a word in on a crowded pair.

The underlying point is about how the question gets framed at the table. Exclusivity is a requirement to be justified with traffic, timing and consequence, and it is not a status to aspire to because it sounds more professional than sharing. The useful question is what the traffic actually is: who has to hear it, how quickly, with what reliability, on whose equipment, and what happens if a stranger is talking when the call comes in. A group whose honest answer is that being overheard is fine and being reachable is essential should stop shopping for exclusivity and get its members licensed. A fire department whose honest answer is that a dispatch channel has to be available every time should be talking to a coordinator this quarter and should have the interference documentation described earlier in hand when it does.

What to do at your agency

• Ask your system administrator or radio shop to write on one page the exact retention period of your voice logging recorder, the name and title of the person who can place a preservation hold, and the vendor’s after-hours number, and put that page inside the dispatch supervisor’s binder this month.
• Have the dispatch supervisor test the preservation process on an arbitrary five minute window of ordinary traffic, and confirm that you receive a playable exported file, that you know its format, and that it is held outside the normal overwrite cycle.
• Have your license administrator pull each of your call signs in the FCC Universal Licensing System, print the authorizations, and mark on each printout which frequencies are itinerant and which are tied to a specified location or area of operation.
• Get the name and current phone number of the certified frequency coordinator who prepared your assignments from your license administrator or radio shop, and file it with the license printouts so a new supervisor does not have to find it during an incident.
• Add one item to the next officers’ or communications committee meeting that is already on the calendar: what a member says on the air when an unknown station is on the channel, which is nothing about that station, and which alternate channel the crew moves to instead.
• Write one paragraph into your existing communications SOP stating that suspected deliberate interference is documented and reported up the chain rather than discussed on the air, and naming the position that authorizes a coordinator contact or an FCC complaint.
• Ask your system administrator whether each simulcast site alarms on loss of GPS lock, how long each site holds over before performance degrades, and whether that alarm reaches your dispatch center or only the vendor’s network operations center.

Takeaways

• Accidental, incidental and intentional are field triage words rather than regulatory categories, and the FCC’s operative term is harmful interference, defined by effect in the definitions section of Part 2 of its rules, while intent appears in Section 333 of the Communications Act at 47 U.S.C. 333.
• Accidental interference from misprogrammed radios, wrong tones and lawful co-channel users on good propagation days accounts for most reports, and incidental interference from intermodulation, failing power supplies, lighting equipment and leaking cable television lines accounts for most technician time.
• Documentation should record time to the minute, the frequency or talkgroup, which sites were affected and which were clean, a plain description of what was heard without the word jammer in it, whether it repeats, what it correlates with, and the names of the people who heard it.
• The preservation request for logging recorder audio is the only urgent item in the whole report, because retention periods vary by agency and the recording overwrites itself on a schedule that does not wait for your investigation.
• Escalation runs from your system administrator or radio shop, to your maintenance vendor, to your FCC certified frequency coordinator, and only then to the Commission, and the FCC’s 2019 public notice on its interference complaint intake told public safety and enterprise users to exhaust their own efforts first.
• The FCC’s Enforcement Bureau handles interference through its Spectrum Enforcement Division and its field offices, its published material puts interference to public safety and safety-of-life services at the top of its priorities, its guidance says it does not discuss investigations once they begin, and the most serious remedies require coordination with the Department of Justice.
• Nothing about the situation is improved by confronting the other station on the air, transmitting over it, or going to find the person, and each of those acts can convert a complainant into a respondent or spoil a record that would otherwise have supported enforcement.
• A GMRS licence conveys no exclusive right to a channel, and Part 90 itinerant assignments come with the rules’ own statement that no interference protection is provided from other itinerant operations, so the meaning of another user on your channel depends entirely on what your authorization says.
• Signal jammers are prohibited under Sections 301, 302(b) and 333 of the Communications Act with penalties available under Sections 501 and 503, and the symptoms on the victim’s side, a persistent carrier, a rising noise floor and coverage that collapses in one area, look the same as several ordinary equipment failures.
• GPS supports timing as well as position in modern systems, so simulcast alignment, vehicle location and time stamping can degrade together, and the civilian reporting route runs through the Coast Guard Navigation Center, with the FCC additionally for suspected illegal jamming and the FAA for civil aviation users.
• ARRL Volunteer Monitors, operating under a memorandum of understanding between the FCC and ARRL implemented in 2019, monitor the amateur bands and collect evidence for referral, and neither they nor any other volunteer holds enforcement authority or may transmit on frequencies they are not authorized to use.