Date: 202007
Local time of day: 0601-1200
Location: ZKC.ARTCC, KS
Flight conditions: Marginal
Weather elements / visibility: Rain
Aircraft: No Aircraft
Operator: Other ALL
Operating under: Other ALL
Mission: Other ALL
Flight phase: Climb; Cruise; Descent
Airspace: Class E ZKC
ATC / advisory: Center ZKC
Reporter organization: Government
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Distraction; Communication Breakdown; Workload
Anomaly: ATC Issue All Types
Detector: Person Air Traffic Control
When detected: In-flight; Routine Inspection
Result: Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic; Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Company Policy; ATC Equipment / Nav Facility / Buildings
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: The frequency at the transmitter site began emitting bursts of unintelligible transmissions. These transmissions caused difficulties in being able to transmit to and understand aircraft on frequency. As we were able to turn off the site at the sector to avoid hearing the repeated noise; numerous pilots stated there was continuous noise on frequency causing interference and affecting communications. The incident was reported to the Operations Manager and directly to the SOC. We were advised a technician would be out to examine the site; but that it would take approximately 2 hours for the tech to get there. I conveyed the importance that this issue be addressed as soon as possible as it was directly impacting operations and creating problems. Specifically; as we were told to turn off the site; we were only able to use two other L sites to talk to low-altitude aircraft. As such; aircraft on the west side of the sector below approximately 6;000 ft. could not hear us at all. As it was a weekend; one of the airport's tower was closed and a part 135 carrier was unable to reach us on the ground to receive their IFR clearance as they normally would. Instead; the aircraft departed VFR and tried calling us in the air to get their IFR clearance. We were able to hear the aircraft; but the aircraft could not hear us until approximately 4 minutes after they departed. I then went to the SOC and advocated that a NOTAM be issued to advise aircraft of the frequency issue. Throughout the day; numerous aircraft were lost on frequency as they could not hear us; and we could not hear them. As a result; we had to relay through multiple aircraft to broadcast for the 'missing' aircraft. This created increased workload; increased frequency congestion; and often confusion as pilots were incorrectly understanding the callsign of the aircraft we were looking for; the frequency we were requesting the aircraft switch to; or both. In one instance; an aircraft was cleared for an instrument approach at an airport and not heard from again until approximately 15 minutes later after FSS called and advised the aircraft cancelled IFR. The controller was unable to get a response from the aircraft after issuing; 'report cancellation of IFR on this frequency or with FSS; change to advisory frequency approved.' Later in the afternoon; as precipitation became an issue; aircraft were requesting to deviate while we continued to have aircraft relay for other aircraft that we could not talk to. This presented an unnecessary frequency congestion issue and increased controller workload significantly.Usually; if a frequency is having issues; changing transmit/receive sites or utilizing another frequency with similar coverage can temporarily solve most problems. In this case; however; as the interference was affecting the entire frequency; such actions would not work. Additionally; without any other frequency available with similar coverage; we were left with having to use aircraft to relay. Whether a temporary modification on the switching equipment needs to be made to reallocate a frequency that could work; or if there needs to be an analysis of existing frequencies and their respective coverage areas; something must be done to prevent similar situations again. This issue has caused a degradation of ATC services; increased workload on behalf of both pilots and controllers; and presented a significant safety issue.




Synopsis: Center Controller reported a frequency transmitter site failure caused a lack of ability to communicate with aircraft directly in a portion of their airspace increasing their workload during a busy period due to weather deviations.